Broxbourne Transport Strategy & Local Plan …...Broxbourne Transport Strategy & Local Plan Mitigation Assessment AECOM AECOM FINAL Broxbourne Transport Strategy 2017-08-10.docx 6/28

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Broxbourne Transport Strategy & Local Plan MitigationAssessment

Client nameBroxbourne Borough Council

DisciplineTransportation

Project nameCOMET Applications -Broxbourne TransportStrategy and Local PlanMitigation Assessment

Date10th August 2017

Project number60522529

Prepared byAY

Reviewed byJKF

Approved byCM

Revision History

Revision Revision date Details Authorised Name Position

1 04/07/2017 Draft

2 10/08/2017 Final withComments

AECOMAECOMFINAL Broxbourne Transport Strategy 2017-08-10.docx 2/28

Executive Summary

AECOM have tested a series of highway and sustainable transport interventions for Broxbourne BoroughCouncil (BBC) using Hertfordshire’s County Model of Transport (COMET), the results of which can be foundin more detail in this technical note. This is to examine the effects of revised planning data assumptions andthe application of a range of transport interventions, for comparison with work being undertaken by WYG onbehalf of BBC. This in turn will help to define transport mitigations to support planned local growth.

Two scenarios have been modelled using COMET for model year of 2031. A “Do Minimum” scenario; for thisscenario, the highway network is made up from the base year network, plus all committed schemes as definedby Hertfordshire County Council until 2031; and a “Do Something” scenario; the highway network for thisscenario takes the “Do Minimum” network, and adds in a series of highway and sustainable transportinterventions as defined by Broxbourne Borough Council. In both scenarios the demand assumptions usedare the same, based on revised planning data provided and therefore, differences between the two scenariosare as a result of the series of highway and sustainable transport interventions.

Results have been assessed using four key indicators:

· Flow differences:

─ This is the difference in vehicle flows between the two scenarios.

· Junction Delay:

─ Junction delay is defined by the average delay for all possible turns at the given model node,weighted by the vehicular flow making each turn. Note that the delay for a specific turn at a junctionmay therefore be significantly higher or lower than this value indicates, but the defined measuregives an overall impression of junction operation.

· Link Stress:

─ Link stress is calculated by SATURN as a ratio of volume over capacity (V/C) for a given link. Linksare generally considered to be approaching capacity at 80% V/C, beyond which there is a materialdeterioration in operation. Note that the length of the modelled queue on amber/red links is notrelated to the length of the link in the plot. The V/C value calculated by SATURN relates to the linkas a whole, however, the queue may not extend along the whole link (particularly if the link is long).The extent of the queueing should therefore also be interpreted using the junction delay circles.

· Modal Split Changes:

─ This is the percentage share of trips by either Car, Public Transport or Active Modes (i.e. Walkingand Cycling)

Analysis of the results has lead to the following key findings from the modelling:

· Junction delay reductions on the A10 as a result of the schemes introduced. Ban on right turnsat College Road and Church Lane improve the junction performance.

· Proposed interventions do not draw in demand to the A10 from the wider strategic roadnetwork.

· Some localised re-routeing in Broxbourne/Hoddesdon has a results of the 20mph scheme onthe A1170 (Old A10) with reduced flows along the A1170 itself.

· Sustainable Transport Interventions do not appear to have had a noticeable impact on themodal splits for journeys in Broxbourne.

COMET has been developed as a strategic countywide model and has not been developed specifically torepresent traffic conditions in urban areas. The model has not been validated inside urban areas. Therefore,this should be taken into account when interpreting the results within Broxbourne.

Testing the interventions in COMET allows the impacts of the interventions to be evaluated in respect to thewider strategic road network in Hertfordshire. The modelling shows these effects to be relatively localisedwithin the Borough of Broxbourne and does not draw in latent demand from the wider strategic road network,especially in respect to the interventions along the A10.

