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Air Quality Review andAssessment – Stage 4

Report to Oxford City Council

netcen/ED49226/R/1455 Issue 1April 2003

Title Air Quality Review and Assessment – Stage 4

Customer Oxford City Council

Customerreference

Confidentiality,copyright andreproduction

File reference ENTC ED49226

Report number AEAT/R/1455

Report status Issue 1

John AbbottNational Environmental Technology CentreBuilding E5Culham Science CentreAbingdonOxon.OX14 3EDTelephone 01235 46 3051Facsimile 01235 46 3038

AEA Technology is the trading name of AEA Technology plcAEA Technology is certificated to ISO9001

Executive Summary

The UK Government published its strategic policy framework for air quality management in1995 establishing national strategies and policies on air quality which culminated in theEnvironment Act, 1995. The Air Quality Strategy provides a framework for air qualitycontrol through air quality management and air quality standards. These and other airquality standards1 and their objectives2 have been enacted through the Air QualityRegulations in 1997 and 2000. The Environment Act 1995 requires Local Authorities toundertake an air quality review. In areas where the air quality objective is not anticipatedto be met, Local Authorities are required to establish Air Quality Management Areas toimprove air quality.

The first step in this process is to undertake a review of current and potential future airquality. A minimum of two air quality reviews are recommended in order to assesscompliance with air quality objectives; one to assess air quality at the outset of the AirQuality Strategy and a second to be carried out towards the end of the policy timescale(2005). The number of reviews necessary depends on the likelihood of achieving theobjectives. Each of these two reviews is split into components. For the first round of airquality review and assessment, there are four components. The components are: Stages 1to 3; and Stage 4 and Action Plans. Stage 4 and Action Plans are normally completed inparallel. Not all local authorities have to complete all the components.

This report is equivalent to a Stage 4 air quality review and assessment for Oxford asoutlined in the Government’s published guidance. Oxford City Council plan to submit theirAction Plan in autumn 2003.

Oxford City Council has completed a Stage 3 Air Quality Review and Assessment. Theresults of this indicated that exceedences of the annual mean objective for nitrogendioxide (NO2) were likely on the building facades along many of the streets in Oxford Citycentre. As a result of the Stage 3 air quality review and assessment, Oxford City Councildeclared an Air Quality Management Area (AQMA). The determination of the geographicalboundary of the Air Quality Management Area took into account:

• The likelihood of exceeding the objectives;• The nature of public exposure (long term /short term) at relevant locations;• The physical boundaries of properties and other features;• The ability to describe the area in words.

Oxford City Council declared a single city centre AQMA for convenience and ease ofdescription.

1 Refers to standards recommended by the Expert Panel on Air Quality Standards. Recommended standards areset purely with regard to scientific and medical evidence on the effects of the particular pollutants on health, atlevels at which risks to public health, including vulnerable groups, are very small or regarded as negligible.2 Refers to objectives in the Strategy for each of the eight pollutants. The objectives provide policy targets byoutlining what should be achieved in the light of the air quality standards and other relevant factors and areexpressed as a given ambient concentration to be achieved within a given timescale.

The general approach taken to this Stage 4 assessment was to:

• Identify the improvement needed in concentrations of nitrogen dioxide at selectedreceptors in the Air Quality Management Area, including the receptors where thegreatest improvements were needed;

• Collect and interpret additional data to support the Stage 4 assessment, includingdetailed traffic flow data around locations where exceedences of the NO2 objectivewere predicted;

• Consider recent continuous monitoring and diffusion tube measurements;

• Identify the contributions of the relevant sources to the exceedences (local traffic,background sources, and other relevant sources);

• Use monitoring data from the NO2 continuous monitors located at the Town Halland at St Ebbes to assess the ambient concentrations produced by the road trafficand to calibrate the output of the NO2 modelling studies;

• Model the concentrations of NO2 around the AQMA, concentrating on the locations(receptors) where people might be exposed over the relevant averaging times ofthe air quality objectives;

• Consider three scenarios to improve air quality and identify the improvements inair quality that might be possible for nitrogen dioxide;

• Present the concentrations as contour plots of concentrations and assess theuncertainty in the predicted concentrations;

• Consider any changes that are need to the existing Air Quality Management Areas;

• Consider the feasibilities of implementing the options in a very simple way.

The assessment confirmed that the objective for 2005 for nitrogen dioxide of 40 µg m-3

as an annual mean will not be met at many locations throughout Oxford City centre. Thearea affected includes areas of housing and educational facilities and broadly correspondsto the existing AQMA. A number of small changes to the boundary are recommended sothat Oxford City Council can maintain their conservative approach to the definition of theAQMA. The following table summarises the changes that might be needed to the existingAir Quality Management Area as the result of this Stage 4 review and assessment.

Name of area modelled Changes recommended to the existing AirQuality Management Area

City centre None. Consider public exposure over the annualaveraging time

St Clements and the Plain Extend the AQMA along St Clements Street asfar as Morrell Avenue and approximately 120 malong Cowley Road from the Plain

St Giles and theUniversity Science Area

Extend the AQMA along the east side of St Gilesas far as Woodstock Road

Junction of ParksRoad/Banbury Road.

None recommended, but consider potentialexposure of members of the public and reassessin the updating and screening assessment ifthere is significant exposure

Botley Road NoneSpeedwellStreet/Littlegate

Extend the AQMA approximately 30 m furthersouth along St Aldates

The reductions needed in annual mean NO2 concentrations to ensure that concentrationsall relevant receptors in the AQMA did not exceed 40 µg/m3 were:

36 µg m-3 on Queen Street33 µg m-3 on George Street33 µg m-3 on High Street15 µg m-3 on St Aldates9 µg m-3 at St Clements/The Plain27 µg m-3 at the Station Shops at Park End4 µg m-3 on Speedwell Street

The source apportionment work identified emissions of oxides of nitrogen (NOx) fromtraffic on roads close to the AQMA as the important source where emissions might bereduced. Bus stops and buses moving in slow congested traffic are the most significantsource in the city centre, where poor dispersion in street canyons accentuates theproblem. The general background of NOx cannot be easily reduced except by nationalmeasures. Emissions of NOx from local traffic accounted for approximately 80 % of theoxides of nitrogen concentration at the Town Hall.

Oxfordshire County Council have suggested a range of measures to reduce emissions inthe city centre:

Further enforcement of the bus gates might reduce congestion and allow a freerflow of traffic. This measure alone might at best reduce concentrations at theTown Hall to 44 µg m-3 in 2005 compared to the objective of 40 µg m-3. Themeasure has the potential to markedly reduce concentrations, but reduction incongestion alone without reducing vehicle numbers would not be sufficient. Busboarding time improvements may also be effective in reducing the effectsassociated with traffic congestion.

Switching off bus engines at bus stops also has considerable potential to reducenitrogen dioxide concentrations. It is estimated that nitrogen dioxideconcentrations might be reduced to 39-45 µg m-3 at the Town Hall. This measurealone may not be sufficient to prevent exceedences of the objective.

Many of the buses operating on Oxford city centre are relatively modern andmeet the Euro II standard. It is estimated that further upgrading to the Euro IIIstandard would reduce the forecast nitrogen dioxide concentration at the TownHall to 48 µg m-3. Further upgrading of the bus fleet will not be a sufficientmeasure alone to meet the objective at the Town Hall.

Further improvements are possible as the result of extending the bus qualitypartnership. In particular, further consideration should be given to the potentialexposure of members of the public living close to the bus stops. High nitrogendioxide concentrations close to bus stops may not be a relevant consideration ifthere are no residential areas nearby.

A number of developments have the potential to affect air quality in the citycentre including the Westgate development, relocation of the station andrelocation of the Gloucester Green coach station. However, none of thesedevelopments is likely to be implemented before 2005.

Acronyms and definitions

AADTF Annual Average Daily Traffic FlowADMS Urban an atmospheric dispersion modelAQDD an EU directive (part of EU law) - Common Position on Air Quality

Daughter Directives, commonly referred to as the Air Quality DaughterDirective

AQMA Air Quality Management AreaAQS Air Quality StrategyAP Action PlanAUN Automatic Urban Network (DEFRA funded network)base case In the context of this report, the emissions or concentrations predicted at

the date of the relevant air quality objective (2005 for nitrogen dioxide)CO Carbon monoxided.f. degrees of freedom (in statistical analysis of data)DETR Department of the Environment Transport and the Regions (now DEFRA)DEFRA Department of the Environment, Farming and Rural AffairsDMRB Design Manual for Roads and BridgesEA Environment AgencyEPA Environmental Protection ActEPAQS Expert Panel on Air Quality Standards (UK panel)EU European UnionGIS Geographical Information SystemHA Highways Agencykerbside 0 to 1 m from the kerbLimit Value An EU definition for an air quality standard of a pollutant listed in the air

quality directivesn number of pairs of dataNAEI National Atmospheric Emission InventoryNO2 Nitrogen dioxideNOx Oxides of nitrogenNRTF National Road Traffic Forecastppb parts per billionr the correlation coefficient (between two variables)receptor In the context of this study, the relevant location where air quality is

assessed or predicted (for example, houses, hospitals and schools)roadside 1 to 5 m from the kerbSD standard deviation (of a range of data)SO2 Sulphur dioxideTEMPRO A piece of software produced by the DEFRA used to forecast traffic flow

increasesUWE AQMRC University of the West of England Air Quality Management Resource

Centre

Contents

1 INTRODUCTION TO THIS STAGE 4 AIR QUALITY ASSESSMENT ......................11.1 PURPOSE OF THE STUDY ............................................................................................................................11.2 BRIEF EXPLANATION OF A STAGE 4 AIR QUALITY REVIEW AND ASSESSMENT ..................11.3 OVERVIEW OF APPROACH TAKEN.........................................................................................................11.4 RELEVANT DEFRA DOCUMENTATION USED......................................................................................21.5 NUMBERING OF TABLES AND FIGURES................................................................................................21.6 POLLUTANTS CONSIDERED IN THIS REPORT ....................................................................................21.7 UNITS OF CONCENTRATION USED AND CONVERSIONS TO OTHER UNITS.............................21.8 COPYRIGHT OF THE MAPS ........................................................................................................................2

2 THE UK AIR QUALITY STRATEGY.........................................................................32.1 OVERVIEW OF THE PRINCIPLES AND MAIN ELEMENTS OF THE AIR QUALITY

STRATEGY........................................................................................................................................................42.1.1 National Air Quality Standards .................................................................................................................... 42.1.2 The difference between ‘standards’ and ‘objectives’ in the UK AQS ......................................................... 42.1.3 Relationship between the UK National Air Quality Standards and EU air quality Limit Values ................ 62.1.4 Changes to the UK National Air Quality Standards..................................................................................... 62.1.5 Policies in place to allow the objectives for the pollutants in AQS to be achieved...................................... 72.1.6 Timescales to achieve the objectives for the pollutants in AQS .................................................................. 7

2.2 AIR QUALITY REVIEWS – THE APPROACHES AND EXPECTED OUTCOMES ...........................72.3 LOCATIONS THAT THE REVIEW AND ASSESSMENT MUST CONCENTRATE ON .................12

3 STAGE 4 AIR QUALITY REVIEW AND ASSESSMENT AND ACTIONPLANNING .............................................................................................................14

3.1 THE RELATIONSHIPS BETWEEN A STAGE 4 AIR QUALITY REVIEW AND ASSESSMENTAND AN ACTION PLAN ...............................................................................................................................14

3.2 DEFRA GUIDANCE ON STAGE 4 AIR QUALITY REVIEW AND ASSESSMENT..........................143.3 ACTION PLANS..............................................................................................................................................153.4 STAGE 4 AND ACTION PLAN TIMESCALES.........................................................................................15

4 INFORMATION USED TO SUPPORT THIS ASSESSMENT .................................174.1 MAPS AND DISTANCES OF RECEPTORS FROM ROADS .................................................................174.2 ROAD TRAFFIC DATA.................................................................................................................................174.3 AMBIENT MONITORING............................................................................................................................174.4 EMISSION FACTORS USED IN THIS REVIEW AND ASSESSMENT................................................184.5 LIAISON WITH OTHER ORGANISATIONS ...........................................................................................18

5 STAGE 4 REVIEW AND ASSESSMENT FOR NITROGEN DIOXIDE....................195.1 STANDARDS AND OBJECTIVES FOR NITROGEN DIOXIDE ...........................................................195.2 KEY FINDINGS OF THE STAGE 3 REVIEW AND ASSESSMENT.....................................................195.3 AREA DECLARED BY OXFORD AS AN AIR QUALITY MANAGEMENT AREA..........................205.4 MONITORING ................................................................................................................................................22

5.4.1 Monitoring data included in the Stage 3 report .......................................................................................... 225.4.2 Additional monitoring after the Stage 3 Review and Assessment was completed..................................... 245.4.3 Changes in nitrogen dioxide concentrations since the Stage 3 review..................................................... 265.4.4 Factors used to predict future diffusion tube concentrations from current concentrations......................... 275.4.5 Comparison of the monitoring results with the relevant air quality objectives .......................................... 29

5.5 OVERVIEW OF THE AIR QUALITY MODELLING FOR THIS STAGE 4 ASSESSMENT............315.5.1 Summary of the model used in this Stage 4 assessment............................................................................. 31

5.5.2 Validation and verification of the model.................................................................................................... 325.5.3 Bias adjustment of the model ..................................................................................................................... 35

5.6 IMPROVEMENTS NEEDED IN AIR QUALITY ......................................................................................365.6.1 The improvement that is needed – general points ...................................................................................... 365.6.2 Areas of predicted exceedence of the air quality objectives considered in this Stage 4 assessment .......... 36

5.7 SOURCE APPORTIONMENT OF ‘BASE CASE’ PREDICTIONS........................................................475.7.1 What is the ‘base case’? ............................................................................................................................. 475.7.2 Receptors considered ................................................................................................................................. 475.7.3 Sources of pollution considered ................................................................................................................. 47

5.8 OPTIONS CONSIDERED TO IMPROVE AIR QUALITY AND THE EFFECTS OF THOSEOPTIONS..........................................................................................................................................................49

5.8.1 The options (Action Plan scenarios) considered ........................................................................................ 495.8.2 Bus gate enforcement................................................................................................................................. 505.8.3 Switching off bus engines while stationary................................................................................................ 505.8.4 Higher emission standards ....................................................................................................................... 515.8.5 Bus and taxi quality partnerships ............................................................................................................... 525.8.6 Bus boarding time improvements.............................................................................................................. 525.8.7 Westgate development, road relocation, station relocation and Gloucester Green coach stationrelocation 52

5.9 SIMPLE ASSESSMENT OF THE FEASIBILITIES OF THE OPTIONS CONSIDERED ..................53

6 IMPLICATIONS OF THIS STAGE 4 AIR QUALITY REVIEW ANDASSESSMENT FOR OXFORD...............................................................................54

6.1 CHANGES TO THE AIR QUALITY MANAGEMENT AREA AS A RESULT OF THIS STAGE4 MODELLING ...............................................................................................................................................54

6.2 EFFECTS OF NEW NATIONAL POLICY DEVELOPMENTS..............................................................54

7 THE NEXT STEPS FOR OXFORD .........................................................................567.1 OBTAINING DEFRA APPROVAL..............................................................................................................567.2 LOCAL CONSULTATION ON THIS STAGE 4 ASSESSMENT ............................................................567.3 IMPLEMENTING THE OPTIONS IDENTIFIED TO IMPROVE AIR QUALITY.............................56

8 REFERENCES ........................................................................................................57

9 DEFRA COMPLIANCE CHECKLIST......................................................................58

APPENDICES

Appendix 1 Detailed monitoring data-St EbbesAppendix 2 Detailed traffic flow dataAppendix 3 Model validation - Nitrogen dioxide roadside concentrations

Maps reproduced within this documentAll maps in this document are reproduced from Ordnance Survey material withpermission of Her Majesty’s Stationery Office Crown Copyright. Unauthorisedreproduction infringes Crown copyright and may lead to prosecution or civilproceedings. Oxford City Council Licence number LA078921.

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1 Introduction to this Stage 4 air quality assessment

This section outlines the reason that the Stage 4 air quality review and assessment wascommissioned, and briefly explains what a Stage 4 air quality review and assessment is.

1.1 PURPOSE OF THE STUDY

Oxford City Council has completed a Stage 3 Air Quality Review and Assessment. Theresults of this indicated that exceedences of objectives for nitrogen dioxide (NO2) arelikely at building facades along streets in the Oxford City centre. As a result of this airquality review and assessment, Oxford City Council has declared an air qualitymanagement area.

Oxford City Council now requires further review and assessment of its air quality – aStage 4 review and assessment – as specified under Section 84 of the Environment Act(1995).

1.2 BRIEF EXPLANATION OF A STAGE 4 AIR QUALITY REVIEW AND ASSESSMENT

The 1995 Environment Act places duties on local authorities with regard to local airquality review and, where potential problems are identified, the management of local airquality. The air quality review is designed as a multi-stage process, with progressivelymore complex assessments at each stage.

If a local authority declares an air quality management area, Section 84(1) of theEnvironment Act 1995 requires the local authority to carry out a further assessment ofexisting and likely future air quality in the AQMA. This further assessment is called aStage 4 air quality review and assessment, and is intended to supplement informationthe authority already has.

For each pollutant where there is an exceedence of the air quality, the Stage 4 shouldcalculate:

• how great an improvement is needed; and

• the extent to which different sources contribute to the problem (sourceapportionment).

1.3 OVERVIEW OF APPROACH TAKEN

The general approach taken to this Stage 4 assessment was to:

• Identify the improvement needed in concentrations of nitrogen dioxide at selectedreceptors in the Air Quality Management Area, including the receptors where thegreatest improvements were needed;

• Collect and interpret additional data to support the Stage 4 assessment, includingdetailed traffic flow data around locations where exceedences of the NO2 objectivewere predicted;

• Consider recent continuous monitoring and diffusion tube measurements;

• Identify the contributions of the relevant sources to the exceedences (local traffic,background sources, and other relevant sources);

• Use monitoring data from the NO2 continuous monitor located at the Town Hall andat St Ebbes and diffusion tubes throughout the city to assess the ambient

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concentrations produced by the road traffic and to calibrate the output of the NO2

modelling studies;

• Model the concentrations of NO2 around the selected AQMAs, concentrating on thelocations (receptors) where people might be exposed over the relevant averagingtimes of the air quality objectives;

• Consider relevant scenarios to improve air quality and identify the improvementsin air quality that might be possible for nitrogen dioxide;

• Present the concentrations as contour plots of concentrations and assess theuncertainty in the predicted concentrations;

• Consider any changes that are need to the existing Air Quality Management Areas;

• Consider the feasibilities of implementing the options in a simple way

1.4 RELEVANT DEFRA DOCUMENTATION USED

This report has used the guidance in LAQM.TG4(00), published in May 2000. Referencehas also been made to recent guidance LAQM.TG (03) published in January 2003.

