13 EFFECTS ON ALL TRAVELLERS - Planning Inspectorate · ENVIRONMENTAL STATEMENT CHAPTER 13 EFFECTS ON ALL TRAVELLERS MARCH 2015 PAGE 13-3 refers to 'new roads', it is considered that

HIGHWAYS AGENCY – M4 JUNCTIONS 3 TO 12 SMART MOTORWAY

ENVIRONMENTAL STATEMENT CHAPTER 13 EFFECTS ON ALL TRAVELLERS

MARCH 2015

PAGE 13-1

13 EFFECTS ON ALL TRAVELLERS

13.1 Introduction

13.1.1 The purpose of this chapter is to assess the potential effects of the

Scheme on vehicle travellers, as stipulated within Design Manual for

Roads and Bridges (“DMRB”), Volume 11, Section 3, Part 9, ‘Vehicle

Travellers’ (Ref 13-1); and for ‘Non-Motorised Users’ (“NMUs”)1, as

required by DMRB, Volume 11, Section 3, Part 8, ‘Pedestrians, Cyclists,

Equestrians and Community Effects’ (Ref 13-2).

13.1.2 As acknowledged in DMRB, the effects which are assessed are

qualitative, subjective assessments which cover the 'view from the road'

experienced by vehicle travellers and the potential for ‘driver stress’

caused by a number of factors, as described below.

13.1.3 NMUs, whilst not permitted to use motorways for safety reasons, may be

affected by the Scheme when travelling on the locally adopted highway

network and other Public Rights of Way (“PRoW”) surrounding or

interacting with the Scheme as shown on the Environmental Masterplan,

which can be found in Annex A of the Engineering and Design Report

(“EDR”) (Document Reference 7.4). These PRoW comprise footpaths and

bridleways, several of which cross the M4 on overbridges and

underbridges or via subways.

13.1.4 Due to the nature of the assessment of effects on all travellers, this

chapter reports the assessment as a Scheme wide assessment, rather

than on a link by link basis as with other chapters of this Environmental

Statement (“ES”). This chapter is structured under the following sections:

a) Methodology;

b) Baseline conditions;

c) Value (sensitivity) of resource;

d) Regulatory/policy framework;

e) Design, mitigation and enhancement measures, including

monitoring requirements;

f) Assessment of residual effects upon travellers;

1 DMRB Volume 11 Section 3, part 8 refers to NMUs in full as ‘pedestrians, cyclists, equestrians’ and

in short as ‘pedestrians and others’.



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g) Net effects of the Scheme on vehicle travellers in the Design Year

(2037);

h) Cumulative effects;

i) Limitations encountered in compiling the ES; and

j) Summary.

13.1.5 All drawings referenced within this chapter are presented in Document

Reference 6.2 (ES Figures), and all appendices referenced in this chapter

are presented in Document Reference 6.3 (ES Appendices).

13.2 Methodology

General approach

13.2.1 The methodology to assess the effects of the Scheme on all travellers is

qualitative, and taken from DMRB (Ref 13-1 and 13-2). The combined use

of these separate subject assessment frameworks is prescribed in Interim

Advice Note (“IAN”) 125/09 ‘Supplementary guidance for users of DMRB

Volume 11 ‘Environmental Assessment’’ (Ref 13-3), Section 2.2.

13.2.2 The assessments have also been undertaken in accordance with the

general principles and structure of assessment methodology contained

within DMRB Volume 11, Section 2, Part 5 HA 205/08 ‘Assessment and

Management of Environmental Effects’ (Ref 13-4), which has been

applied, as appropriate, and tailored to the context of the Scheme. These

include: the definition of assessment years and scenarios of assessment;

information assembly; identifying potential impacts, including permanent,

temporary and cumulative impacts; determining the significance of

environmental effects by combining the environmental value and

magnitude of impacts; determining the significance of cumulative effects;

and management of environmental effects.

Vehicle travellers

View from the road

13.2.3 Chapter 2 of DMRB Volume 11, Section 3, Part 9, entitled ‘View from the

Road’, suggests that benefits can be experienced by drivers as a result of

the construction of new roads in areas of ”high quality scenic landscapes”,

with “views ‘out from the road’ providing interest and helping to alleviate

driver stress.” Conversely, if a new road passes through heavily

industrialised or other visually unattractive areas, this can constitute an

adverse effect, and may cause an increase in driver stress. Whilst DMRB



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refers to 'new roads', it is considered that the principles can be applied

appropriately to improvements to existing roads, such as those proposed

as part of the Scheme.

13.2.4 Paragraph 2.6 of DMRB (Volume 11, Section 3, Part 9) allows schemes to

be placed in one of four categories as part of the subjective review: ‘no

view’ (the road is deep in a cutting); ‘restricted view’ (frequent cutting or

structures cutting the view); ‘intermittent view’ (road at ground level but

with shallow cuttings or barriers at intervals); and ‘open view’ (the view

extending over many miles). These categories have been determined to

provide an assessment of the surrounding landscape (the view beyond the

confines of the highway), not the road or roadside infrastructure itself

(gantries, bridges, signage), which only temporarily affects views.

13.2.5 As the M4 already exists and the Scheme provides only minor highway

alignment modifications, together with additional driver information,

reallocation of carriageway space and minor carriageway widening, it is

considered that the view from the M4 will not change materially as a result

of the Scheme. However, additional gantries that are necessary for the

information system signs will provide intermittent interruptions to the view,

albeit ones that are consistent with typical motorway infrastructure.

13.2.6 DMRB does not require an assessment of views from a road for vehicle

travellers on local roads. Views from side roads do not change in the same

way as views on the road being improved, as set out above, save for

glimpsed views and minor additional infrastructure on collector roads. The

‘view from the road’ assessment has therefore not been deemed

appropriate or applicable on local roads, and as such has been scoped out

of assessment in this chapter. However, an assessment of the effect of the

Scheme on visual amenity from local roads and PRoWs which interact

with the Scheme is included in chapter 8 Landscape.

Driver stress

13.2.7 Chapter 3 of DMRB Volume 11, Section 3, Part 9 is entitled ‘Driver Stress’,

and centres around the assessment of driver stress, which is defined as

“the adverse mental and physiological effects experienced by a driver

traversing a road network” (paragraph 3.1), which could be influenced by

factors such as “road layout and geometry, surface riding characteristics,

junction frequency, and speed and flow”. DMRB also notes that drivers will

select routes “which they believe to give the shortest reliable journey time,

taking account of expected variability” (paragraph 3.3). In combination,



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induced feelings of “discomfort, annoyance, frustration or fear, culminating

in physical and emotional tension” are said to potentially reduce the safety

of a journey. As such, the assessment of the effects of a scheme on driver

stress is an important part of the Environmental Impact Assessment

(“EIA”) process, requiring a qualitative and relative assessment between

the Do Something and Do Minimum options for the “worst year in the first

fifteen after opening”. In the case of the Scheme, this is taken as 2037 (the

‘Design Year’), as year on year traffic growth is assumed to occur.

13.2.8 It should be noted that despite the numerous elements contributing to

driver stress noted above, only speed and flow are used within the

assessment of driver stress under DMRB methodology.

13.2.9 The methodology and scenarios contained within the assessment are in

accordance with DMRB and are described below. These scenarios are

then subject to the analysis of driver stress.

13.2.10 DMRB suggests driver stress is comprised of three components:

a) Frustration, associated with a driver’s inability to drive at a

consistent speed, such as the speed limit (due to congestion), with

frustration increasing as traffic speeds fall, or at junctions and road

works. This could also apply to the journey time reliability

mentioned above, and the experience of drivers being caught in

severe congestion (such as gridlock caused by traffic flow

breakdown), etc;

b) Fear of potential accidents, which may be associated with the

presence and proximity of other vehicles, inadequate sight and

stopping distances, poor lighting, road works and poor surfacing,

with feelings compounded during adverse weather; and

c) Route uncertainty, primarily associated with inadequate signing and

information.

13.2.11 DMRB notes that the available research does not permit a detailed

assessment of driver stress, and instead the assessor should use a simple

three-point descriptive scale (low, moderate or high) to assess driver

stress, relatively comparing Do Something and Do Minimum options. It

also suggests that this should be applied to the ‘worst year’ in the first 15

years after opening.



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13.2.12 Table 13.1 reproduces the assessment framework for driver stress on

motorways from DMRB, with driver stress being considered to be a

function of purely average peak hourly flow per lane and average journey

speed. As noted above, no other elements which contribute to driver

stress, such as those mentioned in paragraph 13.2.10, are considered

within the assessment framework.

Table 13.1 Description of driver stress on motorways

Average peak hourly flow per lane (flow/hour)

Average journey speed (km/hr)

Under 75 75-95 Over 95

Under 1200 High Moderate Low

1200-1600 High Moderate Moderate

Over 1600 High High High

Source: DMRB, Volume 11, Section 3, Part 9

13.2.13 The simple and rigid framework summarised in the table equates slowing

speeds and increasing flow with elevated driver stress. In order to ensure

that the assessment of driver stress applied to the Scheme is appropriate,

assessors have had regard to the origin of the assessment methodology

and changes in circumstances in the intervening period.