Broxbourne Transport Strategy & Local Plan Mitigation Assessment


1. Introduction

1.1 Background

1.1.1 Broxbourne Borough Council (BBC) is producing a Local Plan and as part of this a Transport Strategyis being developed. This will highlight the mitigation required to facilitate the planned growth andaccommodate the increase in travel demand which will arise as a result of planned new houses andjobs to be provided by 2031.

1.1.2 A number of highway mitigation options were tested through BBC’s highway-only SATURN model bytheir consultants, WYG. BBC have subsequently commissioned AECOM to utilise Hertfordshire’sCounty Model of Transport (COMET) to ascertain the implications for both the local transport networkand impacts further afield, of a preferred package of multi-modal measures drawn out within theTransport Strategy.

1.1.3 The aim of this modelling test is to demonstrate if the preferred proposed package of multi-modalmeasures effectively mitigates the impact of the growth envisaged within the Broxbourne Local Plan.The test also looks to determine whether these measures can provide the network capacity to caterfor an increase in travel demand, and provide realistic alternatives to reduce reliance on the car andencourage modal shift.

1.1.4 AECOM have therefore been commissioned by Broxbourne Borough Council to undertake runs ofCOMET and report on the effect that the mitigation measures have on flows, junction delays, linkstress and modal splits in Broxbourne.

1.2 Scope of Work

1.2.1 The scope of work AECOM have been commissioned to carry out was broken down into the followingkey stages:

· Initial Scheme and Planning Data Review;

· WYG Broxbourne SATURN Model Comparison;

· Produce a 2031 COMET Local Plan Do-Minimum Scenario and a 2031 COMET BroxbourneDo Something Scenario; and

· 2031 COMET Local Plan Do-Minimum and 2031 COMET Broxbourne Do Something ScenarioModel Comparison.

1.2.2 Prior to the commissioning of this work, advice was given to BBC about the ability of COMET tomodel certain schemes. Subsequently, a package of multi-modal schemes was provided to AECOMby WYG/BBC to code into the 2031 COMET Broxbourne Do Something scenario. This has beensummarised in a technical note “Broxbourne Transport Strategy Modelling Assumptions 2017-06-08_Final.pdf” provided to BBC.

1.2.3 AECOM were then provided with WYG’s highway only Broxbourne SATURN model. The purpose ofthis was to allow consistency in the coding of schemes between WYG’s Broxbourne SATURN modeland the 2031 COMET Broxbourne Do Something scenario.

1.2.4 Updated planning data assumptions were also provided to AECOM. As these assumptions weredifferent to those in the 2031 Do Minimum scenario, this needed to be updated and re-run. The sameplanning data assumptions were also applied to the Do Something, so that the only differences whencomparing the Do Minimum and Do Something relate to the schemes. The re-running of the DoMinimum and Do Something with revised planning data assumptions was undertaken to minimiseany differences between the COMET model and the WYG model.



1.2.5 This technical note reports on the results of the model comparison of the COMET Do Minimum andDo Something.

1.3 Caveats

1.3.1 COMET has been developed as a strategic countywide model and has not been developedspecifically to represent traffic conditions in urban areas. The model has not been validated insideurban areas. The model’s main purpose is to simulate inter-urban movements in Hertfordshire, andthe calibration/validation process has been conducted accordingly. This has an implication on thelevel of confidence that can be placed on results in the urban areas of the Broxbourne district.

1.3.2 The highway assignment component of the COMET model suite is in SATURN, which is a tool thatsuits the strategic geographical scale of COMET, however does not enable investigation of detailedsections of the highway network (e.g. detailed junction or corridor assessment).

1.3.3 Further evidence may be required to underpin and understand specific network issues as well asspecific developmental impacts as they come forward. At this stage, therefore, the results presentedhere should be interpreted as high level indications of likely traffic conditions.

1.3.4 It should be noted that there are differences in nature between the COMET model and WYG’shighway only model, and therefore it is possible that the outputs will reflect these.