1.5 NUMBERING OF TABLES AND FIGURES

The numbering scheme is not sequential and the figures and tables are numberedaccording to the chapter or section that they relate to.

1.6 POLLUTANTS CONSIDERED IN THIS REPORT

Oxford have only declared an AQMA for nitrogen dioxide and this is the only pollutantconsidered in this report.

1.7 UNITS OF CONCENTRATION USED AND CONVERSIONS TO OTHER UNITS

This report presents concentrations of nitrogen dioxide in units of µg/m3, which isconsistent with units used in the current UK Air Quality Strategy.

To convert concentrations of nitrogen dioxide between µg m-3 and ppb (parts per billion),use the following relationships:

µg m-3 / 1.91 = ppb

1.91 x ppb = µg m-3

1.8 COPYRIGHT OF THE MAPS

All maps in this document are reproduced from Ordnance Survey material withpermission of Her Majesty’s Stationery Office © Crown Copyright. Unauthorisedreproduction infringes Crown copyright and may lead to prosecution or civilproceedings. Oxford City Council Licence number LA078921.

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2 The UK Air Quality Strategy

The Government published its proposals for review of the National Air Quality Strategy inearly 1999 (DETR, 1999). These proposals included revised objectives for many of theregulated pollutants. A key factor in the proposals to revise the objectives was theagreement in June 1998 at the European Union Environment Council of a CommonPosition on Air Quality Daughter Directives (AQDD).

Following consultation on the Review of the National Air Quality Strategy, theGovernment prepared the Air Quality Strategy for England, Scotland, Wales and NorthernIreland for consultation in August 1999. It was published in January 2000 (DETR, 2000).

Table 2.1 Major elements of the Environment Act 1995

Part IV AirQuality

Commentary

Section 80 Obliges the Secretary of State (SoS) to publish a National Air Quality Strategyas soon as possible.

Section 81 Obliges the Environment Agency to take account of the strategy.

Section 82 Requires local authorities, any unitary or district, to review air quality and toassess whether the air quality standards and objectives are being achieved.Areas where standards fall short must be identified.

Section 83 Requires a local authority, for any area where air quality standards are notbeing met, to issue an order designating it an air quality management area(AQMA).

Section 84 Imposes duties on a local authority with respect to AQMAs. The localauthority must carry out further assessments and draw up an action planspecifying the measures to be carried out and the timescale to bring air qualityin the area back within limits.

Section 85 Gives reserve powers to cause assessments to be made in any area and to giveinstructions to a local authority to take specified actions. Authorities have aduty to comply with these instructions.

Section 86 Provides for the role of County Councils to make recommendations to a districton the carrying out of an air quality assessment and the preparation of anaction plan.

Section 87 Provides the SoS with wide ranging powers to make regulations concerning airquality. These include standards and objectives, the conferring of powers andduties, the prohibition and restriction of certain activities or vehicles, theobtaining of information, the levying of fines and penalties, the hearing ofappeals and other criteria. The regulations must be approved by affirmativeresolution of both Houses of Parliament.

Section 88 Provides powers to make guidance which local authorities must have regard to.

This study essentially forms part of the requirements of Section 84 of the Part IV Air Qualityof the Environment Act 1995.

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2.1 OVERVIEW OF THE PRINCIPLES AND MAIN ELEMENTS OF THE AIR QUALITYSTRATEGY

The main elements of the AQS can be summarised as follows:

• The use of a health effects based approach using national air quality standards andobjectives.

• The use of policies by which the objectives can be achieved and which include the inputof important actors such as industry, transportation bodies and local authorities.

• The predetermination of timescales with target dates of 2003, 2004 and 2005 for theachievement of objectives and a commitment to review the Strategy every three years.

It is intended that the AQS will provide a framework for the improvement of air quality thatis both clear and workable. In order to achieve this, the Strategy is based on severalprinciples that include:

• the provision of a statement of the Government’s general aims regarding air quality;• clear and measurable targets;• a balance between local and national action and• a transparent and flexible framework.

Co-operation and participation by different economic and governmental sectors is alsoencouraged within the context of existing and potential future international policycommitments.

2.1.1 National Air Quality StandardsAt the centre of the AQS is the use of national air quality standards to enable air quality tobe measured and assessed. These also provide the means by which objectives andtimescales for the achievement of objectives can be set. Most of the proposed standardshave been based on the available information concerning the health effects resulting fromdifferent ambient concentrations of selected pollutants and are the consensus view ofmedical experts on the Expert Panel on Air Quality Standards (EPAQS). These standardsand associated specific objectives to be achieved between 2003 and 2008 are shown inTable 2.2. The table shows the standards in ppb and µg m-3 with the number ofexceedences that are permitted (where applicable) and the equivalent percentile.

2.1.2 The difference between ‘standards’ and ‘objectives’ in the UK AQSAir quality standards (in the UK AQS) are the concentrations of pollutants in theatmosphere that can broadly be taken to achieve a certain level of environmental quality.The standards are based on assessment of the effects of each pollutant on human healthincluding the effects on sensitive subgroups. The standards have been set at levels toavoid significant risks to health.

The objectives of the UK air quality policy are framed on the basis of the recommendedstandards. The objectives are based on the standards, but take into account feasibility,practicality, and the costs and benefits of fully complying with the standards.

Specific objectives relate either to achieving the full standard or, where use has been madeof a short averaging period, objectives are sometimes expressed in terms of percentilecompliance. The use of percentiles means that a limited number of exceedences of the airquality standard over a particular timescale, usually a year, are permitted. This is toaccount for unusual meteorological conditions or particular events such as November 5th.For example, if an objective is to be complied with at the 99.9th percentile, then 99.9% ofmeasurements at each location must be at or below the level specified.

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Table 2.2 Air Quality Objectives in the Air Quality Regulations (2000) for thepurpose of Local Air Quality Management

Pollutant Concentration limits Averagingperiod

Objective

[number of permittedexceedences a year andequivalent percentile]

(µg m-3) (ppb) (µµµµg m-3) date for objective

Benzene 16.25 5 running annual mean 16.25 by 31.12.2003

1,3-butadiene 2.25 1 running annual mean 2.25 by 31.12.2003

CO 11,600 10,000 running 8-hour mean 11,600 by 31.12.2003

0.5 - annual mean 0.5 by 31.12.2004Pb

0.25 - annual mean 0.25 by 31.12.2008

200 105 1 hour mean 200 by 31.12.2005

[maximum of 18 exceedences a year orequivalent to the 99.8th percentile]

NO2

(see note)

40 21 annual mean 40 by 31.12.2005

50 - 24-hour mean 50 by 31.12.2004

[maximum of 35 exceedences a year or~ equivalent to the 90th percentile]

PM10

(gravimetric)(see note) 40 - annual mean 40 by 31.12.2004

266 100 15 minute mean 266 by 31.12.2005

[maximum of 35 exceedences a year orequivalent to the 99.9th percentile]

SO2

350 132 1 hour mean 350 by 31.12.2004

[maximum of 24 exceedences a year orequivalent to the 99.7th percentile]

125 47 24 hour mean 125 by 31.12.2004

[maximum of 3 exceedences a year orequivalent to the 99th percentile]

Notes

1. Conversions of ppb and ppm to (µg m-3) correct at 20°C and 1013 mb.2. The objectives for nitrogen dioxide are provisional.3. PM10 measured using the European gravimetric transfer standard or equivalent. The

Government and the devolved administrations see this new 24-hour mean objective forparticles as a staging post rather than a final outcome. Work has been set in hand to assessthe prospects of strengthening the new objective.

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2.1.3 Relationship between the UK National Air Quality Standards and EU air quality Limit ValuesAs a member state of the EU, the UK must comply with European Union Directives.

There are three EU ambient air quality directives that the UK has transposed in to UK law.These are:

• 96/62/EC Council Directive of 27 September 1996 on ambient air quality assessment andmanagement. (the Ambient Air Framework Directive)

• 1999/30/EC Council Directive of 22 April 1999 relating to limit values for sulphur dioxide,nitrogen dioxide, oxides of nitrogen, particulate matter and lead in ambient air. (the FirstDaughter Directive)

• 2000/69/EC Directive of the European Parliament and the Council of 16 Nov 2000 relating tolimit values for benzene and carbon monoxide in ambient air. (the Second Daughter Directive)

The first and second daughter directives contain air quality Limit Values for the pollutantsthat are listed in the framework directive. The United Kingdom (i.e. Great Britain andNorthern Ireland) must comply with these Limit Values. The UK air quality strategy shouldallow the UK to comply with the EU Air Quality Daughter Directives, but the UK air qualitystrategy also includes some stricter national objectives for some pollutants, for example,sulphur dioxide.

The Government is ultimately responsibility for achieving the EU limit values. However, itis important that Local Air Quality Management is used as a tool to ensure that thenecessary action is taken at local level to work towards achieving the EU limit values bythe dates specified in those EU Directives.

2.1.4 Changes to the UK National Air Quality StandardsDEFRA issued a consultation document with proposed changes to the UK AQS forbenzene, carbon monoxide and particulate matter (DEFRA, 2001). The proposedchanges were:

For benzene• An objective derived from the long-term policy aim of 3.25 µµµµg/m3 as a running annual

mean recommended by UK EPAQS (Expert Panel on Air Quality Standards). The objective forbenzene included in the 2000 Strategy is 16 µg/m3 as a running annual mean to be achievedby 2003. This is derived from the EPAQS recommended standard. The UK adopted the secondEU Air Quality Daughter Directive (which sets limit values for benzene and carbon monoxide) in2000. This Daughter Directive sets a limit value for benzene of 5 µg/m3 as an annual mean tobe achieved by 2010.

For carbon monoxide• Replacing the existing objective derived from the recently agreed EU limit value. The objective

for carbon monoxide included in the 2000 Strategy is 11.6 mg/m3 as a running 8-hour mean tobe achieved by 2003. This is derived from the UK EPAQS recommended standard. The secondEU Air Quality Daughter Directive sets a limit value for carbon monoxide of 10 mg/m3 as amaximum daily 8-hour mean to be achieved by 2005. DEFRA set a new objective of achievingthe EU limit value by the end of 2003, which is 10 mg/m3 as a maximum daily 8-hourmean to be achieved by 2005.

For particulates new provisional objectives of• for all parts of the UK, except London and Scotland, a 24-hour mean of 50 µµµµg/m3 not to

be exceeded more than 7 time s per year and an annual mean of 20 µµµµg/m3, both to beachieved by the end of 2010;

• for London, a 24-hour mean of 50 µg/m3 not to be exceeded more than 10-14 times per yearand an annual mean of 23-25 µg/m3, both to be achieved by the end of 2010;

• for Scotland, a 24-hour mean of 50 µg/m3 not to be exceeded more than 7 times per year andan annual mean of 18 µg/m3, both to be achieved by the end of 2010.

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These objectives have been included in the Air Quality (England) Amendment Regulationsbut are outside the scope of Stage 4 review and assessment.

2.1.5 Policies in place to allow the objectives for the pollutants in AQS to be achievedThe policy framework to allow these objectives to be achieved is one that that takes a localair quality management approach. This is superimposed upon existing national andinternational regulations in order to effectively tackle local air quality issues as well asissues relating to wider spatial scales. National and EC policies that already exist provide agood basis for progress towards the air quality objectives set for 2003 to 2008. Forexample, the Environmental Protection Act 1990 allows for the monitoring and control ofemissions from industrial processes and various EC Directives have ensured that roadtransport emission and fuel standards are in place. These policies are being developed toinclude more stringent controls. Recent developments in the UK include the announcementby the Environment Agency in January 2000 on controls on emissions of SO2 from coal andoil fired power stations. This system of controls means that by the end of 2005 coal and oilfired power stations will meet the air quality standards set out in the AQS.

Local air quality management provides a strategic role for local authorities in response toparticular air quality problems experienced at a local level. This builds upon current airquality control responsibilities and places an emphasis on bringing together issues relatingto transport, waste, energy and planning in an integrated way. This integrated approachinvolves a number of different aspects. It includes the development of an appropriate localframework that allows air quality issues to be considered alongside other issues relating topolluting activity. It should also enable co-operation with and participation by the generalpublic in addition to other transport, industrial and governmental authorities.

An important part of the Strategy is the requirement for local authorities to carry out airquality reviews and assessments of their area against which current and future compliancewith air quality standards can be measured. Over the longer term, these will also enablethe effects of policies to be studied and therefore help in the development of future policy.The Government has prepared guidance to help local authorities to use the mostappropriate tools and methods for conducting a review and assessment of air quality intheir District. This is part of a package of guidance being prepared to assist with thepracticalities of implementing the AQS. Other guidance covers air quality and land useplanning, air quality and traffic management and the development of local air quality actionplans and strategies.

2.1.6 Timescales to achieve the objectives for the pollutants in AQSIn most local authorities in the UK, objectives will be met for most of the pollutants withinthe timescale of the objectives shown in Table 2.2. It is important to note that theobjectives for NO2 remain provisional. The Government has recognised the problemsassociated with achieving the standard for ozone and this will not therefore be a statutoryrequirement. Ozone is a secondary pollutant and transboundary in nature and it isrecognised that local authorities themselves can exert little influence on concentrationswhen they are the result of regional primary emission patterns.

2.2 AIR QUALITY REVIEWS – THE APPROACHES AND EXPECTED OUTCOMES

A range of Technical Guidance has been issued to enable air quality to be monitored,modelled, reviewed and assessed in an appropriate and consistent fashion. This includesLAQM.TG4(00) May 2000, on ‘Review and Assessment: Pollutant Specific Guidance’ andLAQM.TG(03) on ‘Review and Assessment: Technical Guidance’. This review andassessment has considered the procedures set out in the technical guidance.

The primary objective of undertaking a review of air quality is to identify any areas that areunlikely to meet national air quality objectives and ensure that air quality is considered in

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local authority decision making processes. The complexity and detail required in a reviewdepends on the risk of failing to achieve air quality objectives and it has been proposedtherefore that reviews should be carried out in stages. All the stages of review andassessment may be necessary and every authority is expected to undertake at least a firststage review and assessment of air quality in their authority area. The Stages are brieflydescribed in the following table, Table 2.3.

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Table 2.3 Brief details of Stages in the Air Quality Review and Assessment process

Stage Objective Approach Outcome

First StageReview andAssessment

• Identify all significant pollutantsources within or outside of theauthority’s area.

• Compile and collate a list ofpotentially significant pollutionsources using the assessmentcriteria described in the PollutantSpecific Guidance

• Identify those pollutants wherethere is a risk of exceeding theair quality objectives, and forwhich further investigation isneeded.

• Identify sources requiring furtherinvestigation.

• Decision about whether a Stage 2 Review andAssessment is needed for one or morepollutants. If not, no further review andassessment is necessary.

Second StageReview andAssessment

• Further screening of significantsources to determine whetherthere is a significant risk of the airquality objectives being exceeded.

• Use of screening models ormonitoring methods to assesswhether there is a risk ofexceeding the air qualityobjectives.

• Identify those pollutants wherethere is a risk of exceeding theobjectives, and for which furtherinvestigation is needed.

• The assessment need onlyconsider those locations wherethe highest likely concentrationsare expected, and where publicexposure is relevant.

• Decision about whether a Stage 3 Review andAssessment is needed for one or morepollutants. If, as a result of estimations ofground level concentrations at suitablereceptors, a local authority judges that thereis no significant risk of not achieving an airquality objective, it can be confident that anAir Quality Management Area (AQMA) will notbe required.

• However, if there is doubt that an air qualityobjective will be achieved a third stage reviewshould be conducted.

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Table 2.3 (contd.) Brief details of Stages in the Review and Assessment process

Stage Objective Approach Outcome

Third StageReview andAssessment

• Accurate and detailed assessmentof both current and future airquality. Assess the likelihood ofthe air quality objectives beingexceeded.

• Use of validated modelling andquality-assured monitoringmethods to determine current andfuture pollutant concentrations.

• Identify the geographicalboundary of any exceedences,and description of those areas, ifany, proposed to be designatedas an AQMA.

• The assessment will need toconsider all locations where publicexposure is relevant. For eachpollutant of concern, it may benecessary to construct a detailedemissions inventory and model theextent, location and frequency ofpotential air quality exceedences.

• Determine the location of any necessary AirQuality Management Areas (AQMAs). Once anAQMA has been identified, there are further setsof requirements to be considered.

• A further assessment of air quality in the AQMAis required within 12 months which will enablethe degree to which air quality objectives willnot be met and the sources of pollution thatcontribute to this to be determined. A localauthority must also prepare a written actionplan for achievement of the air qualityobjective. Both air quality reviews and actionplans are to be made publicly available.

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Table 2.3 (contd.) Brief details of Stages in the Review and Assessment process

Stage Objective Approach Outcome

Fourth StageReview andAssessment

(to supportthe ActionPlan)

• Further accurate and detailedassessment of both current andfuture air quality. Shouldconcentrate on areas where theStage 3 assessment indicatedexceedences of the objectives arelikely.

• Use of validated modelling andquality-assured monitoringmethods to determine current andfuture pollutant concentrations.

• Confirm outcome of original AQMA designationand alter if necessary (for example, as a resultof changes in the emission factors used in themodelling)

• Source apportionment in regionswhere there are exceedences.Understand contributions fromtraffic, industrial, domestic andbackground sources.

• Analyse modelling results. • Understand the contributions from the varioussources, and therefore select the source whereaction can be taken to reduce emissions

• Assess a range of scenarios toimprove air quality and reduce oreliminate the risk of air qualityobjectives being exceeded.

• Liaise with stakeholders such asthe Highways Agency, theEnvironment Agency and the localindustry to help define scenarios

• Identify the most likely scenarios to improveair quality and use these in the modelling.Incorporate scenarios into any Action Planproduced.

• Identify the geographicalboundaries of any exceedences inthe scenarios.

• Analyse modelling results. • Incorporate modelling results of the scenariosinto any Action Plan produced. Consider howto implement any Action Plan to improve airquality.

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Local authorities are expected to have completed review and assessment of air quality byDecember 2000. A further review will also need to be completed for the purposes of theAct before the target date of 2003.

2.3 LOCATIONS THAT THE REVIEW AND ASSESSMENT MUST CONCENTRATE ON

For the purpose of review and assessment, the authority should focus their work onlocations where members of the public are likely to be exposed over the averaging periodof the objective. Table 2.4 summarises the locations where the objectives should andshould not apply.

Table 2.4 Typical locations where the objectives should and should not apply

AveragingPeriod

Pollutants Objectives shouldapply at …

Objectives shouldnot generally applyat …

Annual mean • 1,3 Butadiene• Benzene• Lead• Nitrogen dioxide• Particulate Matter

(PM10)

• All backgroundlocations wheremembers of thepublic might beregularly exposed.

• Building facadesof offices or otherplaces of workwhere members ofthe public do nothave regularaccess.

• Building facadesof residentialproperties,schools, hospitals,libraries etc.

• Gardens ofresidentialproperties.