13.2.14 The assessment methodology is based upon research from 19902 , at a

time when smart motorways had not yet been conceived in the United

Kingdom (Ref 13-5). Slower speeds and increased traffic flows are two

characteristics of smart motorways, which regulate (by reducing) traffic

speeds to prevent flow breakdown, which in turn increases total traffic

throughput thereby increasing flows. In the driver stress assessment, this

would result in an increase in driver stress.

13.2.15 However, since the development of DMRB methodology, understanding of

the principal factors which cause driver stress has developed, and

frustration at the inability to drive at a constant speed, as well as unreliable

journey times, are now considered to represent factors of increased

importance in assessing driver stress, both of which factors are addressed

by the introduction of a smart motorway.

2 Uncertainty and Driver Stress: A Review. Oxford University Transport Studies Unit: Bates, Davies, Goodwin,

Kenny, Parkes, Richardson, 1990.



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13.2.16 Similarly, the other known benefits which result from the introduction of

smart motorways, such as maintaining existing high safety standards, are

not factored into the assessment methodology for determining driver

stress. These benefits, which are discussed in DMRB (noted within

paragraph 13.2.10 above), but are excluded from the limited speed and

flow analysis assessment prescribed, are discussed in paragraphs 13.8.11

to 13.8.16 of this chapter.

13.2.17 In addition, journey time reliability, a factor considered to be extremely

important for both highway users and traffic managers3 in controlling

congestion and smoothing traffic flow (which could be said to reduce driver

stress), is omitted from the assessment methodology (Ref 13-6).

13.2.18 Consequently, this simple assessment methodology is not appropriate for

application to the Scheme. As such, the assessment of the effects of the

Scheme on drivers seeks to augment DMRB assessment methodology on

journey quality to address these omissions and develop understanding of

the effects of a smart motorway on driver stress. Professional judgement

is used where the assessment methodology has been augmented in this

way.

13.2.19 As noted above (paragraph 13.2.3), the assessment methodology in

DMRB focuses on the road being constructed or modified - the Scheme.

However, for a more robust assessment, distributor roads or roads

crossing the M4 within the Order limits, which may be used as alternative

routes during construction, or may have changes in traffic routeing as a

result of the operation of the Scheme, are also considered within this

assessment.

13.2.20 The assessment framework for driver stress on the non-motorway, local

road network, which consists of dual and single carriageways, is provided

in Tables 13.2 and 13.3. The roads that have been assessed on this basis

are presented in Tables 13.4 and 13.5.

3 http://www.tfl.gov.uk/cdn/static/cms/documents/technical-note-11-to-what-extent-is-congestion-and-

unreliability-on-the-road-network.pdf



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Table 13.2 Description of driver stress on dual-carriageway roads




Under 1200 High2 Moderate Low




2 ‘Moderate’ in urban areas.

Table 13.3 Description of driver stress on single-carriageway roads




Under 600 High2 Moderate Low




2 ‘Moderate’ in urban areas. Note: The figures given in the tables are considered to be for guidance only, and no similar tables are produced for roads operating under construction conditions. Using expert judgment they have been applied to the construction scenario for this assessment and this is explained below.

13.2.21 At this stage, the contractor, responsible for construction of the Scheme,

has not been appointed and, as such, it is not possible to provide detailed

information on the final construction and logistics plan, and therefore an

Outline Environmental Management Plan (“EMP”) has been developed to

accompany this ES (Appendix 4.2). An Outline Construction

Environmental Management Plan (“CEMP”) is contained in the Outline

EMP and will be finalised pursuant to a requirement attached to the DCO.



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13.2.22 However, support and construction advice has been sought from the

Agency contractors’ panel who have provided programme and

construction information. This advice has established traffic management

scenarios on which a simple assessment of the construction effects has

been developed. This is explained more fully below. The data used within

the assessments on driver stress, such as traffic flow (as Annual Average

Daily Traffic (“AADT”)), traffic speeds and the percentage of Heavy Goods

Vehicles (“HGVs”) are extracted from the Scheme traffic model.

13.2.23 DMRB stipulates that to establish the effect of the Scheme on driver

stress, the following assessment scenarios are required:

a) a base year - for the purposes of this assessment a 2013 base year

has been used, which is rebased to include traffic growth between

2009 and 2013 (2009 being the original base year, defined as the

year that traffic data were collected and traffic model construction

started);

b) a 2037 Do Minimum scenario - as noted above, DMRB requires a

scenario to be tested which is equivalent to the worst case year 15

years after scheme opening. As the Scheme is scheduled to be

operational in 2022, the Design Year for assessment purposes,

when traffic flows are at their highest, is assumed to be in 2037.

The 2037 Do Minimum scenario is equivalent to traffic conditions in

2037, which include traffic growth forecasts in accordance with

WebTAG, but assume the Scheme is not built;

c) 2037 Do Something - this scenario is the same as the Do Minimum

scenario in terms of traffic demand forecasts (i.e. traffic growth is

applied to 2037), but with the inclusion of the Scheme; and

d) in addition to these scenarios, a 2018 construction impact

assessment has been undertaken. 2018 was selected as this is

likely to be the time when traffic management has been introduced

to substantial portions of the Scheme to support the Scheme

construction works. This 2018 period4 is likely to have traffic

characteristics mid-way between the Do Minimum and Do

Something scenarios. In accordance with the EDR (Document

Reference 7.3), this assumes the Scheme is under construction (by

4 Traffic models exist for each year of the construction period years, with alternative construction sub-

options for each of these years. As the models each produce similar results, the mid-way point has been selected for reporting purposes and brevity.



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2018 the construction programme indicates part of the Scheme

between junction 8/9 and 12 is already open), and traffic

management will be in place with all running lanes operational with

narrower lanes and a reduced speed limit of 50 mph in place on the

eastern portion of the Scheme.

13.2.24 Unlike in other environmental assessment chapters of DMRB, such as

those prescribed in DMRB, Volume 11, Section 2, Part 5 (HA 205/08)

‘Assessment and Management of Environmental Effects’ (Ref 13-4),

where the ‘significance’ of environmental effects is scored using

‘significance criteria’ in a 25 point matrix containing a five-point

environmental value (sensitivity) score and a five-point magnitude of

impact (degree of change) score, none of the assessments contained

within the ‘vehicle traveller’ chapter of DMRB has assessment ‘significance

criteria’. However, given the simplistic nature of DMRB assessment

methodology, this affords the opportunity to adapt and augment the driver

stress and journey quality scoring framework, without deviating from the

overall approach.

13.2.25 The relative assessment methodology defined within DMRB requires the

comparison of the change in circumstances for the Do Minimum and Do

Something options for the Design Year (2037). These scenarios have

therefore been compared within the analysis, and the ‘net effects’ of

change (attributable to the Scheme) have been presented. This has also

been undertaken for construction effects in 2018 as noted above. The

baseline traffic conditions for driver stress in 2013 are also presented. The

qualitative, comparative outputs are presented as changes which are

classified as neutral, beneficial or adverse. The ‘magnitude of impact’ is

classified as major, moderate, minor, negligible, or no change in

accordance with Table 2.2 of DMRB, Volume 11, Section 2, Part 5, 205/08

(Ref 13-4), which is reproduced in Appendix 13.1.

13.2.26 The augmented methodology on journey quality proposed here, in addition

to using DMRB speed and flow tables for each free running stretch of the

Scheme, and for each of the local roads, introduces the ‘missing factors’

referred to above. These are:

a) journey time reliability;

b) road surfacing;

c) road layout and geometry;

d) junction frequency;



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e) safety;

f) driver information; and

g) reduction of general congestion and likelihood of ‘traffic flow

breakdown’.

13.2.27 These are scored as beneficial, neutral or adverse for the entire Scheme,

rather than for each link, and assigned a ‘magnitude of impact’ of major,

moderate, minor, negligible, or no change, comparing the Do Minimum

and Do Something scenarios.

Non-motorised users

13.2.28 The assessment of the Scheme effects on pedestrians, cyclists and

equestrians - NMUs - is focussed on the impact on the PRoW.

13.2.29 For NMUs the sensitivity, magnitude of impact and significance of effects

have been assessed in accordance DMRB Volume 11, Section 2, Part 5,

HA 205/08 (Ref 13-4), summary tables of which are provided in Appendix

13.1.

Study area

13.2.30 Following DMRB, the study area for the assessment of all travellers is the

M4 junctions 3 to 12. However, for robustness, consideration has also

been given to roads outside of this study area, which may be affected by

traffic re-assignment as a result of the Scheme during construction and

operation. Primarily, these affected roads are M4 distributor roads, and

roads that pass over, beneath or parallel to the M4 (which could be used

as alternative routes). The roads that are included within this assessment

are summarised within Tables 13.4 and 13.5.