1.4 Structure of this note

1.4.1 This note is presented in the following sections:

· Review of Base Year (2014) Model Performance;

· Review of Scheme Coding;

· Review of Planning Data;

· 2031 COMET Local Plan Do Minimum Scenario Traffic Conditions;

· Broxbourne 2031 COMET Do Something vs 2031 COMET Local Plan Do Minimum; and

· Summary.



2. Review of Base Year (2014) Model Performance

2.1.1 This section of the document summarises the performance of the COMET highway assignmentmodel in the Borough of Broxbourne according to Department for Transport (DfT) WebTAG(Transport Analysis Guidance) criteria. The performance indicators provided are those that weredefined during the model development process, and are categorised as follows:

· Journey time validation routes;

· Screenlines and cordons validation; and

· Link flow Validation.

2.1.2 It should be noted that the COMET model has been used as it currently stands, due to availabletimescales which did not allow for the revisiting of local validation.

2.2 Journey Time Validation

2.2.1 During the development of COMET, one journey time route passed through the Borough ofBroxbourne for the purpose of model validation, as shown in Figure 1. Journey times along theseroutes are compared between the model and observed (TrafficMaster 2014-15 journey time) data.

2.2.2 WebTAG recommends that modelled and observed journey times should be within 15% (or withinone minute, if higher than 15%)1. Figure 1 has been annotated according to whether the journeytime route meets this criterion. Full results for the journey time validation are provided in Table 1.

Table 1. COMET Journey Time Validation Results in Broxbourne. Route 13A: A10 (Rush Green – M25)

Direction Observed(seconds)

Modelled(seconds)

Difference(seconds)

% Difference WebTAGCompliant?

AM IP PM AM IP PM AM IP PM AM IP PM AM IP PMNorthbound 711 720 817 692 691 757 -19 -30 -60 -3% -4% -7% YES YES YESSouthbound 1,032 725 833 716 671 724 -317 -55 -108 -31% -8% -13% NO YES YES

1 Tag Unit M3.1 Highway Assignment Modelling. Table 3.



Figure 1. COMET Journey Time Validation Routes in Broxbourne

2.2.3 The route performs well in all directions and time periods with the exception of the morning peaksouthbound route where the delays are under estimated.

2.3 Flow Validation (screenlines and cordons)

2.3.1 Another measure of model performance is the extent to which it represents the volume of traffic intoand out of towns (cordons), and the volume of traffic across screenlines. WebTAG recommends thatthe difference between modelled and observed flow across screenlines and cordons should be lessthan 5%2.

2.3.2 Figure 2, Figure 3 and Figure 4 show the locations of the screenlines and cordons in theBroxbourne area. They also indicate through colour coding the difference between modelled andobserved flow.

2 TAG Unit M3.1 Highway Assignment Modelling. Table 1.



2.3.3 The Broxbourne cordon for the morning and evening peaks perform within WebTAG guidelines. Ingeneral there is a good level of validation on screenlines with flows within WebTAG guidelines, withthe exception of eastbound flows on the screenline to the east of Broxbourne and the screenline tothe north which generally underestimates demand in the morning and evening peak hours for thenorthbound flows.



Figure 2. Morning Peak Screenline and Cordon Validation Results



Figure 3. Inter-Peak Screenline and Cordon Validation Results



Figure 4. Evening Peak Screenline and Cordon Validation Results



3. Review of Scheme Coding

3.1 Introduction

3.1.1 AECOM have been provided with a list of highway infrastructure schemes by BBC and theirconsultants WYG. These cover 25 locations on the highway network, and the schemes also includepublic transport mitigations and active modes improvements, namely improvements to cycle ways.

3.1.2 This section provides an overview about these schemes, which have been coded in the Broxbourne2031 COMET Do Something scenario.

3.1.3 A technical note was previously issued to BBC containing all of the modelling assumptions ofschemes to be coded titled “Broxbourne Transport Strategy Modelling Assumptions 2017-06-08_Final.pdf” and contains more details on how the schemes have been coded and the assumptionsbehind them. This is included as an appendix to this technical note for completeness.