• Kerbside sites (asopposed tolocations at thebuilding facade),or any otherlocation wherepublic exposure isexpected to beshort term

24 hour meanand8-hour mean

• Carbon monoxide• Particulate Matter

(PM10)• Sulphur dioxide

• All locationswhere the annualmean objectivewould apply.

• Kerbside sites (asopposed tolocations at thebuilding facade),or any otherlocation wherepublic exposure isexpected to beshort term.

• Gardens ofresidentialproperties.

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Table 2.4 (contd.) Typical locations where the objectives should and should not apply

AveragingPeriod

Pollutants Objectives shouldapply at …

Objectives shouldgenerally not applyat …

1 hour mean • Nitrogen dioxide• Sulphur dioxide

• All locationswhere the annualmean and 24 and8-hour meanobjectives apply.

• Kerbside siteswhere the publicwould not beexpected to haveregular access.

• Kerbside sites(e.g. pavementsof busy shoppingstreets).

• Those parts of carparks and railwaystations etc. thatare not fullyenclosed.

• Any outdoorlocations to whichthe public mightreasonablyexpected to haveaccess.

15 minutemean

• Sulphur dioxide • All locationswhere members ofthe public mightreasonably beexposed for aperiod of 15minutes or longer.

It is unnecessary to consider exceedences of the objectives at any location where publicexposure over the relevant averaging period would be unrealistic, and the locationsshould represent non-occupational exposure.

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3 Stage 4 Air Quality Review and Assessment and Action Planning

This section contains information about Stage 4 Air Quality Review and Assessments andAction Plans. It explains the relationships between the Stage 4 and Action Plans, whateach document should contain, and the timescales for producing the documents.

3.1 THE RELATIONSHIPS BETWEEN A STAGE 4 AIR QUALITY REVIEW AND ASSESSMENTAND AN ACTION PLAN

If a local authority declares an air quality management area, Section 84(1) of theEnvironment Act 1995 requires that local authority to carry out a further assessment ofexisting and likely future air quality in the AQMA. This further assessment is called aStage 4 air quality review and assessment, and is intended to supplement informationthe authority already has. It is a duty of the LA to complete this Stage 4 air qualityreview and assessment.

For each pollutant where there is an exceedence of the air quality, the Stage 4 shouldcalculate:

• how great an improvement is needed; and

• the extent to which different sources contribute to the problem (sourceapportionment of traffic, industrial, domestic and background – if appropriate).

This should give a clear picture of the sources that authorities can control or influence. Itshould ensure that Action Plans strike a balance between the contribution from localauthorities and the contribution that must come from other sectors. It should allow themto target their responses more effectively and ensure that the relative contributions ofindustry, transport and other sectors are cost effective and proportionate. It shouldinclude, in particular, an estimate of the costs and feasibility of different abatementoptions to allow for the development of proportionate and effective Action Plans(although this information could be included within the Action Plan, rather than theStage 4). Further liaison with other agencies (including, in particular, the EnvironmentAgency and the Highways Agency) is likely to be essential.

Essentially, producing the Stage 4 air quality review and assessment and the Action Planare activities that the LA can completed in parallel, rather than sequentially.

3.2 DEFRA GUIDANCE ON STAGE 4 AIR QUALITY REVIEW AND ASSESSMENT

DEFRA have issued guidance on what they expect in a Stage 4. This expands on theinformation that is available in LAQM.G1(00) - Framework for review and assessment ofair quality.

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Essentially, the Stage 4 provides the technical justification for the measures an authorityincludes in its Action Plan. DEFRA expect that the Stage 4 will allow Local Authorities:

• To calculate more accurately how much of an improvement in air quality is neededto deliver the air quality objectives within the AQMA

• To refine their knowledge of the sources of pollution so that air quality Action Planscan be properly targeted

• To take account of national policy developments that may come to light after theAQMA declaration (the revision of the vehicle emission factors is an example of thiskind of policy development)

• To take account of local policy developments, for example, new transport schemesin the vicinity of the AQMA or of any new major housing or commercialdevelopments

• To carry out more intensive monitoring in the problem areas to confirm earlierfindings

• To corroborate other assumptions on which the designation of the AQMA wasbased and to check that the original designation is still valid, and does not needamending

• To respond to comments made by statutory consultees (if there were any relevantcomments made)

3.3 ACTION PLANS

Local authorities are required to prepare a written Action Plan for each AQMA setting outthe actions they intend to take in pursuit of the air quality objectives. This has to includea timetable for implementing the plan.

The Action Plan should contain the scenarios that have been modelled in the Stage 4review and assessment. It should contain a summary of the air quality improvementsthat might be possible for each of the scenarios identified. The Stage 4 provides thetechnical justification for the measures an authority includes in its Action Plan.

The Action Plan should also contain simple estimates of the costs and feasibilities ofimplementing those scenarios. The Action Plan may also consider the non-healthbenefits of implementing scenarios in the Action Plan, for example, reductions in roadtraffic accident deaths as a result of road improvements that also reduce vehicleemissions.

The LA can then identify which scenario(s) offer the most cost-effective or cost-beneficialway of improving air quality.

3.4 STAGE 4 AND ACTION PLAN TIMESCALES

The Environment Act does not set any deadline for completing action plans, but theGovernment expects authorities to begin preparing them as soon as they havedesignated an AQMA, and in parallel with their further assessment of air quality requiredunder section 84(1) of the Environment Act. Authorities should not wait until they havecompleted their further assessment of air quality before beginning their Action Plans.They should aim to consult on their draft AQMA Action Plans within 9-12 months ofdesignation, and should have AQMA Action Plans in place within 12-18 months ofdesignation.

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Local authorities are required under section 84(2)(a) of the Environment Act to report onthe further assessment of air quality (i.e. the Stage 4 Air Quality Review andAssessment) within 12 months of designating the Air Quality Management Area.Oxford City Council plan to submit their Action Plan in autumn 2003.

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4 Information used to support this assessment

This section lists the key information used in this review and assessment.

4.1 MAPS AND DISTANCES OF RECEPTORS FROM ROADS

Oxford City Council provided detailed OS landline data of the City Centre including theroads in the AQMA. Individual buildings or groups of buildings (receptors) were identifiedfrom the electronic OS Landline maps of the areas and the distances of these receptorsfrom the road determined from the maps.

All maps in this document are reproduced from Ordnance Survey material withpermission of Her Majesty’s Stationery Office Crown Copyright. Unauthorisedreproduction infringes Crown copyright and may lead to prosecution or civilproceedings. Oxford City Council Licence LA078921 .

4.2 ROAD TRAFFIC DATA

Traffic flows on the roads throughout Oxford City centre were modelled by OxfordshireCounty Council using their Saturn traffic model. The model provided estimates of trafficflow, traffic speed and fraction of heavy duty vehicles on each road link. The estimates oftraffic speeds provided by the Saturn traffic model were reviewed, with particularattention paid to road junctions. Separate SATURN model runs were carried out for theyears 2000, 2001, 2002 and 2005 to take account of the anticipated changes in traffic inOxford City centre. Detailed traffic data used in the assessment is presented in AppendixA.

Oxfordshire County Council provided details of typical daily and weekly variations intraffic flow derived from traffic count data.

4.3 AMBIENT MONITORING

Nitrogen dioxide concentrations were monitored at many locations throughout OxfordCity Centre:

• The St Ebbes continuous monitoring station (grid reference 51150, 05400) is ina background location away from major roads in the grounds of a school a fewhundred metres south of the city centre. The monitoring device operates usingthe ozone chemiluminesence technique.

• The St Aldates monitoring station (grid reference 51350, 06150) is in thebasement of the Town Hall in St Aldates, a two way street close to the centre ofOxford. Traffic along St Aldates is limited to buses and access traffic, but thestreet is often congested close to bus stops near to the monitoring station. Themanifold intake is approximately 2 m from the kerbside and 3.5 m aboveground. The location of the monitoring station is representative of many of theareas of concern in Oxford city centre that are close to congested roads withheavy bus traffic. The monitoring device operates using the ozonechemiluminesence technique.

• Diffusion tubes are installed at 59 locations throughout the centre of Oxford.

Ozone chemiluminescence is the reference method specified by the EC NO2 Directives.Calibration methods employed included primary calibration by permeation tube,gravimetric cylinder and static dilution and transfer calibration by cylinder audit during

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fortnightly site visit. The expected accuracy of the method for nitrogen dioxide is ±10-11% with a precision of ±3.5 ppb.

The St Aldates Town Hall continuous monitoring site forms part of the UK AutomaticUrban Network and the data is ratified and collated according to national standards forthe network. Data reports for the St Ebbes site are provided in Appendix 1.Diffusion tubes are collocated at the continuous monitoring stations in order to allow anassessment to be made of the bias in the diffusion tube measurements. The diffusiontubes were provided and analysed by Rotherham Metropolitan Borough Councillaboratory.

4.4 EMISSION FACTORS USED IN THIS REVIEW AND ASSESSMENT

The vehicle emission factors used for national mapping have recently been revised byDEFRA3. The most recent emission factors have been used in this Stage 4.

In Oxford City Council’s Stage 3, older emission factors were used. Using the newerfactors will result in some differences in the modelled results between the Stage 3 andthe Stage 4.

4.5 LIAISON WITH OTHER ORGANISATIONS

Oxford City Council have consulted extensively with Oxfordshire County Council indeveloping options for their Action Plan.

3 The new set of emission factors on the NAEI website(www.naei.org.uk/emissions/index.php) approved by DEFRA and DTLR for use in emissionsand air quality modelling, following consultation of the TRL Report "Exhaust EmissionFactors 2001: Database and Emission Factors" by TJ Barlow, AJ Hickman and P Boulter,TRL, September 2001

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5 Stage 4 Review and Assessment for Nitrogen Dioxide

This section summarises

• the work that was done at Stage 3 and the areas of exceedence of the air qualityobjectives for nitrogen dioxide;

• monitoring that was completed for the Stage 3 Air Quality Review and Assessment;

• the additional monitoring that has been done after Stage 3 to confirm the predictedconcentrations in the Air Quality Management Area or to more generally assessconcentrations in Oxford;

• the Stage 4 modelling, which includes predictions of concentrations of nitrogendioxide for a range of Action Plan scenarios to improve air quality.

5.1 STANDARDS AND OBJECTIVES FOR NITROGEN DIOXIDE

In June 1998, the Common Position on Air Quality Daughter Directives (AQDD) agreed atEnvironment Council included the following objectives to be achieved by 31 December2005 for nitrogen dioxide:

• An annual average concentration of 40 µg m-3 (21 ppb);

• 200 µg m-3 (100 ppb) as an hourly average with a maximum of 18 exceedences in ayear.

The Air Quality Strategy for England, Scotland, Wales and Northern Ireland (DETR, 2000)and the Air Quality Regulations (2000) adopted the Directive limits as objectives.

Modelling studies suggest that in general achieving the annual mean of 40 µg m-3 is moredemanding than achieving hourly objective. If the annual mean is achieved, themodelling suggests the hourly objectives will also be achieved.

5.2 KEY FINDINGS OF THE STAGE 3 REVIEW AND ASSESSMENT

The Stage 2 air quality assessment for Oxford identified areas that required furtherassessment of nitrogen dioxide. A Stage 3 Review and Assessment was completed,which involved detailed dispersion modelling around selected hotspots to predict areas ofexceedence of the nitrogen dioxide objectives (netcen, 2000).

The detailed dispersion modelling results show that it was probable or likely (i.e. morelikely than not) that the annual average objective would not be met at building facadeson the following city centre streets:

St GilesMagdalen StreetBeaumont Street, east of Gloucester StreetGeorge StreetGloucester Green bus stationWorcester StreetPark End StreetHythe Bridge StreetHollybush Row, north of St Thomas StreetSpeedwell StreetSt Aldates, north of Thames Street

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High StreetSt Clements StreetOld Greyfriar Street

The dispersion modelling showed that, in general, the expected area of exceedence waslimited to the buildings with facades on these streets: the area of expected exceedencedid not extend further back from the roads.

Diffusion tube measurements also indicated that the objective was not likely to be meton:

New Road and Longwall Street.

Consideration was given to the possibility of designating Air Quality Management Areasat the locations assessed. Factors taken into account included:

• the likelihood that members of the public will be exposed over the relevant averagingtime;

• the likelihood that the objective will be met;• the physical boundaries that might be used to define Air Quality Management Areas

There are people resident on many of the streets and so it is to be expected that they willbe exposed over the averaging time of the objective.

For convenience and ease of description, it was desirable to declare a single city centreAQMA.

5.3 AREA DECLARED BY OXFORD AS AN AIR QUALITY MANAGEMENT AREA

The following area was declared by Oxford City Council as an AQMA:

Buildings with facades on the following roads:

St Giles, south of Pusey StreetMagdalen StreetBeaumont StreetGeorge StreetGloucester Green bus stationWorcester StreetPark End StreetHythe Bridge StreetHollybush Row, north of St Thomas StreetSpeedwell StreetSt Aldates Street, north of Thames StreetHigh StreetSt Clements StreetOld Greyfriar StreetLongwall StreetNew RoadCastle Street

The AQMA area is shown in Fig. 5.1.

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Fig. 5.1: Roads defining City Centre Air Quality Management AreaBased upon the Ordnance Survey mapping with the permission of the Controller of Her majesty’s Stationery Office Crown copyright. Unauthorised reproductioninfringes Crown copyright and may lead to prosecution or civil proceedings. Oxford City Council LA078921

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5.4 MONITORING

5.4.1 Monitoring data included in the Stage 3 report

Table 5.1 summarises the nitrogen dioxide concentrations measured at the continuousmonitors at the Town Hall and St Ebbes during 1998 and 1999 and reported at Stage 3.

Table 5.1: Summary of continuous nitrogen dioxide measurements at St Aldates TownHall and St Ebbes included in the Stage 3 report

St Aldates, Town Hall St Ebbes1998 1999 1998 1999

Average, µg m-3 52 56 22 22

Maximum hourly, µgm-3

164 229 103 101

99.8 th %ile hourly, µgm-3

143 178 78 84

Data capture, % 71.1 98.7 92.9 92.8

Table 5.2 shows diffusion tube measurements include in the Stage 3 report. The OxfordTransport Strategy was implemented during June 1999: Table 5.2 shows averageconcentrations pre OTS and post OTS in addition to the annual average concentration.The measured concentrations were corrected for measurement bias determined on thebasis of diffusion tube measurements at a site collocated with the Town Hall continuousmonitor.

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Table 5.2:Diffusion tube measurements included in the Stage 3 report: averageconcentrations, 1999Site Concentration, µg m-3 *Corrected concentration, µg m-3 Number of

measurementsAnnual PreOTS PostOTS Annual PreOTS PostOTS

Folly Bridge 50.7 52.0 49.7 43 44.3 42.0 12Shirelake Close 33.4 38.8 30.4 25.7 31.1 22.7 11Thames St 49.4 56.7 46.3 41.7 49.0 38.6 10Thames/Trinity St 30.9 31.8 30.2 23.2 24.1 22.5 12Thames/Oxpens 45.1 46.2 44.3 37.4 38.5 36.6 12Thames/Sadler Wk 30.1 32.4 28.4 22.4 24.7 20.7 12Norfolk St 38.5 48.8 31.7 30.8 41.1 24.0 10Paradise Sq 35.4 32.8 37.1 27.7 25.1 29.4 10Pike Terr (36 Falkner St) 50.1 50.4 49.9 42.4 42.7 42.2 12Speedwell/Littlegate 55.6 54.8 56.5 47.9 47.1 48.8 9Butterwyke / Thames 41.1 36.3 43.9 33.4 28.6 36.2 11Floyd's Row 48.9 50.6 47.6 41.2 42.9 39.9 11Osney Ln/Woodbine Pl 37.6 37.4 37.7 29.9 29.7 30.0 12Hollybush / Osney Ln 41.2 41.6 40.9 33.5 33.9 33.2 12Beckett St/Pk End St 43.9 45.0 43.1 36.2 37.3 35.4 9Park End/Rewley Rd 63.0 67.0 59.6 55.3 59.3 51.9 11Park End St 59.5 59.8 59.3 51.8 52.1 51.6 11New Rd 65.4 63.4 67.1 57.7 55.7 59.4 11Worcester St 69.2 68.4 69.8 61.5 60.7 62.1 12Walton St 40.0 40.8 39.5 32.3 33.1 31.8 11Gloucester St 45.6 45.6 45.6 37.9 37.9 37.9 12Beaumont Bldgs 33.1 37.6 29.9 25.4 29.9 22.2 12Beaumont St 59.0 63.3 56.6 51.3 55.6 48.9 11Pusey St /St Giles 39.7 40.8 38.8 32 33.1 31.1 11St Giles Ashmolean 79.4 84.4 75.8 71.7 76.7 68.1 12Keble Rd 53.0 57.8 49.5 45.3 50.1 41.8 12Univ Sci Lib-Parks Rd 47.8 47.0 48.4 40.1 39.3 40.7 12Parks Rd 43.2 46.4 40.9 35.5 38.7 33.2 12Mansfield Rd 36.7 38.8 35.2 29 31.1 27.5 12Manor Rd/St Cross Rd 38.6 40.6 37.1 30.9 32.9 29.4 12Longwall St 78.0 81.4 75.6 70.3 73.7 67.9 12York Place 48.8 49.6 48.3 41.1 41.9 40.6 12Iffley Rd/Plain 44.4 44.2 44.5 36.7 36.5 36.8 12Magdalen Bridge 45.6 48.2 43.5 37.9 40.5 35.8 11High St 81.4 89.0 76.0 73.7 81.3 68.3 12Broad St 44.8 51.3 40.5 37.1 43.6 32.8 10Cornmarket 58.2 73.0 47.6 50.5 65.3 39.9 12Lyndworth Cl 38.7 38.2 39.1 31 30.5 31.4 12St Aldates Th 63.0 61.5 63.9 55.3 53.8 56.2 11Blue Boar St 45.2 49.0 42.6 37.5 41.3 34.9 10Worcester Coll 28.9 29.6 28.4 21.2 21.9 20.7 12Univ S Parks Rd 45.2 47.4 43.6 37.5 39.7 35.9 12George St 85.8 74.0 95.2 78.1 66.3 87.5 9St Clements St 82.6 88.0 78.8 74.9 80.3 71.1 12Queen St 88.5 92.6 85.6 80.8 84.9 77.9 12George St/Magdalen St 85.3 84.8 85.7 77.6 77.1 78.0 11Hythe Bridge St 57.6 57.8 57.5 49.9 50.1 49.8 11Botley Road 52.0 50.6 53.1 44.3 42.9 45.4 12Duke St 31.6 31.6 31.6 23.9 23.9 23.9 11Binsey 19.3 20.4 18.5 11.6 12.7 10.8 12Green Rd Roundabout 66.5 65.2 67.4 58.8 57.5 59.7 12Lenthall Rd Allotments 20.1 21.6 18.9 12.4 13.9 11.2 11Bonn Sq 56.1 53.8 57.8 48.4 46.1 50.1 12St Aldate's 83.2 90.3 77.8 75.5 82.6 70.1 7HIGH(Rpm) 84.9 93.5 82.0 77.2 85.8 74.3 8STATION(Busstop) 80.5 72.8 2

*7.7 µg m-3 subtracted to take account of bias in diffusion tube measurements.