Table 13.4 Roads potentially affected by the Scheme (M4 approaches)

M4junction Route

j12 A4W towards Theale A4W towards Calcot j12 A4E from Theale A4E from Calcot j11 A33S towards Three Mile Cross A33S towards Reading j11 A33N from Three Mile Cross A33N from Reading j11 A33S towards Basingstoke B3270E towards Whitley Wood j11 A33N from Basingstoke B3270W from Whitley Wood

j10 A329MS towards Bracknell A329MN towards Winnersh j10 A329MN from Bracknell A329MS from Winnersh j8/9 A308ME towards Maidenhead A404N towards Bisham j8/9 A308MW from Maidenhead A404S from Bisham j7 M4 Spur towards Slough A4W towards Slough



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M4junction Route

j7 M4 Spur from Slough A4E from Slough j6 A355N towards Slough A355S from Slough

j6 A355N from Windsor A4W towards Slough j6 A355S towards Windsor A4E from Slough j5 B470W towards Datchet B470E from Datchet j5 A4E towards Heathrow A4W from Heathrow

j4b M25A north of junction M25C north of junction j4b M25A south of junction M25C south of junction

j4 M4 Spur towards Heathrow A408N towards Uxbridge j4 M4 Spur from Heathrow A408S from Uxbridge j3 A312S towards Heathrow A312N towards Southall j3 A312N from Heathrow A312S from Southall

Table 13.5 Roads potentially affected by the Scheme (A4 and crossing roads)

M4 junction

A4 links

j12 A4E towards Reading A4W from Reading j10 A4W towards Reading A4E from Reading

j10 to j8/9 A4W towards Reading A4E from Reading j8/9 A4W towards Maidenhead A4E from Maidenhead

j7 A4E from Maidenhead A4W towards Maidenhead j5 A4W towards Slough A4E from Slough j3 A312S towards Heathrow A312N from Heathrow j3 A4E towards Heathrow A4W from Heathrow

13.3 Baseline conditions

Vehicle travellers

Driver stress

13.3.1 A summary of average peak hourly flow per lane, average journey speed

and percentage of HGVs, is presented within Table 13.6 (eastbound

traffic) and Table 13.7 (westbound traffic) for the baseline year (2013), for

the mainline M4 carriageway, for the connected road network and for

roads that pass over, under or parallel to the Scheme5. The percentage of

HGVs is weighted by a factor of 3 in comparison to cars when calculating

the average peak hourly flow per lane, to take into account the size of the

vehicles in comparison to a car (this approach is specified within DMRB

and also standard methodology used when analysing vehicle ‘flow units’).

5 Entry and exit slips have not been considered as they would not align with the rigid speed and flow

tables provided in DMRB assessment framework due to the presence and close proximity of junctions, and short link lengths slowing speeds. The tables are designed for free flow sections of the link, not short motorway slips.



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Table 13.6 Existing estimated driver stress for drivers on the eastbound M4 carriageway for 2013 (base year)

M4 junctions

Link

2013 Base

Average peak hourly flow per lane (flow units/hr)

Average journey speed

(km/hr)

Average HGVs

(%)

Driver stress level

12-11 Mainline 1998 88 6.7% High

11-10 Mainline 2025 87 6.9% High

10-8/9 Mainline 1930 89 6.2% High

8/9-7 Mainline 2026 87 6.0% High

7-6 Mainline 1947 87 6.8% High


5-4b Mainline 1612 93 6.6% High

4b-4 Mainline 1672 83 4.8% High


13.3.2 All of the M4 links assessed are categorised as contributing to high levels

of driver stress in the base year in the eastbound direction.

Table 13.7 Existing estimated driver stress for drivers on the westbound M4 carriageway for 2013 (base year)

M4 junctions

Link

2013 Base

Average peak hourly flow per lane (flow units/hr)


(km/hr)

Average HGVs

(%)

Driver stress level

12-11 Mainline 1746 94 6.5% High

11-10 Mainline 1860 91 6.0% High

10-8/9 Mainline 1776 93 5.8% High

8/9-7 Mainline 1866 91 5.8% High






13.3.3 All of the westbound M4 links are categorised as contributing to high levels

of driver stress in the base year in the westbound direction.

13.3.4 A similar analysis has been performed on the local, connected or affected

roads in Table 13.8 using data taken from the strategic traffic model.



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Table 13.8 Existing estimated driver stress for drivers on non-motorway local, connected or affected roads – M4 approaches 2013 (base year)

M4 junction

Junction approach link

2013 Base

Average peak hourly flow

per lane (flow units/hr)


Average HGVs (%)

Driver stress level

12

A4W towards Theale 906 30 6.9% High

A4E from Theale 865 98 11.1% Low

A4W towards Calcot 768 24 2.6% Moderate

A4E from Calcot 852 64 1.1% Moderate

11

A33N from Basingstoke 745 99 4.5% Low

A33S towards Basingstoke 829 87 4.9% Low

A33N from Three Mile Cross 770 64 6.0% Moderate

A33S towards Three Mile Cross 731 52 5.8% Moderate

A33N approach from Reading 336 15 4.8% Moderate

A33S towards Reading 532 39 3.5% Moderate

B3270W from Whitley Wood 836 61 1.4% High

B3270E towards Whitley Wood 915 61 1.3% High

10

A329MN towards Winnersh 1236 96 2.0% Moderate

A329MS from Winnersh 1173 97 2.0% Low

A33N from Bracknell 1869 82 2.6% High

A33S towards Bracknell 1726 86 3.1% High

8/9

A404N towards Bisham 1284 97 4.3% Moderate

A404S approach from Bisham 1481 93 3.5% Moderate

A308MN towards Maidenhead 707 103 3.2% Low

A308MS from Maidenhead 579 13 4.0% High

7 M4 Spur towards Slough 825 51 3.3% High

M4 Spur from Slough 757 103 5.1% Low

6

A355N towards Slough 1015 40 3.5% High

A355S approach from Slough 1047 95 5.1% Low

A355N from Windsor 503 90 1.1% Low

A355S towards Windsor 530 88 4.6% Low

5

A4W towards Slough 549 64 4.7% Moderate

A4E from Slough 478 64 7.4% Moderate

A4W from Heathrow 1087 63 6.3% High

A4E towards Heathrow 1092 63 7.4% High

B470W towards Datchet 539 62 2.4% Moderate

B470E from Datchet 467 62 1.7% Moderate

4b

M25C north of junction 1959 88 8.7% High

M25A north of junction 2171 78 8.3% High

M25C south of junction 1413 98 7.7% Moderate

M25A south of junction 1523 94 7.7% Moderate

4

M4 Spur towards Heathrow 774 78 4.3% Moderate

M4 Spur from Heathrow 652 79 3.6% Moderate

A408N towards Uxbridge 465 19 3.9% High

A408S from Uxbridge 653 42 7.3% High



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M4 junction

Junction approach link

2013 Base

Average peak hourly flow

per lane (flow units/hr)


Average HGVs (%)

Driver stress level

3

A312N towards Southall 1022 46 5.7% Moderate

A312S from Southall 1070 45 6.9% Moderate

A312N from Heathrow 1048 45 3.5% Moderate

A312S towards Heathrow 989 33 5.0% Moderate

Table 13.9 Existing estimated driver stress for drivers on non-motorway local, connected or affected roads – A4 links 2013 (base year)

M4 section

Parallel A4 link

2013 Base

Average peak hourly flow per

lane

(flow units/hr)


(Km/hr)

Average HGVs

(%)

Driver stress level

12-11 A4W (M4J12 to Reading) 520 60 4.6% Moderate

A4E (Reading to M4J12) 655 59 5.7% Moderate

11-10

A4W (Reading to A3290 Woodley)

907 45 2.9% Moderate

A4E (A3290 Woodley to Reading)

1147 37 3.9% High

10-8/9

A4W (A3290 Woodley to Maidenhead)

970 74 1.4% High

A4E (Maidenhead to A3290 Woodley)

1245 56 0.9% High

8/9-7

A4W (Maidenhead to Cippenham)


A4E (Cippenham to Maidenhead)


7-6 A4W (Cippenham to Slough) 282 36 2.7% Moderate

A4E (Slough to Cippenham) 363 57 3.3% Moderate

6-5 A4W (Slough to M4J5) 825 34 3.4% High

A4E (M4J5 to Slough) 699 38 5.6% High

5-4b A4W (M4J5 to A3044 Longford) 811 73 4.6% High

A4E (A3044 Longford to M4J5) 775 78 6.8% Moderate

4b-4

A4W (A3044 Longford to Heathrow)


A4E (Heathrow to A3044 Longford)


4-3 A4W (Heathrow to Cranford) 991 44 14.4% High

A4E (Cranford to Heathrow) 950 44 15.4% High



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Table 13.10 Existing estimated driver stress for drivers on non-motorway local, connected or affected roads – M4 crossing roads 2013 (base year)

M4 section

M4 crossing link

2013 Base


lane (flow units/hr)


Average HGVs (%)