3.2 Highway Schemes

3.2.1 BBC’s consultants WYG have identified 25 highway scheme mitigations and modelled them usingtheir Broxbourne Highway SATURN model. The location of these schemes are in Figure 5 and moredetailed coding assumptions are provided in the Modelling Assumptions technical note which ispresented in Appendix E.

3.2.2 The highway mitigation measures contain a range of improvements. They contain schemes such asconverting small or mini roundabouts into signalised junctions to larger changes at key junctions. Forexample creating a hamburger roundabout at the Park Plaza North roundabout on the A10. A full listof the highway scheme improvements is presented in Appendix A.

3.2.3 The scope of work as agreed with BBC was to ensure the network coding was as consistent aspossible with WYG’s Broxbourne Highway SATURN model. As a result, signal timings have beenkept consistent with the WYG Broxbourne Highway SATURN model in order to determine the impactof these schemes and no signal optimisation was carried out.



Figure 5. Broxbourne Highway Schemes

3.3 Sustainable Transport Interventions

3.3.1 In addition to the Highway Schemes mentioned above, sustainable transport interventions have beenincorporated into the COMET model based on details provided by BBC and WYG. These combine arange of bus, rail and cycle improvements.

3.3.2 Four new bus services and a revised route have been added to cater for the new development sitesalongside infrastructure improvements across the borough. The assumed frequencies of the newbus services are documented in Appendix B. The delays in the Do Minimum model were used tocalculate the expected delay differences from the bus priority measures to apply the resultant journeytime improvements to the relevant routes.



3.3.3 For rail, two new stations have been included at Turnford and at Park Plaza. At Park Plaza, theexisting Overground service has been amended to call at this station, whilst at Turnford new Crossrail2 services have been modelled to call at this station. At the existing Waltham Cross, Cheshunt andBroxbourne stations, services and stopping patterns have been adjusted to match the assumptionsspecified and included in the modelling assumptions document “Broxbourne Transport StrategyModelling Assumptions 2017-06-08_Final.pdf” which is included in Appendix E.

3.3.4 Cycling interventions have also been included in the modelling. A network of new and improved cyclepaths has been modelled in the network. Depending on the nature of the cycle paths (i.e. off-roadsegregated, on-road segregated and on-road non-segregated), varying factors as specified by theDfT’s data book have been applied to the active mode link lengths to represent the attractiveness ofthe type of cycle lane.

3.3.5 The specification note defined the methodology applied. Cycling intervention expected changes werecalculated away from the COMET model and then applied to the active mode network. Spreadsheetcalculations were used to work out what adjustments needed to be applied based on the proportionof cyclists and suggested WebTAG values on the level of intervention. This provided an expectedchange. This was applied to the active mode link lengths in the model to represent the change.Appendix B to D contains the specific information about the bus, rail and cycle links coded into the2031 COMET Broxbourne Do Something scenario.



4. Review of Planning Data

4.1.1 Differences between the Do Minimum and Do Something model runs would have to be as a result ofthe mitigation measures specified in section 3. This means the underlying planning data needed tobe consistent between both models.

4.1.2 BBC supplied AECOM with planning data to use for the Do Minimum and Do Something scenario.The original scope of the work did not allow for an update in planning data, and it was originallyplanned to make use of the existing 2031 COMET Local Plan scenario completed by AECOM in2016. However, for consistency with the WYG planning assumptions it was agreed that the COMETDo Minimum and Do Something scenarios would be updated.

4.1.3 The sites with significant changes in developments included in the planning data are:

· Dwellings:

─ High Leigh Garden Village;

─ Brookfield Riverside/ Garden Village;

─ Cheshunt Lakeside; and

─ Rosedale Park

· Jobs:

─ Brookfield Riverside;

─ Cheshunt Lakeside Relocation

─ Park Plaza

4.1.4 The planning data used was agreed with BBC and summarised in the document “BroxbourneTransport Strategy Modelling Assumptions 2017-06-08_Final.pdf”. This document also shows theoriginal planning data used for the previous 2031 COMET Local Plan scenario for comparison of thechanges. This document has also been provided in Appendix E.