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5.4.2 Additional monitoring after the Stage 3 Review and Assessment was completed

The continuous monitors at St Aldates Town Hall and St Ebbes have continued to operatesince the Stage 3 report. Table 5.3 shows the measured concentrations of nitrogendioxide and oxides of nitrogen at the Town Hall and St Ebbes sites.

The diffusion tube survey has also continued, with additional sites at St Ebbes (collocatedwith the continuous monitor) and at Abingdon Road, Boundary Brook Road and EastOxford. Table 5.4 shows the measured concentrations at the diffusion tube sites. It alsoshows the diffusion tube measurements corrected for bias based on bias adjustmentfactors derived from collocated tubes at the Town Hall and St Ebbes continuousmonitoring sites.

Table 5.3: Nitrogen dioxide concentrations at continuous monitoring sites in Oxford citycentre

Concentrations, µg m-3

2000 2001 2002Town Hall Nitrogen dioxide annual mean 60.3 59.6 59.5

Nitrogen dioxide, 99.8%ilehourly means

172 162 167

Oxides of nitrogen, annualmean

184 184 185

Oxides of nitrogen, 99.8%ilehourly means

896 884 790

Data >99% >99% >99%St Ebbes Nitrogen dioxide annual mean 19.6 22.5 21.4

Nitrogen dioxide, 99.8%ilehourly means

76.4 74.4 75.5

Oxides of nitrogen, annualmean

36.5 44.1 38.5

Oxides of nitrogen, 99.8%ilehourly means

376 456 345

Data 91% 86% 94%

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Table 5.4: Diffusion tube measurements since the Stage 3 report: averageconcentrations, 2000-2002

Nitrogen dioxide concentration, µg m-3

Uncorrected Corrected

Town Hall Factor St Ebbes factor

2000 2001 2002 2000 2001 2002 2000 2001 2002

Abingdon Rd / Weirs Ln 49 49 42

BEAUMONT BLDGS 33 34 30 34 34 30 24 26 25

BEAUMONT ST 59 62 54 60 61 54 42 48 46

BECKETT ST/PK END ST 39 40 39 40 39 39 28 31 33

BINSEY 18 20 17 18 19 16 12 15 14

BLUE BOAR ST 39 42 40 40 42 40 27 33 34

BONN SQ 52 58 54 53 57 53 37 44 46

BOTLEY ROAD 47 45 43 48 44 43 33 35 36

Boundary Brook Rd 45 45 38

BROAD ST 39 40 37 40 40 37 28 31 31

BUTTERWYKE/THAMES 40 46 39 41 45 39 29 35 33

CORNMARKET ST 49 49 44 50 48 44 35 38 38

DUKE ST 33 36 32 34 35 32 24 28 27

East Oxford 32 36 31 33 35 30 23 28 26

FLOYD'S ROW 51 53 47 53 52 47 37 40 40

FOLLY BRIDGE 44 47 42 45 46 42 32 36 36

GEORGE ST 86 85 80 88 84 79 61 65 68

GEORGE ST/MAGDALENST

78 70 69 80 69 69 55 54 59

GLOUCESTER ST 42 49 42 43 48 42 30 38 36

GREEN RDROUNDABOUT

66 67 62 67 66 61 47 51 52

HIGH ST 68 70 76 70 69 76 49 54 65

HIGH St (RPM) 78 78 79 80 77 79 56 60 68

HOLLYBUSH / OSNEY L 42 44 39 43 43 39 30 34 33

HYTHE BRIDGE ST 55 55 53 56 54 53 39 42 45

IFFLEY RD/PLAIN 42 42 40 43 42 40 30 32 34

KEBLE RD 45 48 43 46 47 43 32 37 37

LENTHALL RDALLOTMENTS

22 28 23 22 27 23 15 21 20

LONGWALL ST 67 62 61 68 61 61 47 48 52

LYNDWORTH CL 38 37 32 39 36 32 27 28 27

MAGDALEN BRIDGE 41 44 38 42 43 38 29 34 33

MANOR RD/ST CROSSRD

36 35 32 37 35 32 26 27 27

MANSFIELD RD 35 35 32 36 34 32 25 27 27

NEW RD 64 73 69 65 72 69 45 56 59

NORFOLK ST 34 39 32 34 39 32 24 30 28

OSNEY LN/WOODBINEPL

32 36 31 33 36 31 23 28 27

PARADISE SQ 29 32 25 30 31 25 21 24 21

PARK END ST 55 62 59 57 61 58 39 48 50

PARK END/REWLEY RD 59 62 54 60 61 54 42 48 46

PARKS RD 38 41 37 39 40 37 27 31 32

PIKE TERR 47 47 44 48 46 44 33 36 37

PUSEY ST /ST GILES 40 42 40 41 41 40 29 32 34

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Nitrogen dioxide concentration, µg m-3

Uncorrected Corrected

Town Hall Factor St Ebbes factor

2000 2001 2002 2000 2001 2002 2000 2001 2002

QUEEN ST 84 77 83 86 75 83 60 59 71

SHIRELAKE CLOSE 33 37 30 34 37 30 24 29 26

SPEEDWELL/LITTLEGATE 51 52 48 52 52 48 36 40 41

ST ALDATES 59 61 60 60 60 60 42 47 51

St CLEMENTS ST 74 72 74 76 71 74 53 55 63

St Ebbe's 28 29 25 28 29 25 20 23 21

ST GILES ASHMOLEAN 72 69 65 73 68 65 51 53 55

STATION(busstop) 72 79 73 73 78 72 51 61 62

THAMES ST 47 49 41 48 48 41 33 37 35

THAMES/OXPENS 39 45 37 40 44 37 28 34 32

THAMES/SADLER WK 27 30 26 28 30 26 20 23 22

THAMES/TRINITY ST 29 31 29 30 31 29 21 24 25

UNIV S PARKS Rd 41 43 39 42 42 39 30 33 33

UNIV SCI LIB-PARKS RD 43 45 42 44 44 42 31 34 36

WALTON ST 34 38 34 35 38 34 24 29 29

WORCESTER COLL 30 32 29 31 31 29 22 25 24

WORCESTER ST 64 66 62 65 65 62 45 51 53

YORK PLACE 57 46 42 58 45 42 41 35 36

Continuous monitoring

Town Hall, St Aldates 60 60 60

St Ebbes 20 23 21

Bias adjustment factor

Town Hall, St Aldates 0.98 1.02 1.00

St Ebbes 1.40 1.30 1.17

5.4.3 Changes in nitrogen dioxide concentrations since the Stage 3 review

Comparison of Table 5.1 for 1999 with Table 5.3 for 2000-2002 indicates that nitrogendioxide concentrations at the Town Hall continuous monitoring site have increasedslightly since the Stage 3 Review and Assessment was carried out. The changes at theTown Hall site may have arisen because of changes to the layout of bus stops in thevicinity of the monitoring station.

Similar comparison of nitrogen dioxide concentrations at the St Ebbes site indicates thatthe nitrogen dioxide concentration at this background site has not changed since theStage 3 review and Assessment.

Fig. 5.2 shows the concentration at diffusion tube sites for 2002 plotted against theconcentration for 1999. Both sets of diffusion tube measurements have been correctedfor diffusion tube bias for the appropriate year on the basis of the collocated tubes at theTown Hall. A 1:1 equivalence line is also shown for comparison. Fig.5.2 indicates thatthere has not been any general improvement in nitrogen dioxide concentrations in Oxfordcity centre since the Stage 3 review and Assessment, although there my have been somechanges at individual sites. [Note that the apparent deterioration in air quality at siteswhere the nitrogen dioxide concentration is less than 30 µg m-3 may be associated withdifferent methods for allowing for diffusion tube bias.]

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Fig. 5.2: Comparison of diffusion tube measurements 1999 and 2002

5.4.4 Factors used to predict future diffusion tube concentrations from current concentrationsThe DEFRA Review and Assessment: Technical Guidance. LAQM.TG(03) January 2003provides factors to project forward concentrations at background and roadside locationsbased on the concentrations measured in recent years. The following factors have beenused in this assessment for nitrogen dioxide, depending on the location of the diffusiontube:

Background• 2002 to 2005 0.93Kerbside• 2002 to 2005 0.92

Table 5.5 shows the forecast for 2005 nitrogen dioxide concentrations based on the 2002diffusion tube measurements, adjusted for bias based on the comparison of collocatedtubes with continuous monitoring data at Town Hall and St Ebbes.

0

10

20

30

40

50

60

70

80

90

0 10 20 30 40 50 60 70 80 90Nitrogen dioxide concentration, 1999, ug/m3

Nitr

ogen

dio

xide

con

cent

ratio

n, 2

002,

ug/

m3

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Table 5.5: Forecast nitrogen dioxide concentrations 2005 at diffusion tube sites

Site Concentration, µg m-3

Town Hall biasadjustment

St Ebbes biasadjustment

Abingdon Rd / Weirs Ln 45 39BEAUMONT BLDGS 28 23BEAUMONT ST 50 42BECKETT ST/PK END ST 36 30BINSEY 15 13BLUE BOAR ST 37 31BONN SQ 49 42BOTLEY ROAD 40 33Boundary Brook Rd 41 35BROAD ST 34 29BUTTERWYKE/THAMES 36 30CORNMARKET ST 40 35DUKE ST 29 25East Oxford 28 24FLOYD'S ROW 43 37FOLLY BRIDGE 39 33GEORGE ST 73 63GEORGE ST/MAGDALEN ST 63 54GLOUCESTER ST 39 33GREEN RD ROUNDABOUT 56 48HIGH ST 70 60HIGH St (RPM) 73 63HOLLYBUSH / OSNEY L 36 30HYTHE BRIDGE ST 49 41IFFLEY RD/PLAIN 37 31KEBLE RD 40 34LENTHALL RD ALLOTMENTS 21 18LONGWALL ST 56 48LYNDWORTH CL 29 25MAGDALEN BRIDGE 35 30MANOR RD/ST CROSS RD 29 25MANSFIELD RD 29 25NEW RD 63 54NORFOLK ST 29 26OSNEY LN/WOODBINE PL 29 25PARADISE SQ 23 19PARK END ST 53 46PARK END/REWLEY RD 50 42PARKS RD 34 29PIKE TERR 40 34PUSEY ST /ST GILES 37 31QUEEN ST 76 65SHIRELAKE CLOSE 28 24SPEEDWELL/LITTLEGATE 44 38ST ALDATES 55 47St CLEMENTS ST 68 58St Ebbe's 23 19ST GILES ASHMOLEAN 60 51STATION(busstop) 66 57THAMES ST 38 32THAMES/OXPENS 34 29THAMES/SADLER WK 24 20THAMES/TRINITY ST 27 23UNIV S PARKS Rd 36 30UNIV SCI LIB-PARKS RD 39 33WALTON ST 31 27WORCESTER COLL 27 22WORCESTER ST 57 49YORK PLACE 39 33

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5.4.5 Comparison of the monitoring results with the relevant air quality objectives

Nitrogen dioxide measurements at the continuous monitoring site at the Town Hall (Table5.3) show that the annual mean objective of 40 µg m-3 for 2005 is currently exceeded.Projecting the 2002 measurement forward to 2005 indicates that the objective will not bemet.

Measurements at the St Ebbes background site show that the objective is currently met:it is likely that the objective will be met in 2005.

Forecasted nitrogen dioxide concentrations based on diffusion tube measurementscorrected on the basis of the comparison of diffusion tube measurements with acollocated continuous monitor at St Ebbes for 2002, shown in Table 5.5 indicate that theobjective will not be met at a number of sites in the diffusion tube survey. These sitesare:

Beaumont StreetBonn SquareGeorge StreetGeorge Street/Magdalen StreetGreen Road RoundaboutHigh StreetHigh Street RPMHythe Bridge StreetLongwall StreetNew RoadPark End StreetPark End/Rewley RoadQueen StreetSt AldatesSt Clements StreetSt Giles/AshmoleanStation bus stop

In addition, diffusion tubes corrected on the basis of the collocated tubes at Town Hallindicate that the following sites may also fail to meet the objective in 2005.

Abingdon Road/Weirs LaneBotley RoadBoundary Brook RoadCornmarket StreetFloyd’s RowKeble RoadPike TerraceSpeedwell/Littlegate

Of these sites, Abingdon Road, Boundary Brook Road and the Green Road Roundaboutare some distance outside the AQMA. They will not be considered further as part of thisStage 4 review, but should be given further consideration during the Screening andUpdating Assessment.

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The diffusion tube at St Clements is sandwiched between two road signs on a lamppostfor security reasons: it is unlikely to provide a reliable measure of nitrogen dioxideconcentrations in the surrounding area.

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5.5 OVERVIEW OF THE AIR QUALITY MODELLING FOR THIS STAGE 4 ASSESSMENT

5.5.1 Summary of the model used in this Stage 4 assessment

The dispersion model ADMS-Urban was used to predict nitrogen dioxide concentrations atroadside locations in Oxford. ADMS-Urban is a PC-based model that includes an up-to-date representation of the atmospheric processes that contribute to pollutant dispersion.It is described in some detail in a User Manual [CERC, 2000]. The model was used topredict the local contribution to nitrogen dioxide concentrations from roads.

The model contains a detailed road model taking account of emissions from roads in theareas of concern. Many of the streets in the city centre are relatively narrow and aresurrounded by high buildings that hinder the ventilation of the street causing elevatedpollutant concentrations. ADMS-Urban contains a street canyon model that takes accountof many of the effects of the buildings.

Each of the road links in the vicinity of the areas of interest was split into a number ofshort sections taking account of the changing conditions along the length of each roadlink. The length and width of each section of road were determined from detailedOrdnance Survey maps using the ArcView Geographical Information System.

A survey of building heights forming street canyons in Oxford city centre was carried outand the data included within the model input.

Rates of emission of oxides of nitrogen were calculated for each section of road based onOxfordshire County Council’s Saturn traffic model using the most recent emission factorspublished by the National Atmospheric Emissions Inventory on behalf of DEFRA.

The estimates of traffic speeds provided by the Saturn traffic model were reviewed, withparticular attention paid to road junctions. Separate road sections were included withinthe model where there was evidence of slow traffic and traffic queuing at road junctions.

Wind speed and direction data for each hour of 2000 were obtained from the air qualitymonitoring station at St Ebbes. The monitoring station is in open ground to the southeast of the city. The wind speed and direction data were supplemented with cloud coverdata from Brize Norton for each hour.

It was assumed that a surface roughness of 1.5 m was representative of the city centrearea. The surface roughness at the meteorological site at St Ebbes was assumed to be1.0 m.

The meteorological conditions over Oxford are affected by heat emissions from buildingsand vehicles. This “urban heat island” effect reduces the frequency and severity of thestable atmospheric conditions that often lead to high pollutant concentrations. In order totake this into account the Monin-Obukhov length (a parameter used to characteriseatmospheric stability in the model) has been assigned a lower limit of 30 m typical ofmixed urban/industrial areas.

The background concentration of oxides of nitrogen and nitrogen dioxide for each hour ofthe modelled year was determined from the measurements at the St Ebbes site.Conversion of oxides of nitrogen to nitrogen dioxide was modelled using the Derwent-Middleton equation.

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5.5.2 Validation and verification of the model

In simple terms, model validation is where the model is tested at a range of locationsand is judged suitable to use for a given application. The ADMS Urban model used in thisassessment has been validated, and used in numerous air quality review andassessments. Details of the model validation are given in Appendix 2.

Verification of the model involves comparison of the modelled results with any localmonitoring data at relevant locations. Relevant data includes measurements from thecontinuous monitoring stations at the Town Hall and at St Ebbes and the diffusion tubemeasurements obtained throughout the city centre. In order to make use of the verifiedmodel it is essential that the measurements used for verification are representative ofthe area of model application. Furthermore, it is essential that the rates of emission ofpollutants and the dispersion conditions in the area of the measurement site are wellcharacterised and properly represented in the model.

Oxford city centre has many relatively narrow streets lined with tall buildings. These“street canyons” hinder dispersion leading to high pollutant concentrations. Furthermore,the street canyons channel pollutants considerable distances along the street and fromstreet to street. For example, nitrogen dioxide concentrations in Cornmarket Street arecurrently in excess of the 40 µg m-3 objective despite there being no traffic in the street.

The situation is further complicated by the presence of bus stops in many of the streets.Buses often leave their engines running while stopped at the bus stops. Few data areavailable for estimating the rates of emission of pollutants from stationary buses withtheir engines running. Since the buses using the bus stops are the major source ofemission, there is considerable uncertainty in the estimates of the rates of emission. Thisuncertainty is increased where there is significant congestion because bus emissionfactors at low speeds are uncertain.

The ADMS Urban model is an up-to-date dispersion model and it is generally consideredto represent the state of the art. It contains a “street canyon” model to simulate thedispersion of pollutants in narrow streets. However, the model cannot take account of thechannelling of pollutants between street canyon sections or around junctions.Furthermore, it cannot fully take account of localised pollution sources within the streetcanyon such as bus stops.

Monitoring sites in Oxford city centre potentially affected by neighbouring street canyonsand by bus stops were identified. They were:

Park End StreetNew RoadWorcester StreetBeaumont StreetLongwall StreetHigh StreetTown HallCornmarket StreetGeorge StreetGeorge Street /Magdalen StreetHythe Bridge StreetBonn SquareHigh Street RPM

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The continuous monitoring site at the Town Hall is also potentially affected because it isclose to a number of bus stops and is near a crossroad junction between street canyons.

Fig.5.3 shows the modelled and measured nitrogen dioxide concentrations at diffusiontube sites, excluding the sites identified above. The diffusion tube measurements havebeen corrected on the basis of the collocated tubes at Town Hall. Also shown are linesrepresenting 1 to 1 equivalence between measured and modelled concentrations and thetrend line through the points. The model underestimates the concentration measured bydiffusion tube by typically 6 µg m-3.

Fig. 5.3: Comparison of measured and modelled nitrogen dioxide concentrations, 2002.City centre sites affected by bus stops and street canyons excluded (see text).Measurements based on diffusion tubes corrected according to bias determined at theTown Hall continuous site

Fig. 5.4 allows the same comparison between modelled concentrations and diffusion tubemeasurements corrected on the basis of collocated measurements at St Ebbes.

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40 45Modelled nitrogen dioxide concentration, ug/m3

Mea

sure

d ni

trog

en d

ioxi

de c

once

ntra

tion,

ug

/m3

20021 to 1Linear (2002)

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Fig. 5.4: Comparison of measured and modelled nitrogen dioxide concentrations, 2002.City centre sites affected by bus stops and street canyons excluded (see text).Measurements based on diffusion tubes corrected according to bias determined at the StEbbes continuous site

Fig. 5.5 shows the modelled and measured nitrogen dioxide concentrations at thediffusion tube sites listed above and excluded from Figs.5.3 and 5.4. No specialconsideration has been made to include the effects of bus stops in Fig. 5.5. The diffusiontube measurements have been corrected for measurement bias on the basis of thecollocated results at the Town Hall. Also shown are lines representing 1 to 1 equivalencebetween measured and modelled concentrations and the trend line through the points.The model underestimates the concentration measured by diffusion tube by typically 30µg m-3. This underestimation represents the contribution from buses at bus stops andfrom pollutants transferred from neighbouring street canyons.