Driver stress level

12-11 Burghfield Ln N from Burghfield 586 82 3.5% Low

Burghfield Ln S towards Burghfield


11-10

A327N south of B3270 from Shinfield

1134 62 1.0% High

A327S south of B3270 towards Shinfield

1127 62 1.0% High

Mill Ln N towards Earley 323 55 2.3% Moderate

Mill Ln S from Earley 515 58 1.1% Moderate

B3030N towards Winnersh 392 43 0.9% Moderate

B3030S from Winnersh 308 34 0.6% Moderate

A329N towards Reading 714 57 1.5% Moderate

A329S from Reading 841 53 1.3% High

10-8/9

A321N from Wokingham 492 84 1.4% Low

A321S towards Wokingham 476 82 1.3% Low

The Straightmile N from Wokingham


The Straightmile S towards Wokingham

346 71 1.1% Low

B3018N from Binfield 119 72 2.3% Low

B3018S towards Binfield 210 74 0.6% Low

B3024N from Windsor 352 43 1.6% Moderate

B3024N towards Windsor 395 43 5.0% Moderate

8/9-7

A330N towards Maidenhead 746 35 1.5% High

A308S from Maidenhead 844 33 3.6% High

A308N towards Maidenhead 531 34 2.7% Moderate

A308S from Maidenhead 884 20 4.7% High

Marsh Ln N towards Taplow 10 47 0.0% High

Marsh Ln S from Taplow 119 60 1.8% Moderate

B3026N towards Slough 235 43 3.4% Moderate

B3026S from Slough 164 44 2.8% Moderate

6-5

A332N crossing M4 towards Slough


A332S crossing M4 from Slough 496 48 3.3% Moderate

B376N crossing M4 towards Slough

441 73 2.1% Low

B376S crossing M4 from Slough 554 73 2.6% Low

Riding Court Rd N from Datchet 123 75 0.9% Low

Riding Court Rd S towards Datchet


5-4b Sutton Ln N towards Langley 568 51 3.7% Moderate

Sutton Ln S from Langley 592 51 4.2% Moderate



MARCH 2015

PAGE 13-16

M4 section

M4 crossing link

2013 Base




Average HGVs (%)

Driver stress level

4b-4

Harmondsworth Rd N from Heathrow

388 38 11.7% Moderate

Harmondsworth Rd S towards Heathrow

478 30 13.1% Moderate

A408W towards Heathrow 828 44 5.1% High

A408E from Heathrow 950 82 8.0% High

4-3 A437N from Heathrow 560 40 7.8% Moderate

A437S towards Heathrow 780 35 5.8% High

13.3.5 As the connected or crossing road network is comprised of numerous

different roads types, with varying travel patterns and characteristics, there

is no common pattern of driver stress in the base year.

Non-motorised users

13.3.6 There is a network of PRoWs in the study area, several of which pass

close to and/or cross the M4 (see Drawing 8.2).

13.3.7 There are approximately 113 structures within the scope of the Scheme.

These include all overbridges, underbridges, pedestrian only underpasses,

subways and culverts which carry vehicular and/or NMUs across the M4.

However, not all of these structures will be altered or otherwise affected,

such that their use by NMUs requires assessment. The main effects for

NMUs concern the closure of four bridges for online replacement. These

are at Marsh Lane, Oldway Lane, Recreation Ground and Old Slade Lane.

13.4 Value (sensitivity) of resource

Vehicle travellers

13.4.1 For driver stress, relative levels of sensitivity have not been assigned to

the receptors (vehicle travellers), as DMRB does not provide, or require

the application of, any significance criteria (as noted within paragraph

13.2.24). However, a selection of qualitative assessment criteria is

available in TAG (Ref 13-7) (Unit A4.1, chapter 6) within the section

covering journey quality impacts. For driver stress, the assessment

requires a consideration of the three factors of frustration, fear of potential

accidents and route uncertainty, and a determination as to whether, on

balance, the effect is adverse or beneficial. The following guidance is then

provided to provide an assessment of the scale of effect:



MARCH 2015

PAGE 13-17

a) the assessment is likely to be slight when the number of travellers

affected is low (for example, less than 500 a day);

b) the assessment is likely to be large where the number of travellers

affected is high (for example, more than 10,000); and

c) the assessment is likely to be moderate in all other cases.

Non-motorised users

13.4.2 The majority of users (the receptor) of PRoWs (the facility) are assumed to

have low sensitivity (i.e. due to their local scale6). The main exceptions

concern the Thames Path, National Cycle Network Route 4 ("NCN4") and

Route 61 (“NCN61”), each of which has national significance and

accordingly is afforded high sensitivity. The environmental value (or

sensitivity) categories are summarised within Appendix 13.1. The

sensitivity of road crossing points (overbridges and underbridges), which

are not definitive PRoWs, is considered to be low in respect of change

(again, given their local scale and also the fact that the Scheme is not

changing significantly from Do Minimum to Do Something, i.e. the M4

already exists and crossings will be maintained). It is acknowledged there

will be some temporary severance during construction of the Scheme

associated with bridge construction at Marsh Lane, Oldway Lane,

Recreation Ground and Old Slade Lane. However, this severance will be

of a short-term duration, between 9 and 12 months, and there will be no

permanent severance as a result of the Scheme.

13.5 Regulatory/policy framework

13.5.1 A summary of the principal legislation and policy that has been considered

as part of this assessment is provided in Table 13.11.

6 The description and scale of assigning sensitivity within DMRB (Volume 11, Section 2, Part 5, HA

205/08) is relatively vague – so as to be broad enough to be applicable to a range of environmental assessment disciplines (such as air quality and noise). Scores range from very high (high importance, or rarity, or international scale) down to very low (low importance, rarity and local scale).



MARCH 2015

PAGE 13-18

Table 13.11 Regulatory and policy framework for all travellers

Policy/Legislation Summary of requirements Scheme response

Countryside and Rights of Way Act 2000 (as

amended) (Ref 13-8)

The Act improves the rights of way legislation by encouraging the creation of new routes and clarifying uncertainties about existing rights.

All PRoWs affected by the Scheme have been assessed.

National Planning Policy Framework 2012

(Ref 13-9)

Planning policies aim to protect and enhance PRoWs and access.

Local authorities should seek opportunities to provide better facilities for users, for example by adding links to existing rights of way networks including National Trails.

All PRoWs affected by the Scheme have been assessed.

National Planning Policy Guidance:

Environmental Impact Assessment (Ref 13-10)

As above. All PRoWs affected by the Scheme have been assessed.

National Networks National Policy

Statement December 2014

(Ref 13-11)

Requirement for Environmental Impact Assessment to assess effects on human beings (including effects on health).

Driver Stress assessment undertaken.

National Networks National Policy

Statement December 2014

(Ref 13-11)

Requirement for applicants to consider effects on the landscape during construction and operation, including effects on local amenity.

Effects on amenity of PRoWs assessed.



MARCH 2015

PAGE 13-19

Policy/Legislation Summary of requirements Scheme response

Requirement to consider reasonable opportunities to support other transport modes, including reasonable endeavours to address any existing severance issues that act as a barrier to NMUs.

Consideration of needs of pedestrians, cyclists and equestrians during the construction and operation phases.

Government expectation for use of reasonable endeavours to address the needs of cyclists and pedestrians in the design of new schemes.

Consideration of needs of pedestrians, cyclists and equestrians during the construction and operation phases.

13.6 Design, mitigation and enhancement measures, including monitoring requirements

Construction

13.6.1 Proposed mitigation measures during the construction phase will be

managed and monitored as part of the CEMP, which is to be secured by a

requirement attached to the DCO.

13.6.2 As set out in chapter 3 ‘Design Iterations and Alternatives Considered’, the

most appropriate construction methodology for the required improvements

to structures, such as overbridges and underbridges, has been selected

based on the particular circumstances applying in relation to each

structure, such as the availability of diversion routes, and the existence of

sensitive receptors in the vicinity of the structure. The alternatives

considered and the method of construction selected are set out in the

EDR.

13.6.3 Traffic management on the M4 will be in place during the phased

construction period with clear and appropriate signage provided for

alternative routeing. Three narrower lanes will be maintained in each

direction during peak times, with a reduced speed limit of 50 mph in place.

A 24-hour recovery service will be provided over the complete length of

the section of M4 under traffic management. Further details are set out in

the Outline Construction Traffic Management Plan ("CTMP"), which is

appended to the Outline CEMP (Appendix 4.2).



MARCH 2015

PAGE 13-20

13.6.4 Temporary road/PRoW closures will be required at overbridges, which are

to be increased in span to accommodate the Scheme. Careful phasing

and on-site management will be controlled through the CEMP to ensure

that disruption and the duration of PRoW closure are kept to a minimum.

13.6.5 During the construction period multiple bridges may be shut at the same

time where the closure of one bridge has no effect on another. Bridge

works at each location will take between 12 and 24 months, but this would

be concurrent with other bridge locations. More detailed information on the

works to be carried out to the structures along the Scheme and the

expected construction period for those works is provided in chapter 4

‘Scheme Description’ and summarised in Tables 13.18 and 13.19.