5. 2031 COMET Local Plan Do Minimum Scenario Traffic Conditions

5.1 Introduction

5.1.1 This section presents the results from the 2031 COMET Local Plan Do Minimum scenario. The 2031Local Plan Do Minimum scenario has been re-run with changes to the planning data, as explainedin section 4. This scenario has been previously defined by Hertfordshire County Council (HCC)containing only local plan growth and likely infrastructure schemes and therefore excludes themitigation proposed by BBC.

5.2 Traffic Conditions

5.2.1 Figure 6, Figure 7 and Figure 8 display junction delays in the three time periods alongside theVolume-over-Capacity (V/C) ratio on highway links.

5.2.2 The modelling shows traffic conditions in the 2031 COMET Local Plan Do Minimum Scenario arevery similar in nature throughout the three time periods. The modelling results indicate junction delaystend to be focused towards the Cheshunt area. The A10 corridor has delays up to 1.5 minutes acrossmultiple junctions, mainly in the Cheshunt area, while delays are also observed on junctions alongthe Old A10 by Hoddesdon.

5.2.3 Delays are identified at the following junctions along the A10:

· A10 / Park Plaza;

· A10 / Lieutenant Ellis Way;

· A10 / College Road; and

· A10 / Church Lane.

5.2.4 Another junction delay that consistently appears across all scenarios is the access to Tesco onHalfhide Lane (West of A10). Delays at Church Lane/High Street and College Road/Turners Hillroundabouts east of A10 appear in the inter-peak and evening peak due to the higher level of trafficusing east-west movements to access the Cheshunt urban area.

5.2.5 In Lower Nazeing, there is large delay identified at the Nazeing Road / St Leonards Road signalisedjunction as shown in Figure 6. This junction is operating with a V/C over 80% in the evening peakand over 90% in the morning peak in the Do minimum with a slight reduction in the Do somethingV/C ratio. Flow difference plots (Figures 9, 10 and 11) show only a slight reduction in flows comingfrom the east on this link.

5.2.6 Two further junctions with minor delays have also been identified in the modelling. In Broxbourne,the A1170/Station Road shows delays each time period. Towards Hoddesdon, the A1170/Cock Laneroundabout also experiences minor delays however only in the morning peak.



Figure 6. 2031 COMET Local Plan Do Minimum, V/C and JunctionDelays, Morning Peak

Figure 7. 2031 COMET Local Plan Do Minimum, V/C and JunctionDelays, Inter-Peak



Figure 8. 2031 COMET Local Plan Do Minimum, V/C and JunctionDelays, Evening Peak



6. Broxbourne 2031 COMET Do Something vs 2031 COMET Local Plan DoMinimum

6.1 Introduction

6.1.1 This section compares the Broxbourne 2031 COMET Do Something Scenario and the 2031 COMETLocal Plan Do Minimum Scenario. As mentioned previously, COMET is a strategic model and theresults presented in this section should be interpreted at a high level.

6.2 Modelled Flow Difference

6.2.1 The analysis of the flow differences between both scenarios are presented in Figure 9, Figure 10and Figure 11.

6.2.2 Due to the ban of right turns at the A10 junctions with College Road and Church Lane, the A10 is amore attractive option under the Do something Scenario as a result of the reduced delays at the twojunctions. There is some re-routeing as a result of some localised delay in the area as a result ofschemes either side of the A10 with Church Lane. Schemes 7 and 8, at the junctions of Church Lane/ High Street and Church Lane/Flamstead End Road, increase the delays and as a result vehiclesare re-routing further south and using College Road instead.

6.2.3 Overall the modelling is showing that the schemes along the A10 do not attract more trips to the areaand that the flow differences presented in Figures 9, 10 and 11 are a result of more localised re-routeing in response to the schemes.