0

5

10

15

20

25

30

35

40

45

0 5 10 15 20 25 30 35 40 45Modelled nitrogen dioxide concentration, ug/m3

Mea

sure

d ni

trog

en d

ioxi

de c

once

ntra

tion,

ug

/m3

20021 to 1Linear (2002)

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Fig. 5.5: Comparison of measured and modelled nitrogen dioxide concentrations, 2002.City centre sites affected by bus stops and street canyons only (see text). Measurementsbased on diffusion tubes corrected according to bias determined at the Town Hallcontinuous site

Further consideration was given to modelling the effects of bus stops in city centre streetcanyons. A survey was carried out to determine the times spent by buses with theirengines running at bus stops in the city centre. Rates of emission of oxides of nitrogenfrom the stationary buses were then estimated based on the emissions from the notionaldistance travelled by the buses at 5 kilometres per hour. These emissions were thenattributed to individual road sections within the ADMS Urban model and revisedpredictions made at the relevant diffusion tube sites. However, the revised predictionprovided no better agreement between modelled and measured concentrations than thatshown in Fig. 5.5.

5.5.3 Bias adjustment of the model

Bias adjustment is the process where the concentrations of the model are adjusted toagree with local air quality monitoring data. Clearly, the bias adjustment applied shouldcorrespond to the dispersion conditions in the area of model application. Bias adjustmenthas been done on the basis of Figs 5.3 and 5.4 for applications of the model that are notaffected by neighbouring street canyons or bus stops. Regression of the data providedthe following relationships (concentration units µg m-3):

1) Adjusted concentration =3.83+0.93 x Modelled concentration(based on diffusion tubes corrected on the basis of measurements at St Ebbes)

2) Adjusted concentration =4.48+1.08 x Modelled concentration(based on diffusion tubes corrected on the basis of measurements at Town Hall)

The standard deviations of the measured points about the regression line were 3.2 µg m-3

and 3.7 µg m-3 respectively. In practice, the corrected diffusion tube measurement lieswithin the range ± one standard deviation of the regression line at most sites and within

0

10

20

30

40

50

60

70

80

90

0 10 20 30 40 50 60Modelled nitrogen dioxide concentration, ug/m3

Mea

sure

d ni

trog

en d

ioxi

de c

once

ntra

tion,

ug/

m3

20021 to 1Linear (2002)

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± two standard deviations at nearly all sites. The standard deviation is similar to thatobtained for modelling studies elsewhere and represents an acceptable level ofuncertainty for the purposes of Review and Assessment.

For city centre applications potentially affected by neighbouring street canyons and busstops, regression analysis yielded the following relationship:

Adjusted concentration =30.5+0.86 x Modelled concentration(based on diffusion tubes corrected on the basis of measurements at Town Hall)

The standard deviation of the measured points about the regression line was 9.7 µg m-3.This value is relatively large and represents a substantial degree of uncertainty in themodel predictions. Consequently greatest emphasis has been placed in this Stage 4Review and Assessment on measured concentrations in the city centre area.

5.6 IMPROVEMENTS NEEDED IN AIR QUALITY

5.6.1 The improvement that is needed – general pointsA key step in the Stage 4 Review and Assessment process is to identify theimprovements needed in air quality, when there are exceedences of the UK air qualityobjectives.

An important point to note is that the Local Authority does not need to attempt toimprove air quality beyond the air quality objective that is being exceeded. This applieseven if that authority has taken a precautionary approach and deliberately set theboundary of their AQMA at, for example, the 36 µg/m3 contour rather than the 40 µg/m3

contour, in the case of the annual mean NO2 objective.

For example, an AQMA may have been declared for NO2, and for administrative reasons,the boundary of the AQMA may include houses where the concentrations of NO2 are notpredicted to exceed the annual mean objective of 40 µg/m3. Let us say the maximumexceedence of the annual mean NO2 objective at a relevant receptor in the AQMA was43 µg/m3. The maximum improvement that would be needed in this example AQMA willtherefore be 3 µg/m3. In this example, this will mean that some houses in the AQMA willexperience concentrations of NO2 possibly much lower than the annual mean objective.

5.6.2 Areas of predicted exceedence of the air quality objectives considered in this Stage 4 assessment

City Centre

Fig.5.6 shows the forecast concentrations for 2005 in the city centre area most affectedby bus stops in street canyons and the transfer of pollutants between street canyons.Fig.5.6 also shows the locations of the bus stops. The diffusion tube measurementsindicate that nitrogen dioxide concentrations in 2005 may reach 76 µg m-3 on the facadesof buildings in Queen Street, 73 µg m-3 in George Street and the High Street and 55 µgm-3 on St Aldates. Much of the building façade along these streets consists of shop frontsor offices: non-occupational exposure of members of the public will not occur at theselocations over the annual averaging time of the key objective for nitrogen dioxide.However, there is also residential occupancy of affected buildings, particularly associatedwith Oxford University colleges. For example, Balliol College is close to Magdalen Street,Pembroke College is close to St Aldates; University College, Queens College and LincolnCollege are close to the High Street.

The concentration of nitrogen dioxide would need to be reduced by 36 µg m-3 on QueenStreet, 33 µg m-3 on George Street and High Street and 15 µg m-3 on St Aldates. Takingaccount of background concentrations at St Ebbes of 23 µg m-3 and the non-linearity of

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the relationship between oxides of nitrogen concentrations and nitrogen dioxideconcentrations, it is expected that a reduction in local traffic emissions of at least 68% onQueen Street, 66% on George Street and High Street and 47% on St Aldates would berequired to meet the objective.

Fig. 5.6: Area of central Oxford with diffusion tube forecast concentrations for 2005 andbus stops

The Plain

The Plain and St Clements Street are at the eastern edge of the existing AQMA. The areaincludes significant areas of residential accommodation, including the Wainfleet Buildingclose to the Plain. Fig. 5.7 shows the modelled nitrogen dioxide concentration for 2005around the Plain with the model adjusted on the basis of collocated diffusion tubemeasurements at the Town Hall. Fig.5.7 also shows the locations of diffusion tubes atMagdalen Bridge, St Clements Street, York Place and Iffley Road. The forecast nitrogendioxide concentrations based on diffusion tube measurements similarly adjusted for biason the basis of measurements at Town Hall were 35 µg m-3 at Magdalen Bridge, 37 µg m-

3 at Iffley Road, 39 µg m-3 at York Place and 68 µg m-3 at St Clements Street. Themodelled predictions agree well with the diffusion tube forecasts, except at St ClementsStreet: however, the diffusion tube is sandwiched between two road signs and is unlikelyto provide a reliable measurement. The model results indicate that the objective of 40 µgm-3 may be exceeded at the facades of houses along St Clements Street as far as MorrellAvenue. The area of exceedence may also extend approximately 120 m along CowleyRoad from the Plain.

A similar model prediction may also be made using the model adjusted on the basis ofcollocated diffusion tube measurements at St Ebbes. Fig.5.8 shows the modelled nitrogendioxide concentration. The predicted area of exceedence of the 40 µgm-3 objective islimited to a small area of housing at the junction of St Clements Street and the Plain.

350 0 350 Meters

Map featuresHous ingKerbRoad centre

Diffusion tube forecasts, 2005, ug/m315 - 2930 - 3637 - 4041 - 5657 - 76

Busstops

N

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The existing AQMA extends approximately 100 m along St Clements Street from thePlain. Oxford City Council wish to adopt a conservative approach to the definition of theboundary of the AQMA. It is therefore recommended that the AQMA should be extendedalong St Clements Street as far as Morrell Avenue and approximately 120 m from thePlain along Cowley Road.

The predicted (Town Hall adjustment) nitrogen dioxide concentration at the façade ofhouses at the junction of St Clements Street and the Plain is 49 µg m-3. An improvementof 9 µg m-3 in nitrogen dioxide concentrations is required to meet the objective. Takingaccount of background concentrations at St Ebbes of 23 µg m-3 and the non-linearity ofthe relationship between oxides of nitrogen concentrations and nitrogen dioxideconcentrations, it is expected that a reduction in local traffic emissions of at least 35%would be required to meet the objective.

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Fig.5.7: Modelled nitrogen dioxide concentrations, 2005, near the Plain (model biasadjustment based on collocated diffusion tube at Town Hall)

350 0 350 Meters

Map featuresHousingKerbRoad centre

Merge1.shpBuildings

KerbRoad centre

Busstops

Theplain2.dxf40 ug/m 334 ug/m 328 ug/m 3

Fig.5.8: Modelled nitrogen dioxide concentrations, 2005, near the Plain (model biasadjustment based on collocated diffusion tube at St Ebbes)

350 0 350 Meters

Ma p fe atu resHo usingKerbRo ad centre

Me rge1 .shpBuild ings

KerbRo ad centre

Diffus io n tub e fo recasts, 2005 , ug /m315 - 2930 - 3637 - 4041 - 5657 - 76

Bussto ps

Th eplai n.d xf46 ug/m340 ug/m328 ug/m334 ug/m3

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St Giles and the University Science Area

The northern boundary of the existing AQMA lies across St Giles, extending southwardsfrom the junction of Pusey Street and St Giles. The University Science Area, includingParks Road, South Parks Road and St Cross Road lies to the east of St Giles and iscurrently outside the AQMA.

Fig.5.9 shows the modelled nitrogen dioxide concentration for 2005 around the north ofthe AQMA with the model adjusted on the basis of collocated diffusion tubemeasurements at the Town Hall. Fig.5.9 also shows the locations of diffusion tubes atPusey Street, Keble Road, Science Library, Parks Road, Mansfield Road, South ParksRoad, St Cross and Beaumont Street. The forecast nitrogen dioxide concentrations basedon diffusion tube measurements similarly adjusted for bias on the basis of measurementsat Town Hall were 37 µg m-3 at Pusey Street, 40 µg m-3 at Keble Road, 39 µg m-3 atScience Library and 34 µg m-3 at Parks Road, 29 µg m-3 at Mansfield Road, 36 µg m-3 atSouth Parks Road, 29 µg m-3 at St Cross Road and 50 µg m-3 at Beaumont Street. Themodelled predictions agree well with the diffusion tube forecasts, except at BeaumontStreet: however, Beaumont Street forms part of the city centre street canyon area andthe measurement is likely to be affected by bus stops on Magdalen Street and coachesoutside the Ashmolean Museum. The model results indicate that the objective of 40 µgm-3 may be exceeded at the facades of houses along the east side of St Giles as far northas the Woodstock Road. The model also predicts that the objective will be exceeded onthe east side of Parks Road north of South Parks Road.

A similar model prediction may also be made using the model adjusted on the basis ofcollocated diffusion tube measurements at St Ebbes. Fig.5.10 shows the modellednitrogen dioxide concentration. The predicted area of exceedence of the 40 µg m-3 islimited to a small area at the south end of St Giles.

The existing AQMA extends up St Giles approximately as far north as Pusey Street.Oxford City Council wish to adopt a conservative approach to the definition of theboundary of the AQMA. It is therefore recommended that the AQMA should be extendedalong the east side of St Giles as far as the Woodstock Road junction. Oxford City Councilmay also wish to consider including the east side of Parks Road in a separate new AQMA.Note that the Keble Road diffusion tube site is nearer to the road than residentialproperties in the area and so it is not representative of public exposure over the annualaveraging period of the objective.

The broad avenue of St Giles narrows at its southern end to join the more confinedstreets of Magdalen Street and Beaumont Street. The emissions from bus stops inMagdalen Street and from coaches outside the Ashmolean Museum increase theconcentrations markedly and the area is like the city centre area considered above:similar reductions in oxides of nitrogen emissions will be required to meet the air qualityobjective for nitrogen dioxide.

Further north, there is only a marginal risk of exceedence of the objective with predictedconcentrations at the building facades of 40 µg m-3. It follows that only marginalreductions in oxides of nitrogen emissions will be required to meet the objective. Thesituation is similar along Parks Road: only marginal reductions in emissions will berequired, if any.

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360 0 360 Meters

Map fea tu resHous i ngKerbRoad c en tre

Mer ge1 .s hpBu i ld ings

KerbRoad c en tre

D iffus ion tube fo rec as ts , 2005 , ug /m 315 - 2930 - 36

37 - 40

41 - 5657 - 76

Thepl a in.dx f46 ug /m 340 ug /m 328 ug /m 334 ug /m 3

Thepl a in2 .dx f40 ug /m 334 ug /m 328 ug /m 3

Sc ienc e .dx f46 ug /m 340 ug /m 334 ug /m 326 ug /m 3

Fig.5.9: Modelled nitrogen dioxide concentrations, 2005, near St Giles and the UniversityScience Area (model bias adjustment based on collocated diffusion tube at Town Hall)

360 0 360 Meters

Map featuresHousingKerbRoad centre

Merge1.shpBuildings

KerbRoad centre

Sc ience2.dxf40 ug/m334 ug/m326 ug/m3

Fig.5.10: Modelled nitrogen dioxide concentrations, 2005, near St Giles and theUniversity Science Area (model bias adjustment based on collocated diffusion tube at StEbbes)

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Banbury Road/Parks Road junction

The area included within the dispersion model extended some distance beyond theexisting AQMA. One of the areas outside the AQMA considered was the junction betweenBanbury Road and Parks Road.

Fig. 5.11 shows the modelled nitrogen dioxide concentration for 2005 around the junctionwith the model adjusted on the basis of collocated diffusion tube measurements at theTown Hall. It shows that the objective of 40 µg m-3 as an annual mean for nitrogendioxide may be exceeded at the end of one building close to the junction. Considerationshould be given to the potential for exposure of members of the public over the annualaveraging time of the objective. Oxford City Council may wish to investigate localconcentrations further by means of additional diffusion tube measurements inpreparation for the next round of review and assessment if there is significant publicexposure.

200 0 200 Meters

Map featuresHousingKerbRoad centre

Merge1.shpBuildings

KerbRoad centre

Diffusion tube forecasts, 2005, ug/m315 - 2930 - 3637 - 4041 - 5657 - 76

Banroad.dxf46 ug/m340 ug/m334 ug/m328 ug/m3

Fig. 5.11: Modelled nitrogen dioxide concentrations, 2005, near the Banbury Road/ParksRoad junction (model bias adjustment based on collocated diffusion tube at Town Hall)

Botley Road

The AQMA extends westwards from the city centre along the Botley Road as far as thestation railway bridge. It also extends along Oxpens Road from the Park End /RewleyRoad junction as far as Osney Lane.

Fig.5.12 shows the modelled nitrogen dioxide concentration for 2005 around the westend of the AQMA with the model adjusted on the basis of collocated diffusion tubemeasurements at the Town Hall. Fig.5.12 also shows the locations of diffusion tubes atBeckett Street, Osney Lane, the Station shops and Park End/Rewley Road. The forecastnitrogen dioxide concentrations based on diffusion tube measurements similarly adjustedfor bias on the basis of measurements at Town Hall were 35 µg m-3 at Beckett Street, 36

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µg m-3 at Osney Lane, 67 µg m-3 at Station Shops and 50 µg m-3 at Park End/RewleyRoad. The modelled predictions agree reasonably well with the diffusion tube forecastsat Beckett Street and Osney Lane. The model underestimates the diffusion tubeconcentrations at the Station Shops and Park End/Rewley Road: however, these two sitesare immediately adjacent to a group of bus stops. The model results indicate that thenitrogen dioxide concentrations may approach the objective of 40 µg m-3 at the facadesof shops and other buildings on the south side of the junction. The predicted area ofexceedence does not extend along the Botley Road beyond the railway bridge. Thepredicted area of exceedence does not extend significantly along Oxpens Road.

A similar model prediction may also be made using the model adjusted on the basis ofcollocated diffusion tube measurements at St Ebbes. The predicted concentrations areless than those predicted using model results adjusted on the basis of the Town Halldiffusion tube site.

On balance, the diffusion tube measurements and model predictions support the case formaintaining the existing boundary of the AQMA. Concentrations are high in theimmediate vicinity of the bus stop area and so the area close to the bus stops shouldremain in the AQMA. The model slightly underestimates the concentration at the OsneyLane diffusion tube site suggesting that the section of Oxpens Road between the ParkEnd/Rewley Road junction should remain in the AQMA on a precautionary basis.

The predicted (Town Hall adjustment) nitrogen dioxide concentration in the immediatevicinity of the bus stops at the Station Shops is 67 µg m-3. An improvement of 27 µg m-3

in nitrogen dioxide concentrations is required to meet the objective. Taking account ofbackground concentrations at St Ebbes of 23 µg m-3 and the non-linearity of therelationship between oxides of nitrogen concentrations and nitrogen dioxideconcentrations, it is expected that a reduction in local traffic emissions of at least 60%would be required to meet the objective.

Further from the bus stops only marginal exceedence of the objective of the 40 µg m-3

objective is predicted. It follows that only marginal reductions in oxides of nitrogenemissions will be required to meet the objective.

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290 0 290 Meters

Ma p fe atu resHo us ingKerbRo ad centre

Me rge1 .shpBuild ings

KerbRo ad centre

Diffusio n tub e fo recasts, 2005 , ug /m 315 - 2930 - 3637 - 4041 - 5657 - 76

Buss to ps

Bot ley .d xf46 ug/m340 ug/m334 ug/m328 ug/m3

Fig. 5.12: Modelled nitrogen dioxide concentrations, 2005, near Botley Road (model biasadjustment based on collocated diffusion tube at Town Hall)

Speedwell/Littlegate

The southern part of the existing AQMA includes St Aldates Road as far south as ThamesStreet, Speedwell Street and Littlegate and Old Greyfriars Street. The area includessignificant areas of residential accommodation.

Fig. 5.13 shows the modelled nitrogen dioxide concentration for 2005 around the southof the AQMA with the model adjusted on the basis of collocated diffusion tubemeasurements at the Town Hall. Fig.5.13 also shows the locations of diffusion tubes inthe area. The forecast nitrogen dioxide concentrations based on diffusion tubemeasurements similarly adjusted for bias on the basis of measurements at Town Hallwere:

39 µg m-3 at Folly Bridge23 µg m-3 at St Ebbes,28 µg m-3 at Shirelake37 µg m-3 at Thames Street36 µg m-3 at Butterwyke24 µg m-3 at Sadlers Walk27 µg m-3 at Thames /Oxpen34 µg m-3 at Oxpens Road44 µg m-3 at Speedwell Street/ Littlegate44 µg m-3 at Floyds Row40 µg m-3 at Faulkner Street30 µg m-3 at Norfolk Street23 µg m-3 at Paradise Square

The modelled predictions agree well with the diffusion tube forecasts. The model resultsindicate that the objective of 40 µg m-3 may be exceeded at the facades of residentialareas along St Aldates north of Thames Street, Speedwell Street and Littlegate and athouses backing on to Old Greyfriars Street. The predicted area of exceedence extendsslightly further south than the existing AQMA to include properties up to 30 m south ofthe junction between St Aldates Road and Thames Street.

