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2 SCHEME CONTEXT

2.1 Introduction

2.1.1 This chapter describes the principal characteristics of the areas surrounding the links of the M4 that are affected by, and comprised within, the Scheme. The existing engineering features along the Scheme are described in chapter 4 of this Environmental Statement (“ES”), along with the proposed works to each link. Features of particular relevance to the topics assessed in the Environmental Impact Assessment (“EIA”) process are also described in greater detail in the topic-specific chapters of this ES (chapters 6 to 15). 2.1.2 Along the Scheme, the main conurbations are Reading, Maidenhead, , Hillingdon and Hounslow. Smaller, but notable urban areas include , , Windsor, West Drayton and Hayes. Figure 1 (see chapter 1) provides an overview of the location of the Scheme. The Scheme location plan is presented in Drawing 2.1 Sheets 1 to 11 in Document Reference 6.2 (ES Figures). All other drawings referenced in this chapter are also presented in Document Reference 6.2 (ES Figures). Table 2.1 below provides a summary of locations accessed from the Scheme. Table 2.1 Locations accessed from the Scheme

Junction Locations accessed

12 A4, Reading (west), Theale

Services Reading Motorway Service Area ("MSA")

11 A33, Basingstoke, Reading (central and south)

10 A329(M), Reading (east), Wokingham, Bracknell

8/9 A404(M), , Henley, A308(M), Maidenhead

7 A4, Slough (west)

6 A355, Slough (central); A322, Windsor

5 A4, , Langley; B470, Eton, Datchet

4b M25, M40, M1, M11, M3, M23, M20, Heathrow Airport (Terminals 4, 5 & Cargo), Gatwick Airport, Watford, Oxford,

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Junction Locations accessed Stansted Airport, Maidstone

4 Heathrow Airport (Terminals 1, 2 & 3), A408, Uxbridge, Hillingdon

3 Heathrow Airport (Terminals 4, 5 & Cargo), A312, Hayes, Harrow, Hillingdon, Hounslow

2.2 Junction 12 to junction11

2.2.1 The M4 between junction 12 (Theale) and junction 11 () is approximately 7.3km long with three running lanes in each direction. There is also a hard shoulder on the nearside of each carriageway and lighting columns are located in the central reserve. 2.2.2 This section of the M4 skirts the south-west to southern edge of Reading, which forms the principal settlement in this location (refer to Drawing 2.1, Sheets 1 and 2). 2.2.3 To the western extremity of the Scheme, west of junction 12, lies the North Wessex Downs Area of Outstanding Natural Beauty (“AONB”) (refer to Drawing 8.2, Sheet 1), the Sulham and Tidmarsh Woods and Meadows Site of Special Scientific Interest ("SSSI"), and Pincent’s Kiln SSSI. To the east of junction 12, the M4 crosses the Kennet and Avon Canal and then skirts south of the Reading urban area, through an area of agricultural land within which extensive gravel extraction activity has occurred, resulting in water filled gravel pits. 2.2.4 Average daily traffic flows along the M4 taken from the Agency’s traffic counting system in 2013 indicate that this link of the route carries approximately 108,100 vehicles per day, of which 10% are heavy goods vehicles (“HGVs”). 2.2.5 This link of the M4 is located within the local authorities of West , Wokingham Borough and Reading Borough respectively (refer to Drawing 16.1). 2.2.6 Key features along this link of the M4 are (from west to east): a) junction 12, a gyratory, is elevated above the main M4 carriageway on two overbridges: Theale Interchange West and Theale Interchange East;

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b) immediately at the end of the eastbound slip road is the Theale Railway underbridge, which carries the M4 over the Western Region mainline railway; c) the M4 then follows a downward gradient over the next three structures, which are Holy Brook Underbridge, Underbridge and Wellmans Farm Access Underbridge; d) the Reading MSAs are located on both sides of the M4. The M4 through this area is on a slight downward gradient. Burgfield Road overbridge spans the eastbound merge and westbound diverge slip roads for the Reading MSA; e) further along the M4 is Mortimer Line Railway Underbridge and Poundgreen Road overbridge; f) before junction 11, noise barriers are located on the verge of the eastbound carriageway (575m in length), and on the on-slip to the westbound carriageway (320m in length); and g) junction 11, a gyratory, is elevated above the main carriageway of the M4 on four overbridges.