13.6.6 Where one bridge will be required to act as a diversion route during the

closure of another, these will be replaced sequentially. Overnight closure

of the whole M4 carriageway, eastbound and westbound, will be

necessary at certain times to accommodate demolition and construction

works on the overbridges. All side road crossings of the M4 will be

reinstated such that the long term effects on NMUs will be neutral. The

operational effects of the Scheme are beneficial and mitigation for effects

on travellers during the operational phase of the Scheme is not required.



MARCH 2015

PAGE 13-21

13.7 Assessment of residual effects

Construction

Vehicle travellers

Driver stress

13.7.1 An indicative assessment of construction effects has been undertaken.

Tables 13.12 and 13.13 show the 2018 construction year stress levels by

link for the eastbound and westbound journeys for the Do Minimum and

Do Something scenarios (i.e. without and with the Scheme). The net

effects of the change are presented in Table 13.14.

Table 13.12 Predicted driver stress experienced by eastbound M4 drivers for the construction assessment year –Do Minimum 2018

M4 junction

Link

2018 Do Minimum




(km/hr)

Average HGVs

(%)

Driver stress level

12-11 Mainline 2085 86 6.6% High

11-10 Mainline 2164 84 6.4% High

10-8/9 Mainline 1956 89 5.8% High

8/9-7 Mainline 2032 87 5.6% High






Table 13.13 Predicted driver stress experienced by eastbound M4 drivers for the construction assessment year –Do Something 2018

M4 junctions

Link

2018 Do Something




(km/hr)

Average HGVs (%)

Driver stress level

12-11 Mainline 1599 97 6.4% Moderate

11-10 Mainline 1726 94 6.0% High

10-8/9 Mainline 1461 100 5.7% Moderate

8/9-7 Mainline 1804 53 5.9% High



5-4b Mainline 1356 63 4.9% Moderate





MARCH 2015

PAGE 13-22

Table 13.14 Net effect of driver stress for eastbound M4 traffic associated with construction impact 2018

M4 junctions

Link

Driver stress level

2018 Do Minimum

2018 Do Something

2018 Do Something vs Do

Minimum

12-11 Mainline High Moderate +

11-10 Mainline High High 0

10-8/9 Mainline High Moderate +

8/9-7 Mainline High High 0



5-4b Mainline High Moderate +

4b-4 Mainline High High 0


Net Effect +3

13.7.2 The tables indicate the net effect on driver stress during construction is

predicted to be beneficial, which is counter intuitive and not likely to record

a correct assessment. The result is the outcome of the application of

DMRB, which has not been designed for assessing construction effects.

Nevertheless, a beneficial result will be obtained as traffic flows drop (as

noted in paragraph 13.2.14), which is associated with the reduction of

motorway capacity resulting from a 50 mph speed restriction. Using

DMRB, this yields a positive result. However, in practice, the principle set

out in DMRB, that drivers become more frustrated by not being able to

travel at the normal (as opposed to temporary) motorway speed limit,

would suggest that drivers would become more frustrated by roadworks

and traffic management. As set out at paragraph 13.2.10 (b), fear of

potential accidents associated with road works will be a factor adversely

affecting driver stress. The limitation of the methodology being applied to

construction effects is therefore noted and an adverse effect is predicted

using professional judgement.

13.7.3 A similar analysis is presented for the westbound travelling traffic in Tables

13.15, 13.16 and 13.17.



MARCH 2015

PAGE 13-23

Table 13.15 Predicted driver stress experienced by westbound M4 drivers for the construction assessment year –Do Minimum 2018

M4 junctions

Link

2018 Do Minimum




Average HGVs

(%)

Driver stress level

12-11 Mainline 1825 92 6.4% High

11-10 Mainline 1926 90 5.9% High

10-8/9 Mainline 1865 91 5.5% High

8/9-7 Mainline 1937 89 5.6% High






Table 13.16 Predicted driver stress experienced by westbound M4 drivers for the construction assessment year – Do Something 2018

M4 junctions

Link

2018 Do Something




Average HGVs

(%)

Driver stress level



10-8/9 Mainline 1375 101 5.3% Moderate

8/9-7 Mainline 1711 55 5.3% High



5-4b Mainline 1408 61 5.0% Moderate





MARCH 2015

PAGE 13-24

Table 13.17 Net effect of driver stress for westbound M4 traffic associated with construction impact 2018

M4 Sections

Link

Driver Stress Level

2018 Do Minimum

2018 Do Something

2018 Do Something vs Do

Minimum



10-8/9 Mainline High Moderate +




5-4b Mainline High Moderate +

4b-4 Mainline High High 0


Net Effect +4

13.7.4 As with the eastbound analysis, a beneficial effect is reported by

application of DMRB, which is counter intuitive. Again, this is because

DMRB has not been designed to assess construction effects and an

adverse effect is predicted, based on professional judgment for the

reasons given above.

13.7.5 In conclusion and notwithstanding the results of the construction impact

assessment presented in this section, there is the potential that the stress

levels for drivers using this part of the M4 during the construction period

will be temporarily elevated, in comparison to the existing levels. This is

due to traffic management measures including the use of narrow lanes

and reduced lane speeds, leading to temporary increases in journey times

and congestion. The lower speeds, greater frustration, possible delay and

queuing could further exacerbate the levels of stress currently experienced

by vehicle travellers. On the basis that only 3 out of 9 links eastbound and

4 out of 9 links westbound have shown changes in assessed levels of

driver stress and each of these changes is only by a single step in

magnitude, the overall magnitude of change is assessed as minor.

13.7.6 Other non-motorway links which could be affected by the introduction of

the Scheme, such as the network of roads feeding the M4, or any other

roads passing under or over or parallel to the M4 (summarised in Tables

13.4 and 13.5), which could be used as alternative routes during

construction, have been considered within the assessment. However, as

full construction and logistics information related to the Scheme is not yet

available, an indicative construction assessment has been undertaken.



MARCH 2015

PAGE 13-25

13.7.7 During the construction period, four of the overbridges across the M4 will

be closed while a replacement structure is constructed. Table 13.18

provides a list of these bridges together with the nominal duration of

closure from the time demolition of the existing structure commences until

the replacement bridge is open to traffic. In addition to the impact on local

traffic whilst the diversion is in place, disruption to traffic on the M4 will

occur at intermittent periods during demolition of the existing structure and

placement of the replacement bridge deck.

Table 13.18 Construction bridge closures

Overbridge Location Indicative programme Diversion route

Marsh Lane J8/9 – J7 Nov 2018 to Dec 2019 Bath Road (A4) and Lake End Road

Oldway Lane J7 – J6 Nov 2018 to Aug 2019

Using existing public rights of way and Wood Lane overbridge to cross M4

Recreation Ground J6 – J5 Mar 2018 to Nov 2018 Datchet Road and Upton Court Road

Old Slade Lane J5 – J4b Nov 2017 to Dec 2018 Colnbrook Bypass/Sutton Lane and North Park

13.7.8 The other bridges being replaced will in each case remain open until

completion of the replacement structure, at which time traffic will be

diverted to the new bridge and the old bridge demolished. Disruption to

traffic on the M4 will occur at intermittent periods during placement of the

replacement bridge deck and demolition of the existing structure. Table

13.19 provides a list of these bridges. All timescales are based on the

indicative construction programme and are subject to revision by the

appointed contractor.



MARCH 2015

PAGE 13-26

Table 13.19 Bridges remaining open until replacement bridge is constructed

Overbridge Location Indicative programme Traffic management

Ascot Road J8/9 – J7 Dec. 2017 to June

2019

Signal controlled, alternating, one-way traffic (“shuttle way working”) for tie-in and overlapping works

Monkey Island Lane J8/9 – J7 Oct. 2017 to Nov. 2018

Shuttle way working using signal control for tie-in and overlapping works

Lake End Road J8/9 – J7 Feb. 2018 to Mar. 2019


Huntercombe Spur J7 Sept. 2017 to Oct. 2019 Shuttle way working and phased construction

Wood Lane J7 – J6 Oct. 2017 to Aug. 2019


Datchet Road J6 – J5 March 2018 to July

2019


Riding Court Road J6 – J5 Nov. 2018 to Nov. 2019


13.7.9 The underbridges listed in Table 13.20 are to be lengthened during which

three narrower lanes will be generally maintained in each direction during

peak times, with a reduced speed limit of 50mph in place.

Table 13.20 Underbridges to be lengthened

Structure Duration of works

Thames Bray underbridge 27 months

Windsor Branch Railway underbridge 18 months

Langley Interchange underbridges 10 months



MARCH 2015

PAGE 13-27

13.7.10 In addition, the following culverts are to be widened (with minimal

disruption to traffic):

a) Ashley Arch culvert;

b) Sipson Subway; and

c) Two service culverts.

13.7.11 This will result in temporary road closure and diversion of vehicular and

NMU traffic. The construction programme will be developed so that when

overbridge crossings are closed, the diversion lengths and adverse

impacts will be kept to a minimum.