6.2.4 A reduction in trips is observed along the Old A10 (A1170) between Hoddesdon and Cheshunt. Thisis likely to be due to a combination of the 20mph scheme along this route, together with changesmade on the parallel rail line proving to be an attractive option.

6.2.5 As a result of the 20mph scheme along the A1170, some localised re-routeing is observed inHoddesdon and Broxbourne. Re-routeing is observed for trips now using the parallel Baas Lane,Park Lane and Cock Lane to access the zones in this area. Previously vehicles would remain on theA1170 to the A1170 / Cock Lane Roundabout to access this area.

6.2.6 Trips travelling eastbound from Hoddesdon via Lower Nazeing are observed to re-route in themodelling via Essex Road, Dobbs Weir Road, Sedge Green and North Street, thereby increasingtraffic at these locations. These trips are avoiding the A1170 as a result of the 20mph scheme.

6.2.7 Away from Broxbourne Borough, in the morning peak there is a noticeable flow difference in Hertford.Minor re-routeing into Hertford Town Centre causes some additional delays at the Bluecoatsroundabout. The Bluecoats roundabout operates at capacity and as such the change in delays resultsin the localised re-routing as seen.

6.2.8 In examining M25 Junction 25, it is noted that capacity increases are included although thecomparison plots suggest a reduction.in demand which is the result of the addition of a new link toprovide a dedicated left turn lane, and which therefore cannot be directly compared to older coding.



Figure 9. 2031 Flow Differences, Broxbourne Do Something vs LocalPlan Do Minimum, Morning (AM) Peak

Figure 10. 2031 Flow Differences, Broxbourne Do Something vsLocal Plan Do Minimum, Inter-Peak



Figure 11. 2031 Flow Differences, Broxbourne Do Something vsLocal Plan Do Minimum, Evening Peak



6.2.9 The modelling suggests the package of mitigation measures introduced into the Do Something scenario has a relatively localised effect. Figure 12shows the flow changes between the Do Minimum scenario and the Do Something scenario for the morning peak. A similar pattern is evident in theother time periods.

Figure 12: Countywide 2031 Flow Differences, Broxbourne Do Something vs Local Plan Do Minimum, Morning Peak



6.3 Stress Maps and Junction Delays

6.3.1 Figure 14, Figure 16 and Figure 18 show the link stress and average junction delay for the morningpeak, inter-peak and evening peak Do Something scenarios. The Do Minimum scenario figures havealso been repeated in Figure 13, Figure 15 and Figure 17 for ease of comparison between thescenarios.

6.3.2 The Broxbourne 2031 COMET Do Something scenario indicates the main impact of the mitigationmeasures in section 3 is along the A10 corridor. Delays identified at three out of four junctions alongthe A10 in section 5.2.3 have been reduced. The exception is the A10 / Park Plaza junction.

6.3.3 This 2031 Do Something scenario has not been optimised in terms of traffic signals, and as a result,various schemes which included the conversion from non-signalised roundabout into signalisedjunctions experience higher delays when compared with the Do Minimum scenario. These increasethe delays experienced by up to one minute. The junctions affected include the Fishpools junction(scheme 15), Goffs Lane/Newgatestreet Road / Cuffley Hill (scheme 16) and Church Lane schemes7 and 8. Delays in Brookfield are reduced due to the previous coding loading zones at a single pointon the network. As discussed earlier in the technical note, no signal optimisation was carried out inorder to retain consistency with the WYG modelling assumptions, in line with the brief



Figure 13. 2031 COMET Local Plan Do Minimum, V/C and JunctionDelays, Morning Peak

Figure 14. Broxbourne 2031 COMET Do Something, V/C andJunction Delays, Morning Peak



Figure 15. 2031 COMET Local Plan Do Minimum, V/C and JunctionDelays, Inter-Peak

Figure 16. Broxbourne 2031 COMET Do Something, V/C andJunction Delays, Inter-Peak



Figure 17. 2031 COMET Local Plan Do Minimum, V/C and JunctionDelays, Evening Peak

Figure 18. Broxbourne 2031 COMET Do Something, V/C andJunction Delays, Evening Peak



6.3.4 Table 2 shows the effects of the mitigation measures at four key junctions. These junctions havebeen selected based on the difference in performance as a result of the implemented mitigationmeasures. The Highway Scheme ID is consistent with the mitigation ID presented in Figure 5.