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A similar model prediction may also be made using the model adjusted on the basis ofcollocated diffusion tube measurements at St Ebbes. Fig.5.14 shows the modellednitrogen dioxide concentration. The predicted area of exceedence of the 40 µg m-3 islimited to St Aldates Road including the junction with Speedwell Street and a small areaat the Littlegate end of Speedwell Street.

Oxford City Council wish to adopt a conservative approach to the definition of theboundary of the AQMA. It is therefore recommended that the AQMA should be extendedapproximately 30 m south of the junction between St Aldates Road and Thames Street.

St Aldates Road extends northwards into the heart of the city centre at Carfax. Thenorthern part of St Aldates Road is lined on both sides with bus stops and tall buildings.The improvement required in this city centre street canyon area has been consideredabove.

Concentrations along Speedwell Street are predicted to be approximately 44 µg m-3 in2005. An improvement of 4 µg m-3 in nitrogen dioxide concentrations is required to meetthe objective. Taking account of background concentrations at St Ebbes of 23 µg m-3 andthe non-linearity of the relationship between oxides of nitrogen concentrations andnitrogen dioxide concentrations, it is expected that a reduction in local traffic emissionsof approximately 20% would be required to meet the objective.

310 0 310 Meters

Ma p fe a tu resHo us ingKerbRo ad c ent re

Me rge1 .s hpBuild ings

KerbRo ad c ent re

Diffus io n tub e fo rec as ts, 2005 , ug /m 315 - 2930 - 3637 - 4041 - 5657 - 76

Bus s to ps

Spee dw ell.dx f46 ug/m 340 ug/m 334 ug/m 328 ug/m 3

Fig. 5.13: Modelled nitrogen dioxide concentrations, 2005, near SpeedwellStreet/Littlegate (model bias adjustment based on collocated diffusion tube at Town Hall)

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310 0 310 Meters

Map featuresHousingKerbRoad centre

Merge1.shpBuildings

KerbRoad centre

Busstops

Speedwell2.dxf40 ug/m 334 ug/m 328 ug/m 3

Fig. 5.14: Modelled nitrogen dioxide concentrations, 2005, near SpeedwellStreet/Littlegate (model bias adjustment based on collocated diffusion tube at St Ebbes)

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5.7 SOURCE APPORTIONMENT OF ‘BASE CASE’ PREDICTIONS

Source apportionment is the process whereby the contributions from the sources of apollutant are determined. In local air quality, the relevant sources could include: traffic;local background; industrial and domestic. Contributions from the different types ofvehicles (for example, cars, lorries and buses) can also be considered to highlight whichclass of vehicle is contributing most to the emissions from traffic. Source apportionmentallows the most important source or sources to be identified and options to reduceambient concentrations of pollutants can then be considered and assessed.

The source apportionment should:

• Confirm whether exceedences of NO2 are due to road traffic

• Determine the extent to which different vehicle types are responsible for the emissioncontributions to NO2 within Oxford’s AQMA. This will allow traffic managementscenarios to be modelled/tested to reduce the exceedences

• Quantify what proportion of the exceedences of NO2 are due to background emissionsor local emissions from busy roads in the local area. This will help determine whetherlocal traffic management measures could have a significant impact on reducingemissions in the area of exceedence, or, whether national measures would be asuitable approach to achieving the air quality objectives

5.7.1 What is the ‘base case’?The base case in this assessment is defined as the annual mean concentrations of NO2

that are predicted in the absence of any measures to improve air quality in Oxford.

5.7.2 Receptors considered

The following key receptors have been considered representative of areas in Oxfordwhere significant improvement in nitrogen dioxide concentrations may be required.

St Aldates Town Hall continuous monitoring site- typical of a receptor affected bybus stops near the junction between street canyonsJunction of St Clements and the Plain- typical of a busy road junction withoutbus stops.

5.7.3 Sources of pollution considered

We have considered the effect of the following sources in this Stage 4 assessment at thereceptors considered:

Background from sources outside the city centreTraffic-Light Duty Vehicles in the city centreTraffic-Heavy duty vehicles (including buses stopped at bus stops) in the citycentre

There is a complex relationship between oxides of nitrogen and nitrogen dioxideconcentrations: the relationship between the rates of emission of oxides of nitrogen andoxides of nitrogen concentrations is more direct. Source apportionment for the Town Hallhas therefore been carried out on the basis of measured oxides of nitrogenconcentrations at the Town Hall monitoring site. However, diffusion tubes measurenitrogen dioxide concentrations and do not measure oxides of nitrogen concentrationsand so the source apportionment at St Clements has been carried out on the basis ofnitrogen dioxide concentrations. The apportionment has been carried out on the basis of

netcen 48

estimated emissions on the local roads using emission factors for oxides of nitrogenprovided by DEFRA for Review and Assessment. Vehicle speeds were derived from theCounty Council’s Saturn traffic modelling. Sensitivity studies were carried out to assessthe influence of assumed traffic speeds.

A survey of bus waiting times at bus stops was carried out to determine average waitingtimes. Bus emissions from waiting buses were then estimated from the waiting time andthe emission factors for buses travelling at 5 kph. Emissions (including those fromwaiting buses) from High Street between Carfax and Turl Street, Queen Street betweenCastle Street and Carfax and from St Aldates between Pembroke Street and Carfax wereconsidered relevant to the source apportionment calculation for the Town Hall. Theaverage local contributions to emissions of oxides of nitrogen were as shown in Table 5.6for a range of assumed vehicle speeds.

Table 5.6: Local contributions to oxides of nitrogen emissions near the Town Hall

Scenario Vehicle emissions, g/sLight duty vehicles Heavy duty vehicles

in motionBuses at bus stops

Speeds from Saturnmodel

0.006 0.125 0.125

15 kph 0.006 0.143 0.1255 kph 0.007 0.252 0.125

Background sources were assumed to contribute 38.5 µg m-3 (from monitoring at StEbbes) to the measured concentration of oxides of nitrogen at the Town Hall of 185 µg m-

3. The identified sources thus contribute to the concentration of oxides of nitrogen at theTown Hall in the proportions shown in Table 5.7 for a range of assumed vehicle speeds.

Table 5.7: Proportion of oxides of nitrogen concentrations allocated to source categories

Scenario Percentage contribution to oxides of nitrogen concentrationsBackground Light duty

vehiclesHeavy dutyvehicles inmotion

Buses at busstops

Speeds fromSaturn model

20 2 39 39

15 kph 20 2 41 365 kph 20 2 52 26

It may be concluded that heavy duty vehicles, in particular buses, contribute the majorpart of the oxides of nitrogen emissions affecting the concentration at the Town Hall. Thevehicle speeds used in the source apportionment derived from the Saturn traffic modelassume that the traffic moves relatively freely. However, at peak times the roads nearthe Town Hall may become very congested, particularly when they are partially blockedby delivery vehicles servicing the shops. The emissions from slowly moving heavy dutyvehicles and buses increase markedly at slow speeds: it follows that heavy duty vehiclesin motion contribute a larger proportion as speeds fall as the result of congestion andbuses stopped at bus stops correspondingly less.

The modelled nitrogen dioxide concentration at the junction of St Clements with the Plainfor 2005 was 49 µg m-3. The background concentration based on measurements at StEbbes is forecast to be 23 µg m-3. The remaining 26 µg m-3 was allocated to heavy andlight duty vehicles in proportion to their calculated emissions on St Clements Street. The

netcen 49

identified sources contribute to the concentration of nitrogen dioxide in the followingproportions:

Background 47%Light duty vehicles 16%Heavy duty vehicles 38%

5.8 OPTIONS CONSIDERED TO IMPROVE AIR QUALITY AND THE EFFECTS OF THOSEOPTIONS

5.8.1 The options (Action Plan scenarios) considered

Oxfordshire County Council has considered a range of feasible options to improve the airquality in the city centre. These options will be included in the next review of the LocalTransport Plan, due in 2005.

In the context of the Oxford Transport Strategy policy it is not practical or realistic toreduce the number of buses and still meet the travel demands of the residential andworking population of Oxford. Over 40% of people travelling into central Oxford do so bybus. Therefore the key is to reduce the impact of buses rather than the total number.

The scenarios and measures put forward here (and within the Action Plan) need to bedeveloped and tested for effectiveness to assess the likely contribution to air qualityimprovements. Some of the measures are already in progress. Further measures can bedeveloped in the short/medium term. The longer term and larger scale measures wouldneed to go forward in to the next Local Transport Plan, due for submission in July 2005,to cover the period 2006 - 2010.

Table 5.8 summarises the proposed options and the obstacles to be overcome to allowthem to be implemented. The air quality impact of each option is discussed in turn below.

Table 5.8: Options to improve air quality

Measure Roadseffected

Current status Timescale Trafficimpact

bus gateenforcement

High StMagdalen StGeorge StCastle StNew Road

implementation2003/4; Execapproved; pendingstatutory powers (inprogramme)

short term medium

engine switch offwhile stationary(buses)

St AldatesHigh StCastle StMagdalen StButterwyke PlSpeedwell StNew Rd

powers available;Exec approvalrequired; aim forimplementation2003/4;enforcementprocedure to clarify

short term low/medium

higher emissionstandards - LEZ

all streets onbus priorityroute

legislation andenforcementprocess not clear –further funding andapprovals req’d

long term high

bus qualitypartnership

all streets onbus priorityroute

further devt andagreement with busoperators needed(in programme)

medium term medium

netcen 50

taxi qualitypartnership

all centralarea streets

Exec approved;further devt andagreement with taxicompanies needed– implementation2003/4 (in currentprogramme)

medium term low

bus boarding timeimprovements –Smart cardticketing

all centralarea streets;particularlywhere largenumber ofstops

in development bybus operators (?2003/4implementation) (incurrent programme)

short term –dependant onoperators

low

RoadreconfigurationWestgateredevelopment

2005/6 ? long term high

Station relocation 2006 + ? long term highGloucester Green– removal ofservices from GG

linked withWestgate redevtand Stationrelocation

long term high

(in programme – indicates that there is a current commitment to carry out the necessarywork or investigation)

5.8.2 Bus gate enforcement

Traffic is limited to buses and taxis throughout much of the day in parts of the city centrearea including the Carfax ends of High Street, Queen Street and St Aldates. However,access is allowed at certain times for delivery vehicles servicing the shops and thecovered market. Vehicles arriving outside the permitted hours often create additionalcongestion and reduce vehicle speeds. Small numbers of private cars also ignore theaccess restrictions. Stricter enforcement of the bus gate restrictions is expected toreduce the congestion. The effect of assumed vehicle speed on oxides of nitrogenemissions was shown in Table 5.6. If the average vehicle speeds were raised from 5 kphto the speeds predicted by the Saturn model (in the range 15-48 kph) it is estimated thatthe nitrogen dioxide concentration in 2005 would decrease from currently forecast valuesof 55 µg m-3 at the Town Hall to 44 µg m-3 (assuming a linear relationship betweenoxides of nitrogen emissions and nitrogen dioxide concentrations):

( ) 4423)125.0252.0007.0()125.0125.0006.0(.2355 =+

++++−

Thus reducing congestion in the city centre area has the potential to markedly reducenitrogen dioxide concentrations. However, reduction in congestion alone will not besufficient to meet the objective of 40 µg m-3 in 2005.

5.8.3 Switching off bus engines while stationary.

There is no central bus station in the city centre other than the coach station atGloucester Green. Buses wait at the central bus stops on St Aldates, Queen Street, HighStreet, Magdalen Street etc with their engines running often for several minutes. It ispredicted that eliminating the emissions from stationary buses would lead to a reductionin the currently forecast nitrogen dioxide concentration (calculated as above) at the Town

netcen 51

Hall of 55 µg m-3 to 39-45 µg m-3 depending on the assumed vehicle speeds. Thusswitching off buses while stationary in the city centre area has the potential to markedlyreduce nitrogen dioxide concentrations. However, this measure alone may not besufficient to meet the objective of 40 µg m-3 in 2005.

5.8.4 Higher emission standards

The Oxford Bus Company, upgraded its bus fleet so that 85% of it met the Euro IIstandard in 1999 as part of the bus quality partnership agreement between the City andCouncils and the bus operators. Other operators were not able to meet the targetalthough most of the buses meet the Euro I standard or better.

New buses currently meet the Euro III standard introduced in 2001. From 2005 onwardsnew buses will meet the Euro IV standard or better. The new standards provide forreduced emissions of oxides of nitrogen and other pollutants.

Table 5.9 shows emission factors for buses at 5 kph and at average urban speeds forrelevant emission standards. It also shows the percentage reduction in bus emissionsthat would result from conversion of all buses to Euro II, II and IV standards respectivelyfrom Euro II.

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Table 5.9: Emission factors for buses and potential reductions possible from upgradingfrom Euro II to Euro III standards

Emission factor, g/km % reduction from Euro II5 kph Average urban 5 kph Average urban

Euro I 20.76 10.77Euro II 17.72 9.66 0 0Euro III (2001) 12.229 6.67 31 31Euro IV (2005) 8.684 4.74 51 51

Conversion of all buses in Oxford city centre to Euro III standard is likely to lead to areduction in emissions of oxides of nitrogen of around 31% from current levels. Such areduction in emissions would lead to a reduction in the nitrogen dioxide concentrationfrom 59.5 µg m-3 in 2002 at the Town Hall to approximately 48 µg m-3 in 2005 comparedto the baseline forecast of 55 µg m-3. Thus further upgrading of the bus fleet buses in thecity centre area has the potential to markedly reduce nitrogen dioxide concentrations.However, this measure alone would not be sufficient to meet the objective of 40 µg m-3

in 2005.

5.8.5 Bus and taxi quality partnerships

A bus quality partnership agreement between the bus companies and the Councils wasset up prior to the implementation of the Oxford Transport Strategy. The County Councilhas proposed to develop this partnership further although details are not yet available.The council has also proposed a similar taxi quality partnership.

One of the key components of the existing bus quality partnership is the location of busstops. Bus stops are sited at locations convenient for public transport users as near aspossible to key commercial areas, including close to Carfax. Further consideration shouldbe given to relocation of bus stops where there is the potential for exposure of membersof the public over the relevant averaging time- a year. Relevant locations are listed inTable 2.4. Air quality impacts should not be given a high priority if there is little prospectof relevant public exposure.

5.8.6 Bus boarding time improvements

Various measures including Smart card ticketing have been suggested to improve busboarding times. Faster boarding might lead to some reductions in bus waiting times atbus stops and may ease congestion. These measures would contribute to potentialimprovement discussed above in 5.8.2 and 5.8.3.

5.8.7 Westgate development, road relocation, station relocation and Gloucester Green coach station relocation The redevelopment of the west end of the city would have a significant impact on airquality. However, these developments are not likely to take place before 2005.

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5.9 SIMPLE ASSESSMENT OF THE FEASIBILITIES OF THE OPTIONS CONSIDERED

This section of the report provides a simple assessment of the feasibility of the optionsconsidered to reduce or eliminate the chances of exceeding the air quality objectives forNO2 in Oxford. The data used has come from discussions between netcen and OxfordCity council. It is not intended as a full cost-benefit assessment; DEFRA do not requiresuch as analysis in a Stage 4 assessment.

If Oxford do go ahead and consider implementing one or more of the options, they willthen need to rigorously consider the costs and benefits of the options. Analytical toolsare available to do this, such as multi-criteria analysis. It is important that this step istaken because the decisions may be legally challenged and so need to be defensible.

The table below summarises the feasibilities and costs of the options in a simple way. Anoverall rank (1 being the ‘best’ option) is given. This is a purely subjective judgementand should not be used to base policy decisions upon. The best options is one that mightgive the greatest improvement in concentrations of annual mean NO2 for the lowest costand be possible to implement.

Table 5.10 Simple assessment of the feasibility of implementing the optionsconsidered to limit the concentrations of nitrogen dioxide in Oxford

Option(s)considered

Nitrogen dioxideconcentration, µµµµg m-3, 2005at Town Hall

Comments on feasibilityand cost

Rank

Baseline, plannedmeasures only

55

Bus gate enforcement 44 Costs associated withenforcement of existingpolicies- e.g. traffic wardens

1

Switching off busengines when stopped

39-45 depending onassumptions made

In principle appears feasiblebut unpopular with passengersand bus crews in winter.

3

Higher emissionstandards

48 May be expensive given OxfordBus Company’s previous outlayin upgrading to Euro II

4

Bus and taxi qualitypartnerships

Option not defined Review of bus stop locationswith respect to relevant publicexposure should be given highpriority

2

Bus boarding timeimprovements.

Option not defined Incremental improvementsseem likely as the result ofgeneral improvements inservice provision

Development of thewest end of the city

Option not defined Unlikely within timescale

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6 Implications of this Stage 4 air quality review and assessment forOxford

This section highlights the implications of this Stage 4 assessment for Oxford.

The section:

• explains any changes that may be needed to the current extent of the current AirQuality Management Area

• and comments on the effects that new national policy developments have had andmay have in the future on the predicted air quality in Oxford.

6.1 CHANGES TO THE AIR QUALITY MANAGEMENT AREA AS A RESULT OF THIS STAGE4 MODELLING

DEFRA have specified that the Stage 4 assessment must comment on any changes thatmight be necessary to extent of the AQMA as a result of the Stage 4 modelling.

The following table summarises any changes that might be needed.

Table 6.1 Summary of changes to the Air Quality Management Area in Oxford as aresult of this Stage 4 assessment

Name of area modelled Changes recommended to the existing AirQuality Management Area

City centre None. Consider public exposure over the annualaveraging time

St Clements and the Plain Extend the AQMA along St Clements Street asfar as Morrell Avenue and approximately 120 malong Cowley Road from the Plain

St Giles and theUniversity Science Area

Extend the AQMA along the east side of St Gilesas far as Woodstock Road

Junction of ParksRoad/Banbury Road.

None recommended, but consider potentialexposure of members of the public and reassessin the updating and screening assessment ifthere is significant exposure

Botley Road NoneSpeedwellStreet/Littlegate

Extend the AQMA approximately 30 m furthersouth along St Aldates

6.2 EFFECTS OF NEW NATIONAL POLICY DEVELOPMENTS

DEFRA have specified that the Stage 4 assessment must comment on any changes thatnew national policy developments may have had on the outcome of the air quality reviewand assessment process.

This Stage 4 has taken account of new Technical Guidance prepared by DEFRA Reviewand Assessment: Technical Guidance LAQM. TG(03). The Stage 4 has also taken accountof the most recent emissions factors published by the National Atmospheric Emissions

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Inventory on DEFRA’s behalf. These new developments have resulted in minor changes inthe recommended AQMA.