13.7.12 During the construction period, the three underbridges (referred to in Table

13.20) and the subway and culverts will be extended, with possible

temporary closure required for underbridge works.

13.7.13 Users of walking and cycling routes in the vicinity of the Scheme may

experience adverse effects as a result of the construction works. However,

appropriate mitigation measures (e.g. diversion routes, signage and

information to be provided to nearby residents prior to rebuilding) will be

implemented by the Contractor as set out in the Outline CEMP and Outline

CTMP (Appendix 4.2).

13.7.14 The effects on NMUs are discussed in the next section. Where journey

times are quoted, they are on the basis of the following speeds prescribed

in DMRB: 5kph on foot, 10kph for horses and 20kph for cyclists. It should

be noted that pedestrians in vulnerable user groups (i.e. elderly, disabled

and children) have an assumed walking speed of 3kph.

Non-motorised users

Journey times and travel patterns

13.7.15 To provide a basis for the assessment of the effect of the proposed bridge

works on NMUs, and in particular those bridges where online construction

with associated diversions of PRoWs is proposed, reference has been

made to DMRB (Ref 13-2, Chapter 6 – New Severance). In the absence

of appropriate survey data, it is not possible at this stage to directly

quantify the number of people whose journey will be affected in each case.

However, it is proposed to undertake surveys at an appropriate time of

year to confirm the assessment. In the meantime, DMRB does provide

guidance on the application of a three-point scale of slight, moderate or

severe in relation to the expected increase in journey distance that people

are likely to incur, as follows:



MARCH 2015

PAGE 13-28

a) slight – journeys will be increased by up to 250m;

b) moderate – journeys will be increased by 250 – 500m; or

c) severe – an increase in length of journeys of over 500m.

13.7.16 Marsh Lane overbridge connects Bath Road to the north with the villages

of Dorney, Eton Wick and Eton to the south of the M4. The route also

provides access to Dorney Lake. Marsh Lane overbridge is proposed to be

constructed online. During construction works on Marsh Lane overbridge,

which are anticipated to take 12 months, a diversion route will be available

via Lake End Road.

13.7.17 Lake End Road provides a suitable diversion route for Marsh Lane, as it

connects Bath Road to the north of the M4 with the villages of Dorney,

Eton Wick and Eton to the south of the motorway. Lake End Road

overbridge itself is proposed to be constructed offline to maintain suitable

access to Dorney Lake and Dorney School.

13.7.18 Lake End Road is just over 1km to the east of Marsh Lane and is reached

by diversion routes of 1.7km (20 minutes on foot, 10 minutes on horseback

and 5 minutes by cycle) on the south side and 3.5km (42 minutes on foot,

21 minutes on horseback and 10 minutes by cycle) on the north side. As

such, users of Marsh Lane overbridge may experience lengthened journey

times during the construction period which, based on the above criteria,

would be rated as severe. In response to concerns raised during the

Public Consultation exercise in November 2014, further consideration has

been given to appropriate alternative mitigation measures to address

these concerns. Two options have been identified which are the provision

of a temporary pedestrian access or the provision of a shuttle-bus service

for pupils residing to the north of the motorway, the latter providing the

most flexible and effective option.

13.7.19 Oldway Lane overbridge is used by pedestrians, cyclists and equestrians

to link residential areas on the outskirts of Slough (notably the Cippenham

area) with recreational activities along the Jubilee River. The Jubilee River

Cycle Path and walking routes pass along the towpath of the river and

provide links with Dorney Lake, NCN4 and the Thames Path. Oldway Lane

overbridge will be constructed online, as such the construction works could

have an adverse effect on recreational users in the short-term, as the

crossing would be temporarily severed during reconstruction of the

pedestrian bridge, which is anticipated to take 10 months. Alternative

access could be provided for the residents of Cippenham to the Jubilee



MARCH 2015

PAGE 13-29

River via Wood Lane overbridge. This would require a deviation of 1.1km

(13 minutes on foot, 7 minutes on horseback and 3 minutes by cycle)

between the bridges using existing rights of way or a total round trip of just

over 2km (26 minutes on foot, 13 minutes on horseback and 6 minutes by

cycle). Based on the criteria in paragraph 13.7.15, the severance incurred

during the reconstruction period would be adjudged as severe.

13.7.20 Recreation Ground overbridge provides a pedestrian and cycle link from

Datchet Road to the Upton Park area. It also provides properties in the

Upton Court Road area with the opportunity to link in with the wider Jubilee

River walking and cycling network. As the overbridge will be rebuilt online,

the walking/cycling route north to Upton Park Road may be affected by

construction works, which are anticipated to take 8 months to complete. A

diversion route is proposed via Datchet Road bridge. The Recreation

Ground and Datchet Road bridges are only some 350m apart, but the full

diversion route involves a distance of 1.9km (23 minutes on foot, 12

minutes on horseback and 6 minutes by cycle). Based on the criteria in

paragraph 13.7.15, the severance incurred during the reconstruction

period would be adjudged as severe.

13.7.21 Old Slade Lane overbridge is proposed to be rebuilt online, over the

course of approximately 12 months. The overbridge carries an

accommodation track over the M4 to provide access for farm use, local

pedestrians, dog walkers and cyclists as part of the Colne Valley Trail.

During the course of construction, an alternative access could be provided

from the Colnbrook Bypass to the south. However, this would result in

significantly lengthened journey times. The two bridges are just under 2km

apart and the diversion routes between the two are 3.1km (38 minutes on

foot, 19 minutes on horseback and 10 minutes by cycle) on the north side

and 4km (48 minutes on foot, 24 minutes on horseback and 12 minutes by

cycle) on the south side, giving a total round trip of some 7.1km (86

minutes on foot, 43 minutes on horseback and 22 minutes by cycle).

Based on the criteria in paragraph 13.7.15, the severance incurred during

the period of reconstruction would be adjudged as severe.



MARCH 2015

PAGE 13-30

13.7.22 Reconstruction of Ascot Road overbridge will have an impact on

movements between communities to the north and south of the M4 and

vice versa. It forms a link in conjunction with the A308(M) to connect

junction 8/9 of the M4 with Holyport and residential areas on to Bracknell.

However, the bridge is proposed to be constructed offline, allowing traffic

and pedestrians to continue to use the existing bridge whilst the new

bridge is constructed, such that no severance issues are anticipated.

13.7.23 Monkey Island Lane overbridge provides access from the village of Bray

to the north of the M4 to residential properties and facilities to the south of

the M4, including the Monkey Island Hotel. Monkey Island Lane is a no-

through-road with a section to the south of the M4 comprising a bridleway

and forms part of the route of NCN4. The new bridge will be built offline to

the western side of the existing bridge to enable the latter to remain in use

until the new bridge is completed. As such, no severance issues are

anticipated.

13.7.24 Alterations are proposed to the Huntercombe Spur overbridge at

junction 7 of the M4. The overbridge comprises two structures, one for

each direction of movement, and forms part of a trumpet-shaped junction

at the end of a 1km long dual two-lane road which links the M4 to the A4

Bath Road between Maidenhead and Slough. Reconstruction will be

offline, with traffic using one new span in two directions to allow sequential

demolition and reconstruction of the adjacent spans. Accordingly,

disruption to users will be minimal.

13.7.25 Wood Lane overbridge provides a link across the M4 for 16 properties on

Wood Lane, together with access to Thames Water’s Slough sewage

treatment plant. The route to the south of Wood Lane connects with a

walking/cycling path along the banks of the Jubilee River. The overbridge

is proposed to be reconstructed offline, to the east of the existing bridge, to

enable the latter to remain open during the construction period, such that

no severance issues are anticipated.

13.7.26 Datchet Road overbridge carries the B376 Datchet Road, an all-purpose

urban single carriageway, linking the towns of Slough to the north and

Datchet to the south. The structure is proposed to be rebuilt offline to the

east of its current location enabling it to remain open during the

construction period. Due to the overbridge being constructed offline, there

will be no community severance issues.



MARCH 2015

PAGE 13-31

13.7.27 Riding Court Road overbridge provides a link between the town of

Datchet and the area of Langley on the outskirts of Slough. It provides

access in particular for employees from the Datchet area and other

residential areas to the south of the M4 travelling to businesses in either

the Riding Court Farm development or the Computer Associates

Technologies business to the north of the M4. The structure is to be

reconstructed offline and therefore there will be no significant disruption to

these movements.