Table 2. Main Highway Schemes Comparison

Key Schemes Do Minimum Scenario Do Something Scenario

HighwaysScheme 3

Park PlazaNorth,

HamburgerRoundabout

V/C over 80% on allapproachesAverage delay of ~60seconds across all arms,with a delay of ~180seconds on the eastboundapproach.

V/C under 70% across thejunction.Delays are reduced acrossall arms, with eastboundapproach delay reduced to~25 seconds

HighwaysSchemes 5 &6

CollegeRoad/A10 and

ChurchLane/A10

Improvements

Delays of ~ 40 seconds inboth junctions, for morningand inter-peak. Delays ~60 seconds in PM peak atChurch Lane/A10 junctionand A10 northboundapproaches with V/C over90% for each period.

Delays have been reducedfor each time period to upto 20 secondsV/C under 60% for eacharm.

HighwaysScheme 15

Fishpoolsjunction

reconfiguration

~ Less than 20 seconds ofdelay on all approaches tothe junction

Increase in delays onnorthbound approach.Average junction delay upto ~120 seconds.Signal optimisation mayreduce the delays.

HighwaysScheme 16

Goffs Lanejunction

reconfiguration

Less than 10 seconds ofdelay across all arms

Increases in delays acrossall arms to between ~15and ~80 seconds. Signaloptimisation and flarescould potentially improvethe junction performance.

6.4 Modal Split Changes

6.4.1 The package of mitigation measures included a range of sustainable transport interventions acrossthe borough alongside the highway based interventions. Overall, the modelling suggests this has nosignificant net change in the modal splits for trips originating or ending in Broxbourne. Similarly tripsinternal to the Borough of Broxbourne have a small change in the modal splits.

6.4.2 Table 3, Table 4 and Table 5 show the modal splits for trips originating in Broxbourne, trips withdestinations in Broxbourne and trips that have both their origins and destination in Broxbournerespectively. The PT element refers to public transport, which includes both bus and rail, whilst theactive mode refers to walking and cycling.

Table 3. COMET Modal Splits for Trips with a Production in Broxbourne

Mode Do-Minimum Do-Something

Car 62.8% 63.1%

PT 5.9% 5.5%

Active 31.3% 31.4%



Table 4. COMET Modal Splits for Trips with an Attraction in Broxbourne


Car 63.0% 63.5%

PT 4.1% 3.5%

Active 32.9% 33.0%

Table 5. COMET Modal Splits for Trips with a Production and Attraction in Broxbourne


Car 55.2% 55.3%

PT 2.5% 2.5%

Active 42.3% 42.2%

6.4.3 The above tables show small changes in the overall modal splits across the whole day and reflectthe fact that there are highway interventions as well as public transport Improvements.



7. Summary

7.1.1 AECOM have undertaken and analysed two runs of the COMET model to assist BBC in thedevelopment of their transport strategy. This has required the testing of a range of mitigationmeasures defined by BBC and WYG as well as reviewing and revisiting planning data assumptions.

7.1.2 The package of mitigation options tested appears to have fairly localised effects on the network andthe proposed highway interventions, especially along the A10 do not appear to draw in demand fromthe wider strategic road network.

7.1.3 The package of mitigation schemes along the A10 has a positive effect on the delays at the keyjunctions along this corridor. Elsewhere, where delays do increase, these tend to be as a result ofsignalised junctions.

7.1.4 Away from the A10, in Broxbourne and Hoddesdon, some localised re-routeing is observed as aresult of the 20mph scheme along the A1170.

7.1.5 The sustainable transport interventions do not appear to have a significant impact on the modal splitof those travelling.

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