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7 The next steps for Oxford

7.1 OBTAINING DEFRA APPROVAL

DEFRA will need to approve this Stage 4 assessment. Oxford should now send a copy ofthe report to DEFRA. DEFRA’s assessors will provide a critique of the assessment,highlighting any matters that require further consideration. netcen would be pleased toassist Oxford City Council in addressing the matters arising.

7.2 LOCAL CONSULTATION ON THIS STAGE 4 ASSESSMENT

Oxford City Council can ask for feedback from stakeholders who may be interested in theoutcome of this Stage 4 air quality review and assessment. Important local stakeholdersmay include Oxfordshire County Council and adjoining local authorities (Vale of WhiteHorse, Cherwell, South Oxfordshire, West Oxfordshire), local residents in the AQMA, andthe planning and housing departments in Oxford City Council.

Efficient ways of disseminating the information include:

• placing the report on the local authority web site

• producing a small poster for display in the local authority offices

• producing a small poster for display in other public places (post offices, libraries etc.)

7.3 IMPLEMENTING THE OPTIONS IDENTIFIED TO IMPROVE AIR QUALITY

If Oxford wish to seriously consider implementing one or more of the options identified,they should now consider a more detailed cost benefit analysis. This could be completedas part of the Action Plan.

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8 References

C Buckingham, L Clewley, D Hutchinson, L Sadler and S Shah. London AtmosphericEmission Inventory. London Research Centre, 1997

CERC, 2000. ADMS-Urban. User Guide. Cambridge Environmental Research Consultants,2000.

DEFRA (2001) The air quality strategy for England, Scotland, Wales and NorthernIreland. A consultation document on proposals for air quality objectives for air qualityobjectives for particles, benzene, carbon monoxide and polycyclic hydrocarbons.Published by DEFRA in partnership with the Scottish Executive, The National Assembly forWales and the Department of the Environment for Northern Ireland.

DEFRA(2003). Review and Assessment: Technical Guidance. Part IV of the EnvironmentAct 1995. Local Air Quality Management. LAQM.TG(03).

DETR (2000) Concentrations of a range of air pollutants in the UK. Seehttp://www.aeat.co.uk/netcen/airqual/index.html

DETR (2000) Review and Assessment: Pollutant Specific Guidance. Part IV of theEnvironment Act 1995. Local Air Quality Management. LAQM.TG(00) May 2000.

DETR (2000) The Air Quality Strategy for England, Scotland, Wales and Northern Ireland.Department of the Environment, Transport and the Regions. Cm 4548, SE 2000/3, NIA 7.

DoE (1997) Department of the Environment. The United Kingdom National Air QualityStrategy. HMSO, March 1997. CM 3587.

AEA Technology (2000) Air Quality Review and Assessment - Stage 3 for Oxford CityCouncil. Report number AEAT/ENV/R/0434

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9 DEFRA compliance checklist

DEFRA Stage 4 requirements compliance checklistThis section has been introduced to indicate where the work expected by DEFRA in aStage 4 air quality review and assessment can be found in this document. Only nitrogendioxide is considered in this Stage 4.

Work area Included orconsidered?

Location within the report andcomments

Monitoring

• Has further monitoring been undertaken? yes 5.4

• Is the 'totality' of the monitoring effortsufficient?

• Has monitoring confirmed 2005 exceedances? yes 5.4.5

• Has sufficient detail of QA/QC procedures beenprovided?

yes Appendix 1

• Has monitoring amended the conclusions ofStage 3?

no 6.1

Modelling

• Has further modelling been undertaken? yes 5.6• Is the further modelling considered

appropriate?• Has the model been appropriately validated? yes 5.5.2, 5.5.3, Appendix 2• Has modelling confirmed 2005 exceedances? yes 5.6• Has modelling amended the conclusions of

Stage 3?no 6.1

General• Have both the magnitude and geographical

extent of any exceedences been furtherchanged?

no 6.1

• Has the decision to declare an AQMA beenreversed at Stage 4?

no 6.1

• Is this decision soundly based?• Has the authority taken account of the new

vehicle emission factorsyes 4.4

• Has the authority considered sourceapportionment?

yes 5.7

• Has the authority considered the costeffectiveness of different abatement options?

as far aspossible

5.9

• Has the authority considered feasibility andeffectiveness of different abatement options?

as far aspossible

5.8, 5.9

• Has the authority considered the extent towhich air quality improvement is required?

yes 5.6

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Work area Included orconsidered?

Location within the report andcomments

Monitoring & modelling work• Have monitoring uncertainties been addressed

fully?yes Appendix 1

• Does the additional monitoring assessmentappear sufficiently robust?

• Have modelling uncertainties been addressed? yes Appendix 2, 5.5.3• Has the model been carefully validated? yes Appendix 2• Does the overall modelling assessment appear

sufficiently robust?

AQO exceedances & AQMA declaration• Have areas of exceedence been further

defined?no 6.1

• Is the decision to amend or revoke theAQMA(s) at Stage 4, soundly based?

No decision taken yet to amend theAQMA

• Is the decision reached based principally onmonitoring?

• Is the decision reached based principally onmodelling?

General• Has the authority focused on areas already

identified as predicted to exceed objectives?yes 5.6

• Has consideration been given to the exposureof individuals in relevant locations?

yes

• Has the authority considered new nationalpolicy developments?

yes

• Has the authority considered new localdevelopments?

Noneidentified

• Does the report reach the expectedconclusions? (in part/full?)

• Has the authority undertaken further liaisonwith other agencies (in particular HA and EA?)

WithOxfordshire

CountyCouncil

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Appendices

CONTENTS

Appendix 1 Detailed monitoring data- St EbbesAppendix 2 Detailed traffic flow dataAppendix 3 Model validation - Nitrogen dioxide roadside concentrations

netcen

Appendix 1Detailed monitoring data-St Ebbes

CONTENTS

netcen

OXFORD ST EBBES January to December2000

These data have been fully ratified by netcen

POLLUTANT NOX NO2 NONumber Very High - 0 -Number High - 0 -Number Moderate - 0 -Number Low - 8008 -Maximum 15-minute mean 316 ppb 57 ppb 291 ppbMaximum hourly mean 296 ppb 51 ppb 271 ppbMaximum running 8-hour mean 201 ppb 41 ppb 181 ppbMaximum running 24-hour mean 129 ppb 32 ppb 109 ppbMaximum daily mean 112 ppb 27 ppb 92 ppbAverage of hourly means 19 ppb 10 ppb 9 ppbData capture of hourly means 91.2 % 91.2 % 91.3 %

Pollutant Air Quality Strategy Standard (Jan 2000) Exceedences DaysNitrogen Oxides (ppb) Annual mean > 16 ppb 1 -Nitrogen Dioxide Annual mean > 21 ppb 0 -Nitrogen Dioxide Hourly mean > 105 ppb 0 0

netcen

OXFORD ST EBBES January to December2001

These data have been fully ratified by netcen

POLLUTANT NOX NO2 NONumber Very High - 0 -Number High - 0 -Number Moderate - 0 -Number Low - 7528 -Maximum 15-minute mean 347 ppb 52 ppb 317 ppbMaximum hourly mean 312 ppb 49 ppb 286 ppbMaximum running 8-hour mean 205 ppb 37 ppb 184 ppbMaximum running 24-hour mean 180 ppb 33 ppb 159 ppbMaximum daily mean 161 ppb 32 ppb 140 ppbAverage of hourly means 23 ppb 12 ppb 11 ppbData capture of hourly means 85.9 % 85.9 % 86.1 %

Pollutant Air Quality Strategy Standard (Jan 2000) Exceedences DaysNitrogen Oxides (ppb) Annual mean > 16 ppb 1 -Nitrogen Dioxide Annual mean > 21 ppb 0 -Nitrogen Dioxide Hourly mean > 105 ppb 0 0

netcen

Oxford St Ebbes Air MonitoringHourly Mean Data for January to December 2001

Please contact for further information on air pollution in your area:Sean ChristiansenEnvironmental QualityAEA Technology plcCulhamAbingdonOxon OX14 3ED

Direct line01235 463521Direct facsimile01235 463011e-mail Sean.Christiansen@aeat.co.uk

NOX

400 ppb

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

NO

300 ppb

0

NO2

60 ppb

netcen

OXFORD ST EBBES January to December2002

These data have been fully ratified by netcen

POLLUTANT NOX NO2 NONumber Very High - 0 -Number High - 0 -Number Moderate - 0 -Number Low - 8224 -Maximum 15-minute mean 328 ppb 53 ppb 301 ppbMaximum hourly mean 296 ppb 52 ppb 271 ppbMaximum running 8-hour mean 220 ppb 42 ppb 195 ppbMaximum running 24-hour mean 138 ppb 31 ppb 117 ppbMaximum daily mean 138 ppb 31 ppb 117 ppbAverage of hourly means 20 ppb 11 ppb 9 ppbData capture of hourly means 93.9 % 93.9 % 94.8 %

Pollutant Air Quality Strategy Standard (Jan 2000) Exceedences DaysNitrogen Oxides (ppb) Annual mean > 16 ppb 1 -Nitrogen Dioxide Annual mean > 21 ppb 0 -Nitrogen Dioxide Hourly mean > 105 ppb 0 0

netcen

Oxford St Ebbes Air MonitoringHourly Mean Data for January to December 2002

Please contact for further information on air pollution in your area:Sean ChristiansenEnvironmental QualityAEA Technology plcCulhamAbingdonOxon OX14 3ED

Direct line01235 463521Direct facsimile01235 463011e-mail Sean.Christiansen@aeat.co.uk

NOX

300 ppb

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

NO

300 ppb

0

NO2

60 ppb

netcen

Oxford St Ebbes Air MonitoringHourly Mean Data for January to December 2000

Please contact for further information on air pollution in your area:Sean ChristiansenEnvironmental QualityAEA Technology plcCulhamAbingdonOxon OX14 3ED

Direct line01235 463521Direct facsimile01235 463011e-mail Sean.Christiansen@aeat.co.uk

NOX

300 ppb

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

NO

300 ppb

0

NO2

60 ppb

netcen

Appendix 2Detailed traffic flow data

netcen

Road Name 24-Hour Average % HGV includes buses andhgvs

Flow Speed %age HGVsN/E S/W N/E S/W N/E S/W

A34 986 1181 113 113 7.55 6.75A34 1187 1436 113 113 6.76 5.83A34 Average 1035 1224 113 113 6.69 7.06A34 North of slips 716 1225 113 113 10.27 5.93A34 North of slips 1456 1810 113 113 6.41 4.51A34 North of slips 868 1201 113 113 9.40 5.49A34 South of slips 1401 1916 113 113 6.18 4.55A34 South of slips 868 1201 113 113 9.40 5.49A34 South of slips 1339 1852 113 113 6.96 3.95A34 Southern Bypass 1287 1434 113 113 6.50 6.48A34 Southern Bypass 1287 1434 113 113 6.50 6.48A34 Southern Bypass 1287 1434 113 113 6.50 6.48A34 Southern Bypass 1287 1434 113 113 6.50 6.48A34 Southern Bypass 1287 1434 113 113 6.50 6.48A34 Southern Bypass 1287 1434 113 113 6.50 6.48A34 Southern Bypass 952 1098 113 113 7.32 7.14A34 Western bypass 1351 1539 113 113 5.81 6.31A34 Western bypass 1351 1539 113 113 5.81 6.31A34 Western bypass 1351 1539 113 113 5.81 6.31A34 Western bypass 1351 1539 113 113 5.81 6.31A34 Western bypass 1364 1539 113 113 5.81 6.31A34 Western bypass 1364 1539 113 113 5.81 6.31A34 Western bypass 924 1062 113 113 7.60 7.55A40 371 376 81 79 3.70 3.33A40 372 374 40 48 3.70 3.95A40 Elsfield Way 888 893 113 105 2.29 3.59A40 Elsfield Way 888 893 113 105 2.29 3.59A40 Elsfield Way 888 893 113 105 2.29 3.59A40 Elsfield Way 888 893 113 105 2.29 3.59A40 Elsfield Way 888 893 113 105 2.29 3.59A40 London Road 478 522 113 44 5.47 5.28A40 London Road 477 0 111 0 2.90 0.00A40 Northway 663 625 69 63 2.07 2.91A40 Northway 663 625 69 63 2.07 2.91A4142 North of Beaumont Rd 872 1069 113 98 2.49 2.66A4142 South of Beaumont Rd 864 1069 113 98 2.96 2.66A4144 Woodstock Road 347 484 32 48 5.90 3.99A4165 Banbury Road 440 453 33 46 5.50 7.78A4165 Banbury Road 387 349 48 48 6.87 7.99A4165 Banbury Road Average 392 389 42 47 6.26 7.87A420 461 561 98 113 2.38 3.30A423 292 451 90 113 3.73 2.00A423 292 451 90 113 3.73 2.00A423 292 451 90 113 3.73 2.00A423 Banbury Road Average 117 103 48 36 5.77 6.93A44 Woodstock Road 784 800 91 87 2.96 2.38Abingdon Rd North of link 515 550 29 22 3.97 3.76Abingdon Rd South of link 462 583 9 35 2.66 2.97Abingdon Road 377 350 22 48 9.00 9.00Abingdon Road 377 350 22 48 9.00 9.00Abingdon Road 458 439 48 27 7.00 6.00Abingdon Road 515 550 29 22 7.00 6.00Abingdon Road 480 571 20 29 3.35 3.36

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Road Name 24-Hour Average % HGV includes buses andhgvs

Flow Speed %age HGVsN/E S/W N/E S/W N/E S/W

Abingdon Road 462 583 9 35 2.66 2.97Banbury Nth of South Parade 363 360 48 48 6.48 7.81Banbury Nth of Squitchey Lane 369 381 33 46 5.50 7.78Banbury Nth of Thorncliffe Rd 418 414 48 37 5.83 7.55Banbury Rd Nth of BevingtonRd

306 371 48 46 7.46 6.04

Banbury Rd Nth of CanterburyRd

433 499 48 48 5.37 5.28

Banbury Rd Nth of Parks Rd 431 386 48 12 6.89 6.81Banbury Rd Sth of Parks Rd 309 275 18 48 7.63 7.85Banbury Road 432 427 21 47 5.34 5.54Banbury Road 447 447 48 48 5.37 5.37Banbury Road 447 447 48 48 5.37 5.37Banbury Road 447 470 48 48 5.37 5.54Banbury Road 306 258 48 48 7.61 8.88Banbury Road Average 354 295 48 29 6.06 7.88Banbury Road Average 355 376 42 38 6.72 6.31Banbury Road Nth of Five Mile Dr 47 48 1.00 1.70Banbury Road Sth of Five Mile Dr 292 231 48 31 5.45 6.96Banbury Sth of South Parade 387 349 48 48 6.87 7.99Banbury Sth of Thorncliffe Rd 326 243 48 13 6.58 8.60Barns Road/Blackbird Leys Road 32 43 44 22.92 22.92Barns Road/Blackbird Leys Road 32 43 44 22.92 22.92Barns Road/Blackbird Leys Road 32 43 44 22.92 22.92Bayswater Road 153 186 48 30 8.00 6.71Beauchamp Lane 123 72 40 42 3.17 2.17Beaumont Road 160 153 15 48 2.39 2.98Beaumont Street 245 273 48 22 4.00 4.00Beaumont Street 245 273 48 22 4.00 4.00Beaumont Street 245 273 25 48 4.00 4.00Becket Street 128 0 25 0 5.00 0.00Becket Street 0 0 0 0 0.00 0.00Between Towns Road 32 96 11 34 4.74 4.24Between Towns Road 14 4 48 33 10.14 4.56Between Towns Road 74 146 13 6 17.93 7.52Binsey Lane 47 58 48 23 2.30 1.77Blackbird Leys Road/Cuddesdon Way 210 41 48 22.92 22.92Blackbird Leys Road/Cuddesdon Way 210 34 48 22.92 22.92Blackbird Leys Road/Cuddesdon Way 210 41 48 22.92 22.92Blackbird Leys Road/Cuddesdon Way 210 41 48 22.92 22.92Blackbird Leys Road/Cuddesdon Way 210 34 48 22.92 22.92Botley East of Ferry HinkseyRd

308 300 27 25 5.64 6.39

Botley Road 450 517 22 13 3.96 3.62Botley Road 450 517 22 13 3.96 3.62Botley Road 373 371 48 40 5.97 5.53Botley Road 358 345 21 47 8.00 7.00Botley Road Average 315 259 24 38 5.80 6.01Botley West of Ferry HinkseyRd

358 345 21 47 5.97 5.56

Broad Street 18 30 20 48 2.79 5.67Broad St far west 0 69 0 12 0.00 43.00Butterwyke Place 30 0 20 0 60.00 0.00

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Road Name 24-Hour Average % HGV includes buses andhgvs

Flow Speed %age HGVsN/E S/W N/E S/W N/E S/W

Car park entrance 0 0 0 0 0.00 0.00Car park exit 0 107 0 7 0.00 1.00Cherwell Drive 151 245 48 34 1.64 1.67Cherwell Drive 151 245 48 34 1.64 1.67Church Cowley Road 270 279 48 20 7.00 6.00Church Cowley Road 340 320 47 48 7.00 6.00Copse Lane 264 129 47 34 0.10 0.84Copse Lane East of Eden Drive 240 143 48 48 0.26 1.00Copse Lane West of Eden Drive 310 103 46 15 -0.01 0.59Cornwallis East of Florence Pk Rd 35 41 1.00 0.32Cornwallis Road Average 72 34 41 34 1.69 2.06Cornwallis West of Florence Pk Rd 48 27 2.64 4.26Cowley Rd East of BullingdonRd

248 319 48 48 17.00 12.00

Cowley Rd East of James St 118 269 48 48 18.27 9.27Cowley Rd East of MagdalenRd

375 435 38 44 6.09 6.22

Cowley Rd East of StockmoreSt

144 278 45 46 16.30 8.94

Cowley Rd West of BullingdonRd

118 269 48 48 17.00 12.00

Cowley Rd West of James St 144 278 45 46 17.00 12.00Cowley Rd West of MagdalenRd

154 293 48 45 13.28 8.25

Cowley Rd West of StockmoreSt

145 238 48 37 17.00 12.00

Cowley Road 281 337 48 48 10.00 9.00Cowley Road (beyond Howard) 281 337 48 48 6.56 6.20Cowley Road (to Divinity) 248 319 48 48 8.95 7.28Cowley Road (to Howard) Average 385 41 45 8.17 7.03Cowley Road (to Marston) Average 271 47 42 16.30 9.56Cowley Road (to Union)Average

136 275 46 47 17.19 9.11

Cowley Road Average 189 296 48 48 11.96 8.19Crescent Road 78 50 44 41 1.53 1.99Crescent Road (Marsh Road) 78 50 44 41 1.53 1.99Cricket Road 58 166 48 44 1.44 3.40Cricket Road 58 166 48 44 1.44 3.40Crowell Road 1 5 17 48 4.00 5.00Davenant Road 31 22 45 45 0.00 0.00