13.7.28 The Thames Bray underbridge will be widened. This may have

implications for walkers, cyclists and boat users along this stretch of the

River Thames during the widening works. There will be a need for a

number of short-term closures of the waterway to river traffic to allow

bridge beam lifts. There are also three footpaths/cycleways which provide

local links to the Thames Valley section of NCN4 to consider:

a) the footpath/cycleway over the river on the south side of the M4 is

not affected by the widening works and will be kept open with a

consequential neutral effect;

b) the footpath/cycleway over the river on the north side of the M4 will

be closed for the duration of the works. Signed diversions will be

provided via Monkey Island Lane to the west (a distance of 1.1km –

i.e. 13 minutes on foot, 7 minutes on horseback and 4 minutes by

cycle) and Marsh Lane to the east (a distance of 1.7km – i.e. 20

minutes on foot, 10 minutes on horseback and 5 minutes by cycle)

which, being over 500m in length, constitutes a severe effect under

DMRB criteria; and

c) the tow-path under the bridge on the east side of the river will be

isolated from the works and kept open during construction.

However, like the river navigation route, short-term closures will be

required during the bridge beam lift and, as such, there will be

minimal effects on users of both the river and this tow path. The

Windsor Branch Railway underbridge is proposed to be widened

asymmetrically to the south. The structure is located at the end of

the slip roads to junction 6 of the M4 and provides the M4 with a

route over the Slough to Windsor and Eton branch railway line.

Cycle and walking routes pass along either side of the railway line

in this location, under the M4. There is likely to be an adverse

impact on users of these routes at certain times as the underbridge

widening work takes place over the course of 27 months.



MARCH 2015

PAGE 13-32

Depending on which track is closed and the intended direction of

travel, the diversion routes vary between an additional 300m

(moderate impact - 4 minutes on foot, 2 minutes on horseback or 1

minutes by cycle) and an additional 1km (severe impact – 12

minutes on foot, 6 minutes on horseback or 3 minutes by cycle).

However, at most times, these routes will remain open to users, and

consequently the impact will be in place for a short duration.

13.7.29 In summary, a total of 11 overbridges and two underbridges, together with

a number of culverts and subways are proposed to be reconstructed as

part of the construction of the Scheme. Seven of the structures will be

constructed offline (or without significant disruption to users in the case of

the two underbridges). Four of the overbridges are proposed to be

constructed online and, accordingly, will have effects on local communities

that, in DMRB terms, are adjudged to be severe. However, these effects

are for a limited duration of between 9 and 12 months whilst the bridges

are under construction.

Operation

Vehicle travellers

View from the road

13.7.30 As the M4 already exists and the Scheme introduces minor highway

alignment modifications, together with additional driver information,

reallocation of carriageway space and minor carriageway widening, the

view from the M4 is not considered to change materially, nor will the views

of the M4 from other local roads change materially as set out in chapter 8

Landscape.

13.7.31 However, there will be changes to the frequency and number of signs and

gantries. 133 additional gantries and associated signs are proposed as

part of the Scheme, as described in detail in the EDR. The assessment of

the view from the road within DMRB was developed principally to assess

new roads. Four assessment criteria are set out in DMRB for the

assessment of travellers’ ability to see the surrounding landscape – no

view, restricted view, intermittent view and open view. Of these,

“intermittent view” (a road generally at ground level but with shallow

cuttings or barriers at intervals) is considered to best represent the M4.

The effect of the introduction of the additional infrastructure associated

with the Scheme will be to introduce further intermittent, short timescale,

interruptions to the view.



MARCH 2015

PAGE 13-33

13.7.32 As there are no specific assessment ‘significance criteria’ or ‘magnitude of

impact’ assessment frameworks associated with ‘view from the road’ set

out in DMRB, a qualitative assessment using professional judgment,

based on the above criteria, is considered appropriate. On this basis, it is

considered that the Scheme will have a minor adverse impact on the

basis that the additional gantries that are necessary for the information

system signs will provide intermittent interruptions to the view, albeit ones

that are consistent with typical motorway infrastructure. By reference to the

guidance within DMRB on determining significance of environmental

effects (Ref 13-4, Chapter 2) the effect is adjudged to have a slight level

of significance as it is considered to be a factor local to the M4.

Driver stress

13.7.33 Operational effects are presented in Tables 13.21, 13.22, 13.23 and 13.24

for eastbound and westbound drivers on the M4 for the Do Minimum and

Do Something 2037 scenarios.

Table 13.21 Predicted driver stress experienced by eastbound M4 drivers for the Do Minimum 2037

M4 junctions

Link

2037 Do Minimum




(km/hr)

Average HGVs

(%)

Driver stress level

12-11 Mainline 2293 80 6.5% High

11-10 Mainline 2288 80 6.2% High

10-8/9 Mainline 2157 83 5.5% High

8/9-7 Mainline 2184 83 5.4% High








MARCH 2015

PAGE 13-34

Table 13.22 Predicted driver stress experienced by westbound M4 drivers for the Do Minimum 2037

M4 junctions

Link

2037 Do Minimum




Average HGVs

(%)

Driver stress level

12-11 Mainline 2028 87 5.7% High

11-10 Mainline 2133 84 5.4% High

10-8/9 Mainline 2032 86 5.0% High

8/9-7 Mainline 2071 85 5.2% High






Table 13.23 Predicted driver stress experienced by eastbound M4 drivers for the Do Something 2037

M4 junctions

Link

2037 Do Something




(km/hr)

Average HGVs

(%)

Driver stress level

12-11 Mainline 1951 89 5.9% High

11-10 Mainline 2131 84 5.5% High

10-8/9 Mainline 1951 89 5.0% High

8/9-7 Mainline 2001 87 5.0% High




4b-4 Mainline 1522 89 4.2% Moderate




MARCH 2015

PAGE 13-35

Table 13.24 Predicted driver stress experienced by westbound M4 drivers for the Do Something 2037

M4 junctions

Link

2037 Do Something

Average peak hourly flow per lane

(flow units/hr)


Average HGVs

(%)

Driver stress level

12-11 Mainline 1676 95 5.6% High

11-10 Mainline 1829 92 5.1% High

10-8/9 Mainline 1772 93 4.9% High

8/9-7 Mainline 1854 90 4.9% High




4b-4 Mainline 1199 111 4.3% Low


13.7.34 The net effects of these changes are described below.

13.8 Net effects of the Scheme on vehicle travellers in the design year (2037)

13.8.1 As noted in paragraph 13.2.24, given the lack of ‘significance criteria’

contained within DMRB, and the relative, indicative nature of the

assessment methodology, an assessment of the net effect of the

introduction of the Scheme based on professional judgement, by

comparing the 2037 Do Minimum and Do Something scenarios, is

required. This is presented below.

13.8.2 Table 13.25 compares driver stress for the Do Something and Do

Minimum scenarios in the eastbound direction for the Design Year (2037).

Table 13.25 Comparison of driver stress for the Do Minimum and the Do Something for the Design Year (2037) for eastbound M4 drivers

M4 junctions

Link

Driver stress level

2037 Do Minimum

2037 Do Something

2037 Do Something vs

Do Minimum



10-8/9 Mainline High High 0




5-4b Mainline High High 0

4b-4 Mainline High Moderate +


Net Effect +1



MARCH 2015

PAGE 13-36

13.8.3 There is little change between the Do Minimum and Do Something

scenarios, except for a beneficial effect identified between junction 4 and

4b.

13.8.4 Table 13.26 compares driver stress for the Do Something and Do

Minimum scenarios in the westbound direction for the Design Year (2037).

Table 13.26 Comparison of driver stress for the Do Minimum and the Do Something for the Design Year (2037) for westbound M4 drivers

M4 section

Link

Driver stress level

2037 Do Minimum

2037 Do Something


Do Minimum



10-8/9 Mainline High High 0




5-4b Mainline High High 0

4b-4 Mainline High Low +


Net Effect +2

13.8.5 In the westbound direction, there is little change between the Do Minimum

and Do Something scenarios, again with beneficial effects identified

between junctions 4 and 4b (on the opposite carriageway) and between

junctions 3 and 4.

13.8.6 Tables 13.27, 13.28 and 13.29 compare driver stress for the Do

Something and Do Minimum scenarios for the local, connected or affected

road network for the Design Year (2037).

Table 13.27 Comparison of driver stress for the Do Minimum and the Do Something for the Design Year (2037) for the M4 approaches

M4 junction

Link

Driver Stress Level

2037 Do Minimum

2037 Do Something

2037 Do Something

vs Do Minimum

12

A4W towards Theale High High 0

A4E from Theale Low Low 0

A4W towards Calcot Moderate Moderate 0

A4E from Calcot Moderate Moderate 0

11

A33N from Three Mile Cross Moderate Moderate 0

A33S towards Three Mile Cross Moderate Moderate 0

A33N approach from Reading Moderate Moderate 0

A33S towards Reading Moderate Moderate 0

B3270W from Whitley Wood High High 0



MARCH 2015

PAGE 13-37

M4 junction

Link

Driver Stress Level

2037 Do Minimum

2037 Do Something

2037 Do Something

vs Do Minimum

B3270E towards Whitley Wood High High 0

10

A329MN towards Winnersh Moderate Moderate 0

A329MS from Winnersh Moderate Moderate 0

A33N from Bracknell High High 0

A33S towards Bracknell High High 0

8/9

A404N towards Bisham Moderate Moderate 0

A404S approach from Bisham High High 0

A308MN towards Maidenhead Low Low 0

A308MS from Maidenhead High High 0

7 M4 Spur towards Slough High High 0

M4 Spur from Slough Low Low 0

6

A355N towards Slough High High 0

A355S approach from Slough Low Moderate -

A355N from Windsor Low Low 0

A355S towards Windsor Low Low 0

5

A4W towards Slough Moderate Moderate 0

A4E from Slough Moderate Moderate 0

A4W from Heathrow High High 0

A4E towards Heathrow High High 0

B470W towards Datchet Moderate Moderate 0

4b

M25C north of junction High High 0

M25A north of junction High High 0

M25C south of junction High High 0

M25A south of junction High High 0

4

M4 Spur towards Heathrow Moderate Moderate 0

M4 Spur from Heathrow Moderate Moderate 0

A408N towards Uxbridge High High 0

A408S from Uxbridge High High 0

3

A312N towards Southall Moderate Moderate 0

A312S from Southall Moderate Moderate 0

A312N from Heathrow Moderate Moderate 0

A312S towards Heathrow Moderate Moderate 0

Net Effect -1

13.8.7 Again, there is little net change, with only one link, the A355S approach

from Slough connected to junction 6, where drivers would experience an

increase in driver stress.