2.3 Junction 11 to junction 10

2.3.1 The M4 between junction 11 (Three Mile Cross) and junction 10 (Winnersh) is approximately 8.7km long with three running lanes in each direction. There is also a hard shoulder on the nearside of each carriageway and lighting columns are located in the central reserve. 2.3.2 From junction 11, the M4 continues around the southern suburbs of Whitley and Lower to Winnersh at junction 10. To the south of the M4, the area is characterised by smaller villages and settlements, including and , until reaching the outskirts of Wokingham to the south of junction 10 (refer to Drawing 2.1, Sheets 2 to 4). 2.3.3 Between junction 11 and junction 10, the M4 passes through an area of agricultural land predominantly within the low lying floodplain of the , and to the east passes between the urban edges of Sindlesham, Winnersh and Wokingham. Agricultural land is interspersed with a number of woodlands and copses, with trees along the River Loddon corridor. The urban areas nearest to the M4 predominantly comprise modern residential suburbs of Reading north of the M4.

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2.3.4 Average daily traffic flows along the M4 taken from the Agency’s traffic counting system in 2013 indicate that this section of the route carries approximately 109,800 vehicles per day, of which 10% are HGVs. 2.3.5 This section of the M4 is located within Reading Borough and Wokingham Borough respectively (refer to Drawing 16.1). 2.3.6 Key features along this link of the M4 are (from west to east): a) junction 11, a gyratory, is elevated above the main M4 carriageway on four overbridges; b) east of the junction 11 slip roads, the M4 continues past Shinfield Footbridge, gradually rising up to Shinfield Road overbridge, which carries the A327 over the M4. Proposals are being promoted by a third party to construct a new overbridge adjacent to this structure to carry the proposed Reading Eastern Relief Road (see Appendix 16.1); c) a noise barrier (475m long, 1.8m high) is located on the eastbound carriageway verge around Shinfield Footbridge; d) further east is Cutbush Lane overbridge, followed by the River Loddon Underbridge, Mill Lane Underbridge, and King Street Lane Underbridge; e) after Mill Lane Underbridge, noise barriers are located on both verges. The noise barrier on the westbound verge is 455m in length, and ends a few hundred metres after King Street Lane Underbridge. The noise barriers in the eastbound verge are split into a number of sections totalling 1.2km in length, and continuing up to just before the start of the junction 10 slip roads; f) after King Street Lane Underbridge, the M4 follows a slight downward gradient to the next structure, Reading Road Underbridge; g) the downward gradient steepens slightly before the M4 reaches the Southern Region Winnersh Underbridge, which supports the M4 over the Southern Region Railway Line; and h) the M4 then continues on a downward gradient to the slip roads for junction 10, which is an interchange between the M4 and the A329(M).

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2.4 Junction 10 to junction 8/9

2.4.1 The M4 between junction 10 (Winnersh) and junction 8/9 (Holyport) is approximately 11km long, and has three running lanes in each direction. There is also a hard shoulder on the nearside of each carriageway, but there is no lighting between these junctions. 2.4.2 This link of the M4 passes through a relatively sparsely populated rural area, characterised by scattered farms, homesteads and rural businesses. This rural area lies between Reading and Wokingham to the west, and Maidenhead to the east (refer to Drawing 2.1, Sheets 4 to 6). 2.4.3 The M4 is located within Green Belt land (shown on Drawing 8.2) from The Straight Mile overbridge (east of junction 10) to junction 8/9. Gently undulating agricultural land is interspersed with considerable woodland cover, and mature hedgerows define field boundaries. Settlement is limited, with Shurlock Row, White Waltham, Paley Street and Stud Green forming the principal villages prior to reaching Maidenhead. The M4 verges provide established tree planting which integrates well with the local wooded landscape. 2.4.4 Average daily traffic flows along the M4 taken from the Agency’s traffic counting system in 2013 indicate that this section of the route carries approximately 116,600 vehicles per day, of which 8% are HGVs. 2.4.5 This section of the M4 is located within Wokingham Borough, Bracknell Forest Borough and the Royal Borough of Windsor and Maidenhead respectively (refer to Drawing 16.1). 2.4.6 Key features along this link of the M4 are (from west to east): a) junction 10 is an interchange between the M4 and the A329(M), with the A329(M) crossing the M4 on an overbridge; b) from junction 10, the M4 rises gradually to Bill Hill overbridge, which carries the A321 over the M4, and then continues to rise before taking a downward gradient to The Straight Mile overbridge; c) the M4 then follows a slight rise, followed by a slight downward gradient to Billingbear Farm overbridge, Hammonds Wood overbridge (which carries the B3018 over the M4), and Beenhams Heath overbridge; d) the M4 then gradually rises to Littlefield Green overbridge, which carries the B3024 over the M4;

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e) Paley Street Farm overbridge is situated on a slight downward slope, followed by Stud Green Access overbridge, which carries Thrift Lane over the M4; and f) the M4 then continues on this slight downward gradient to junction 8/9, which is a gyratory, elevated above the main carriageway of the M4 on two overbridges. This gyratory serves the A404(M) and A308(M), both to the north of the junction.