0 0 0 0 0.00 0.00Divinity Rd North of Stone Street 130 69 32 32 0.79 -0.01Divinity Rd South of Stone Street 129 69 32 27 0.79 -0.01Divinity Road 312 270 15 32 0.679218274 0Divinity Road 129 69 32 29 0.79 -0.01Eastern Bypass 779 858 113 99 3.72 2.69Eastern Bypass 748 858 113 99 4.11 2.69Eastern Bypass 748 858 113 99 4.11 2.69Eastern Bypass 824 1122 85 113 2.84 2.99Eastern Bypass 824 1122 85 113 2.84 2.99Eastern Bypass 736 1005 30 113 2.83 2.64Eastern Bypass 868 936 113 87 2.63 1.66Eastern Bypass 868 936 113 87 2.63 1.66

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Road Name 24-Hour Average % HGV includes buses andhgvs

Flow Speed %age HGVsN/E S/W N/E S/W N/E S/W

Eastern Bypass 868 902 113 113 2.63 1.66Eastern Bypass 868 902 113 113 2.63 1.66Eastern Bypass 868 902 113 113 2.63 1.66Eastern Bypass 552 776 113 113 2.72 2.31Eastern Bypass (Oxford Rd) 367 366 35 15 3.05 2.09Five Mile Drive 17 146 42 35 4.01 1.70Five Mile Drive 17 146 42 35 4.01 1.70Ferry Hinksey Road 134 136 25 40 7.00 7.00

Garsington Road/Watlington Road 202 48 38 2.86 5.30George Street 67 78 27 27 50.00 48.00George Street 67 78 27 27 50.00 48.00George Street 24 21 27 27 89.57 31.35Godstow Road 61 44 21 48 2.97 2.51Godstow Road 1 0 48 0 4.00 0.00Godstow Road 61 44 21 48 2.97 2.51Gypsy Lane 147 120 21 26 1.57 1.57Headington Rd E of GypsyLane

237 320 15 28 11.06 7.97

Headington Rd W of GypsyLane

172 204 44 33 18.00 15.00

Headington Road 172 204 44 33 18.00 15.00Headington Road (London Rd) 348 331 47 18 8.00 7.97Headington Road Average 133 214 23 30 15.21 9.94Headley Way 735 664 15 17 1.47 1.00Headley Way 324 321 48 26 4.00 3.61Headley Way 324 321 48 26 4.00 3.61Headley Way Average 405 313 29 41 1.93 2.71Headley Way Nth of CopseLane

499 602 13 48 1.93 1.99

Headley Way Sth of CopseLane

396 292 48 48 1.86 3.24

Headley Way Sth of Eden Drive 404 333 46 18 2.30 2.96Headley Way Sth of Hospital 400 140 10 48 1.98 4.07Henley Avenue 313 227 48 41 3.99 4.91High Street 52 53 48 48 64.10 64.10High Street 56 55 23 48 64.10 64.10High Street 391 478 37 33 19.16 15.63High Street 391 478 37 33 19.16 15.63High Street East of Turl St 56 55 48 48 64.10 64.10High Street West of Turl St 47 50 35 27 64.10 64.10Hollow Way 357 178 44 29 3.42 3.46Hollow Way 357 178 44 29 3.42 3.46Hollow Way North of Crescent Rd 281 167 19 40 3.75 4.17Hollow Way South of Crescent Rd 48 20 3.90 5.85Hollow Way to Horspath Road Ave 136 31 33 3.84 4.78Hollow Way to Salegate Lane 197 95 48 20 3.90 5.85Hollybush Row (average) 240 301 9 23 0.99 1.80Hythe Bridge St (renamedcorrectly was Hollybush Row Nthof Park End St (outside RoyalOxford)

328 372 6 5 2.00 2.00

Hollybush Row Sth of Park End 229 292 14 44 0.99 2.12

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Road Name 24-Hour Average % HGV includes buses andhgvs

Flow Speed %age HGVsN/E S/W N/E S/W N/E S/W

StHolywell Street 3 3 48 20 0.00 0.00Horspath Driftway 596 348 48 43 1.96 1.18Horspath Road 83 148 48 20 2.43 1.98Horspath Road 83 148 48 20 2.43 1.98Horspath Road 341 323 48 48 2.89 2.66Howard Street 187 226 26 48 3.36 1.61Howard Street 0 139 0 34 0.00 0.76Howard Street 0 139 0 34 0.00 0.76Howard Street 0 139 0 34 0.00 0.76Hythe Bridge ????????? 0 0 0 0 0.00 0.00Hythe Bridge Street 363 341 25 21 0.99 1.08Iffley Road 259 197 46 48 4.56 5.85Iffley Road 343 197 45 38 3.99 5.85Iffley Road 383 381 48 6 5.00 5.00Iffley Road 409 305 15 48 4.00 5.00Iffley Road 360 360 15 48 3.53 4.05Iffley Road (to Bullingdon) Average 191 47 48 5.80 7.15Iffley Road (to Marston) Average 164 40 48 6.02 8.01Iffley Road North of James St 237 164 47 48 6.06 8.01Iffley Road North of StockmoreSt

226 164 33 48 7.00 8.01

Iffley Road South of James St 250 212 46 48 5.57 6.49Iffley Road South of StockmoreSt

237 164 47 48 6.06 8.01

Jack Straws Lane 36 29 42 41 0.99 0.61Jack Straws Lane 36 29 42 41 0.99 0.61Kingston Road Average 114 65 47 33 2.57 4.89Kingston Road Nth of LeckfordRoad

112 63 48 48 2.58 5.02

Kingston Road Sth of LeckfordRoad

125 73 46 20 2.52 4.74

Link 477 406 39 26 1.61 2.94Link 161 28 48 36 2.29 0.81Link 240 124 16 48 2.08 1.64Link 108 124 41 48 1.36 1.64Link 36 139 37 39 2.00 1.83Link 0 0 0 0 0.00 0.00Link 34 0 48 0 2.71 0.00Link ?????? 0 0 0 0 0.00 0.00Link ?????? 0 0 0 0 0.00 0.00Littlehay Road 108 84 36 39 1.20 1.72Littlehay Road 108 84 36 39 1.20 1.72Littlemore Road/Cowley Road 123 69 48 48 3.17 2.08London Place 437 363 34 33 7.98 8.56London Rd East of Gladstone Rd 410 459 34 48 7.45 6.33London Rd East of Wharton Road 385 236 48 48 7.48 10.70London Rd West of Barton Rd 385 236 48 48 7.48 10.70London Rd West of Gladstone Rd 396 406 44 17 8.47 7.64London Rd West of WhartonRoad

357 274 48 30 8.47 9.65

London Road 336 306 48 48 8.07 8.57London Road 326 258 24 45 8.48 10.70

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Road Name 24-Hour Average % HGV includes buses andhgvs

Flow Speed %age HGVsN/E S/W N/E S/W N/E S/W

London Road 404 403 42 37 7.79 7.76London Road 348 331 47 18 8.00 7.97London Road Average 368 259 48 38 7.95 10.13Longwall Street 311 237 48 26 5.00 4.49Magdalen Road 89 0 27 0 0.74 0.00Magdalen Road 89 0 27 0 0.74 0.00Magdalen Street East 0 69 0 12 0.00 43.00Magdalen Street West 71 0 12 0 44.00 0.00Margaret Rd East of Wharton Rd 48 85 38 45 6.47 0.70Margaret Rd West of Wharton Rd 48 48 6.47 0.70Margaret Road 43 85 48 41 6.85 0.70Margaret Road 43 85 48 41 6.85 0.70Margaret Road Average 48 85 43 46 6.47 0.70Marsh Lane 398 368 48 37 1.40 0.57Marston Ferry Rd 369 318 48 48 4.00 4.00Marston East 369 318 48 48 1.56 0.99Marston Ferry Road 369 318 48 29 4.00 4.00Marston Ferry Road - average 369 318 48 38 1.56 0.99Marston Ferry Road - average 369 318 48 48 1.56 0.99Marston Road 285 152 48 48 2.92 3.61Marston Road 346 186 48 36 2.98 3.00Marston Road 356 182 30 48 2.50 2.95Marston Road 346 186 48 36 2.98 3.00Marston Ferry Road 369 318 48 29 1.56 0.99Marston Ferry Road 369 318 48 48 1.56 0.99Moreton Road 94 22 17 30 1.52 -0.06Morrell Avenue 76 70 32 48 7.93 8.98Morrell Avenue 85 99 48 48 7.16 6.53Morrell Avenue 84 94 40 48 7.49 7.45Morrell Avenue East of Stone St 76 70 32 48 7.93 8.98Morrell Avenue West of Stone St 85 99 48 48 7.16 6.53New Road 102 72 48 21 46.00 61.00New Road 102 72 48 21 46.00 61.00Newman Road 121 74 33 33 5.57 1.46Castle Street 46 88 45 48 70.00 12.36Norfolk Street 76 0 17 0 1.22 0.00Norfolk Street 96 0 48 0 1.58 0.00Northway 664 611 102 113 2.95 4.16Northway 664 611 102 113 2.95 4.16Northway 664 611 102 113 2.95 4.16Northway 664 611 102 113 2.95 4.16Oakthorpe Road 1 0 36 0 10.00 0.00Old Greyfriars 101 71 48 17 69.00 19.00Old High Street 18 64 43 20 0.03 4.51Old Rd/Quarry Rd/Hollow/Beau. Rd 84 37 37 1.75 1.79Old Road 232 198 48 33 0.53 0.00Old Road Average 268 296 34 38 0.98 0.63Old Road East of Churchill Drive 307 410 25 48 1.82 1.42Old Road East of Lime Walk 298 295 31 28 0.52 0.00Old Road East of York Road 83 20 48 47 0.72 0.00Old Road West of Lime Walk 232 198 48 33 0.53 0.00Old Road West of York Road 83 103 48 10 0.72 0.51Osler North of Hospital Entrance 31 164 48 43 0.00 0.00

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Road Name 24-Hour Average % HGV includes buses andhgvs

Flow Speed %age HGVsN/E S/W N/E S/W N/E S/W

Osler Road 45 132 48 38 1.12 0.36Osler South of Hospital Entrance 61 99 48 28 1.73 0.98Osney Lane 31 37 28 48 1.00 4.42Oxford Rd (to Between TownsRd)

269 326 36 47 7.09 6.36

Oxford Rd East of Littlehay Rd 269 322 31 48 6.97 6.57Oxford Rd West of Littlehay Rd 269 346 40 45 6.99 6.15Oxford Road 269 346 40 45 6.99 6.15Oxford Road 248 374 19 21 6.29 4.55Oxford Road 180 339 39 38 6.22 4.31Oxford Road 1 29 19 37 1.66 3.52Oxford Road 180 339 39 38 6.22 4.31Oxford Road 180 339 39 38 6.22 4.31Oxford Road 1 29 19 37 1.66 3.52Oxford Road/Old Marston Road 84 48 43 39 0.65 0.97Oxpens Road 245 257 45 37 1.68 1.54Oxpens Road 245 257 45 37 1.68 1.54Oxpens Road 125 340 10 28 1.37 1.67Oxpens Road 198 315 24 18 1.30 1.69Thames St 265 292 12 40 0.99 1.70Park End Street 103 107 22 16 26.00 25.00Park End Street (Buses)Average

28 27 11 48 80.00 60.00

Park End Street (North laneSaid Business Sch)

338 272 8 8 2.00 4.00

Park End Street (W of BeckettSt)

308 243 27 25 5.64 6.39

Parks Rd Nth of South ParksRd

282 283 45 17 9.00 10.00

Parks Rd Sth of South ParksRd

36 55 21 31 9.00 10.00

Parks Road 295 283 19 48 9.00 10.00Parks Road 118 123 46 21 3.96 3.48Quarry Hollow 145 220 45 41 2.81 1.95Quarry Road 83 20 45 48 0.72 0.00Queen Street 32 0 43 0 100.00 0.00Rose Hill 206 174 40 48 5.02 5.64Rose Hill 335 290 48 48 1.50 1.63Rymers Lane 187 81 47 41 3.41 1.96Sandy Lane West 0 44 0 48 0.00 1.63Saxon Way/Dunstan Road 100 100 45 48 0.08 0.95Saxon Way/Dunstan Road 100 100 45 48 0.08 0.95South Parade 0 36 0 30 0.00 4.02South Parks Road 241 271 47 16 4.10 4.56South Parks Road 252 309 48 48 4.04 4.61Southern Bypass 1041 882 113 81 2.93 2.61Southern Bypass 909 882 65 81 2.94 2.61Southern Bypass 909 985 65 113 2.94 2.37Southern Bypass 960 908 79 45 2.90 1.97Southern Bypass 918 1005 93 113 2.66 1.66Southern Bypass 960 908 79 45 2.90 1.97Southern Bypass 918 1005 93 113 2.66 1.66Speedwell Street 157 135 10 48 22.00 51.00

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Road Name 24-Hour Average % HGV includes buses andhgvs

Flow Speed %age HGVsN/E S/W N/E S/W N/E S/W

St Aldates 135 238 48 15 33.00 53.00St Aldates 135 238 15 48 33.00 53.00St Aldates 81 133 11 23 20.29 19.97St Bernards Road 6 0 35 0 8.91 0.00St Clements E of Jeune Street 328 252 20 48 12.63 14.30St Clements Street Average 358 284 34 37 10.64 11.94St Clements W of Jeune Street 340 268 48 30 12.07 14.30St Cross Road 309 252 48 48 4.61 4.04St Cross Road 299 241 48 48 5.00 4.01St Giles 329 381 48 27 12.00 13.00Staverton Road 25 14 30 31 3.21 1.73The Slade 421 399 36 41 1.27 1.75The Slade 421 399 36 41 1.27 1.75The Slade 421 399 36 41 1.27 1.75Thorncliffe Road 0 74 0 31 0.00 4.89Walton Street 143 92 38 48 7.00 8.00Walton Street (average) 100 60 48 29 1.98 2.43Walton Street Nth of Lit.Clarendon

95 38 48 48 1.98 3.72

Walton Street Sth of Lit.Clarendon

103 120 48 20 4.00 3.00

Warneford Lane 312 281 34 37 1.99 2.54Weirs Lane/Donnington BridgeRoad

354 406 48 36 1.60 0.99

Weirs Lane/Donnington BridgeRoad

320 383 26 48 1.64 0.99

West Way 244 247 27 41 1.43 1.69Windmill Road 251 233 19 48 2.00 2.00Windmill Road 251 233 43 23 2.00 2.00Windmill Road (N of MargaretRd)

251 233 19 48 2.00 2.00

Woodstock Nth of BevingtonRd

182 269 48 48 10.92 7.32

Woodstock Nth of CanterburyRd

264 374 48 48 8.54 5.99

Woodstock Nth of Leckford Rd 235 353 48 46 9.42 5.99Woodstock Nth of SquitcheyLane

347 382 32 48 9.00 8.00

Woodstock Nth of ThorncliffeRd

318 411 48 48 7.43 5.60

Woodstock Road 347 382 32 48 5.90 3.99Woodstock Road 347 382 32 48 5.90 3.99Woodstock Road 255 341 48 48 7.94 4.98Woodstock Road 315 424 42 48 7.32 5.62Woodstock Road 362 464 48 47 7.40 5.64Woodstock Road 362 464 48 47 7.40 5.64Woodstock Road 82 196 48 48 20.86 8.99Woodstock Road 87 221 48 24 19.98 8.60Woodstock Road Average 301 392 39 48 5.64 3.99Woodstock Road Average 318 464 48 48 7.43 5.60Woodstock Road Average 228 330 48 47 9.52 6.35Woodstock Sth of SquitcheyLane

267 325 48 48 5.40 3.99

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Road Name 24-Hour Average % HGV includes buses andhgvs

Flow Speed %age HGVsN/E S/W N/E S/W N/E S/W

Woodstock Sth of ThorncliffeRd

318 485 48 48 7.43 5.60

Worcester Street (south) 73 112 48 13 48.00 33.00Worcester Street (north) 329 332 21 30 3.00 4.00Wytham Road 0 0 0 0 0.00 0.00Wytham Road 0 0 0 0 0.00 0.00Observatory Street 0 41 0 30 0.00 0.00Little Clarendon Street 0 64 0 30 0.00 0.00

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Appendix 3Model validationNitrogen dioxide roadside concentrations

CONTENTS

IntroductionModel application

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Appendix CModel validation-nitrogen dioxideroadside concentrations

CONTENTS

IntroductionLondon Study

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C1 INTRODUCTION

The dispersion model ADMS-Urban was used to predict nitrogen dioxideconcentrations at roadside locations in Oxford. ADMS-Urban is a PC-basedmodel that includes an up-to-date representation of the atmosphericprocesses that contribute to pollutant dispersion. It is described in some detailin a User Manual [CERC, 2000] The model was used to predict the localcontribution to nitrogen dioxide concentrations from roads.

The model has been used extensively for this purpose elsewhere and hasbeen verified by comparison with monitoring data obtained at a number ofroadside, kerbside or near-road monitoring sites in London [Carruthers et al,1999]. The comparison data are presented and discussed in C2.

C2 LONDON STUDY

C2.1 Model application

The London study carried out by Carruthers et al made use of an inventory ofemissions prepared by London Research Centre for Greater London [LondonResearch Centre, 1997]. The inventory included estimates of emissions of allsignificant identifiable sources within the M25 motorway, including those dueto utilities, industry, transport and domestic energy consumption. Emissionsdata were expressed for each individual source and also as total emissionsarising from 1 km x km Ordnance Survey national grid squares. The nominalbase year for the inventory was 1995 although road traffic emissions were fora 1996 base year. Emissions for other years after 1995/6 took account oftraffic growth predicted by the London traffic survey transport model andchanges in the emission performance of the vehicle fleet.

The model was used to predict concentrations for 1997 at monitoring stationsthroughout London. Meteorological data for 1997 from Heathrow Airport wasused to represent weather conditions. Background concentrations ofpollutants were provided by hourly data from a range of upwind rural sites.

The emission inventory provided estimates of oxides of nitrogen emissions.Nitric oxide is the main component of the oxides of nitrogen emitted fromcombustion sources. It reacts in the atmosphere, primarily with ozone, toform nitrogen dioxide. Nitric oxide is formed by the action of light on nitrogendioxide. The model included a generic reaction scheme to take account ofthese reactions.

C2.2 Comparison of predicted concentrations with measured values

Fig. C1 shows measured annual average nitrogen dioxide concentrationsplotted against the modelled values. A linear regression line is shown throughthe data points, with slope 1.01 and intercept -4.0 ppb. The standarddeviation of the difference between the measured value and thecorresponding point on the regression line was 3.15 ppb with 10 degrees offreedom.

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0

10

20

30

40

50

60

0 10 20 30 40 50 60

Modelled concentration, ppb

Mea

sure

d co

ncen

trat

ion,

ppb

Fig. C1: Comparison of modelled and measured concentrations of nitrogendioxide at London monitoring stations, 1997

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