MARCH 2015

PAGE 13-38

Table 13.28 Comparison of Driver Stress for the Do Minimum and the Do Something for the Design Year (2037) for the A4 Link

M4 junctions

A4 Link

Driver stress level

2037 Do Minimum

2037 Do Something


Do Minimum

11-12 A4W from Reading Moderate Moderate 0

A4E towards Reading High High 0

10-11 A4W towards Reading Moderate Moderate 0

A4E from Reading High High 0

8/9-10 A4W towards Reading High High 0

A4E from Reading High High 0

7-8/9 A4W towards Maidenhead High High 0

A4E from Maidenhead Moderate Moderate 0

6-7 A4W towards Maidenhead Moderate Moderate 0

A4E from Maidenhead Moderate Moderate 0

5-6 A4W towards Slough High High 0

A4E from Slough High High 0

4b-5 A4W from Heathrow High High 0

A4E towards Heathrow High High 0

3-4 A4W towards Heathrow High High 0

A4E from Heathrow High High 0

Net Effect 0

13.8.8 There is no assessed net change in driver stress levels between the Do

Minimum and Do Something scenarios for the A4 link roads. Accordingly,

the effect of the Scheme on driver stress for users of the A4 link roads is

neutral.

Table 13.29 Comparison of Driver Stress for the Do Minimum and the Do Something for the Design Year (2037) for M4 Crossing Roads

M4 junctions

M4 Crossing Link

Driver stress level

2037 Do Minimum

2037 Do Something

2037 Do Something

vs Do Minimum

10-11

A327N north of B3270 towards Reading High High 0

A327S north of B3270 from Reading High High 0

A327N south of B3270 from Shinfield High High 0

A327S south of B3270 towards Shinfield

High High 0

A329N crossing M4 towards Reading High High 0

A329S crossing M4 from Reading High High 0

A327N north of B3270 towards Reading High High 0

8/9/10 A321N crossing M4 from Wokingham Moderate Moderate 0

A321S crossing M4 towards Wokingham

Low Moderate -

7-8/9

A330N crossing M4 towards Maidenhead

High High 0

A330S crossing M4 from Maidenhead High High 0

A330N crossing M4 towards Maidenhead

Moderate Moderate 0



MARCH 2015

PAGE 13-39

M4 junctions

M4 Crossing Link

Driver stress level

2037 Do Minimum

2037 Do Something

2037 Do Something

vs Do Minimum

A330S crossing M4 from Maidenhead High High 0

5-6

A332N crossing M4 towards Slough High High 0

A332S crossing M4 from Slough High High 0

B376N crossing M4 towards Slough Low Low 0

B376S crossing M4 from Slough Low Low 0

4-4B A408W towards Heathrow High High 0

A408E from Heathrow High High 0

Net Effect -1

13.8.9 Again, there is little net change on driver stress for travellers crossing the

M4, with only one link, the A321S crossing the M4 towards Wokingham

connected to junction 6, where drivers would experience an increase in

driver stress. Overall this is assessed as a negligible effect and with no

change on the majority of roads, the overall significance is assessed as

neutral.

13.8.10 It should be noted that the assessment reported above uses the rigid

assessment framework put forward in DMRB for the topic of driver stress.

As such, the two improvements in driver stress and the deterioration in

driver stress on two off-site links is not considered to be a definitive

assessment and so it is appropriate to apply professional judgement in this

topic, as described above. This assessment is set out below.

Augmented assessment of driver stress/journey quality

13.8.11 As noted within paragraph 13.2.26, other factors not included within the

pure driver stress speed/flow assessment framework should be

considered.

13.8.12 Journey time reliability will improve as a result of the introduction of the

Scheme. Previously completed smart motorway schemes have

demonstrated improvements in journey time reliability. For example, as

part of a comprehensive study into the post-opening effects of the pilot

smart motorway scheme on the M42, a 22% reduction in journey time

variability was reported (Ref 13-12). As the Scheme will introduce similar

technology to that implemented as part of the M42 scheme, that scheme is

considered an appropriate comparator to the present Scheme and similar

beneficial improvements to journey time variability are expected as a result

of this Scheme to those experienced on the M42.



MARCH 2015

PAGE 13-40

13.8.13 Road layout and junction frequency are not considered to change

materially as a result of the introduction of the Scheme. As such, the Do

Minimum to Do Something effect of the Scheme is considered to be

neutral. In addition to the benefits associated with the introduction of a

smart motorway, following consultation it has been decided to resurface all

lanes with a Thin Surface Course System, otherwise known as “low noise”

surfacing, along the complete Scheme extent. With this mitigation in place,

in addition to the predicted negligible changes or decreases in noise levels

within the Scheme corridor with the Scheme in operation, the surfacing will

reduce tyre noise7 and consequently in-vehicle noise levels, which will be

beneficial to driver stress.

13.8.14 An important objective of the Scheme is to continue to deliver a high level

of safety performance of the network using smart motorway techniques.

By way of reference, a study of the safety benefits of the M42 pilot smart

motorway reported a 55.7% improvement in (personal injury) accidents as

a result of that scheme (Ref 13-13). Again, as a smart motorway scheme

which implemented similar technology to that proposed as part of this

Scheme, the M42 is considered to be an appropriate comparator for the

Scheme.

13.8.15 Driver information will improve considerably as a result of the introduction

of the Scheme - additional Variable Message Signs ("VMS") being a key

feature of smart motorways. The reduction of general congestion (Ref 13-

14) and the likelihood of ‘traffic flow breakdown’ are other key outcomes

that have been identified from studies following the introduction of a smart

motorway (Ref 13-15).

13.8.16 Each of these factors are considered by DMRB as being able to reduce

driver stress. Whilst these factors fall outside the speed flow assessment

framework contained in DMRB, based on professional judgment and taken

together, the factors referred to above are considered to provide a

beneficial impact on driver stress.

13.9 Cumulative effects

13.9.1 The Design Year (2037) traffic data used to calculate driver stress

included committed developments which could affect the Scheme, as

listed in Appendix 16.2. Therefore, cumulative effects have been taken into

account within this assessment.

7 Further details are provided in chapter 12 ‘Noise and Vibration’.



MARCH 2015

PAGE 13-41

13.10 Limitations encountered in compiling the ES

13.10.1 The duration of bridge closure and length of route diversions noted above

are subject to revision following the appointment of the contractor.

However, the assessment presented in this report has been based on the

principles for the approach to construction and sequence of activities that

are described in the EDR. Where assumptions have been made in respect

of the extent of diversion involved, distances and times have been based

on a journey from one side of each structure to a point on the immediate

opposite side of the structure to reflect the maximum potential diversion

and consequently a worst case approach has been adopted in the

assessment.

13.11 Summary

13.11.1 The residual effects that could arise from construction and operation of the

Scheme are set out in Table 13.30.

Table 13.30 All travellers impact summary

Impact

description Receptor(s)

affected

Significance of residual

effect

Temporary impacts

Temporary closure of

overbridges and underbridges

during construction

Speed and flow reductions

associated with 50 mph speed

limit

Local road users

Pedestrians

Cyclists

Equestrians

M4 road users

Slight Adverse

Beneficial8

8 By using speed flow tables within DMRB. This is counter intuitive with driver stress likely to increase

associated with a reduction in speed limit during construction.



MARCH 2015

PAGE 13-42

Impact

description Receptor(s)

affected

Significance of residual

effect

Permanent impacts

With the Scheme in place driver stress will be lower due to

improved driver information,

smoother traffic flow and reduced

congestion

M4 road users

Beneficial

Documents

13 EFFECTS ON ALL TRAVELLERS - Planning Inspectorate · ENVIRONMENTAL STATEMENT CHAPTER 13 EFFECTS ON ALL TRAVELLERS MARCH 2015 PAGE 13-3 refers to 'new roads', it is considered that