2.5 Junction 8/9 to junction 7

2.5.1 The M4 between junction 8/9 (Holyport) and junction 7 (Huntercombe) is approximately 5km long, and has three running lanes in each direction. There is also a hard shoulder on the nearside of each carriageway, but each hard shoulder has intermittent breaks, or discontinuities. The main carriageway lighting columns are located in the central reserve. 2.5.2 This link of the M4 is located within Green Belt land (shown on Drawing 8.2) and passes north of Holyport and the urban fringe area to the south of Maidenhead, before returning to the Green Belt. From here the M4 passes the village of Bray to the north before crossing the and then continuing east past the villages of Dorney Reach and Dorney to the south (refer to Drawing 2.1, Sheets 6 and 7). 2.5.3 The River Thames and the nearby man-made (which functions as a flood alleviation channel) and recreational lakes, together with adjacent wet pasture, occupy most of the land between settlements. These watercourses and areas of open water are lined by riparian tree species, giving considerable vegetation cover in the local landscape. 2.5.4 Average daily traffic flows along the M4 taken from the Agency’s traffic counting system in 2013 indicate that this section of the route carries approximately 125,200 vehicles per day, of which 9% are HGVs. 2.5.5 This section of the M4 is located within the Royal Borough of Windsor and Maidenhead and South District (refer to Drawing 16.1). 2.5.6 Key features along this link of the M4 are (from west to east): a) junction 8/9 is formed as a gyratory, elevated above the main carriageway of the M4;

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b) Ascot Road overbridge (which carries the A330 over the M4) is located on a slight upward gradient. To the east, the M4 passes over the A308, Windsor Road underbridge. Noise barriers are located on either side of the Windsor Road overbridge. These total 450m in length on the eastbound carriageway verge, and 800m in length in the westbound carriageway verge; c) the M4 then continues on an elevated section to The Cut culvert. There is a Police Observation Platform (“POP”) on the westbound carriageway between the two underbridges; d) the M4 continues to rise up before dipping down towards Monkey Island Lane overbridge, which carries a local unclassified road, connecting the village of Bray with a number of dwellings and several hotels and other businesses. The carriageways narrow at this point and the hard shoulder is discontinuous as the M4 passes under the bridge; e) the M4 then crosses over the River Thames on the Thames Bray Underbridge which also carries footway/cycleways over the river, one on each side of the M4. The M4 hard shoulders are discontinuous over this bridge; f) the M4 level then falls to the next major structure which is Marsh Lane overbridge, with a short discontinuity in the M4 hard shoulder. Marsh Lane is an unclassified road linking Dorney and Dorney Reach to the south, with the A4 Bath Road to the north. In this area, a 585m length of noise barrier is located on the eastbound carriageway verge, and 340m in the westbound carriageway verge; g) the M4 then crosses over the Thames (Maidenhead) Flood Channel (Jubilee River); h) continuing eastwards from the Jubilee River, the M4 reaches Lake End Road overbridge (B3026), with a short discontinuity in the hard shoulder. Just after the overbridge a 160m long noise barrier is locate in the westbound carriageway verge; and i) junction 7, at Huntercombe, is a trumpet shaped junction at the end of the Huntercombe Spur link road, which links the M4 to the A4 Bath Road between Maidenhead and Slough (see Drawing 2.1, Sheet 10). The link road crosses over the M4 on the Huntercombe Spur overbridge and then swings around to form the “loop” of the trumpet shape.

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2.6 Junction 7 to junction 6

2.6.1 The M4 between junction 7 (Huntercombe) and junction 6 (Chalvey) is approximately 3km long, and has three running lanes in each direction. There is also a hard shoulder on the nearside of each carriageway, but each hard shoulder has discontinuities, as described below. The main carriageway lighting columns are located in the central reserve. 2.6.2 This link of the M4 is located within the northern fringe of the Green Belt (shown on Drawing 8.2) and between the outskirts of Slough to the north (including the area of Cippenham) and Eton Wick and the River Thames floodplain to the south (refer to Drawing 2.1, Sheets 7 and 8). 2.6.3 Slough sewage treatment works occupies land to the south-east of junction 7, between the M4 and the Jubilee River. 2.6.4 As it approaches junction 6, the M4 lies immediately north of, and runs parallel to, the Jubilee River. The River Thames is located further south beyond the villages of Dorney and Eton Wick. 2.6.5 To the south of junction 6 are the towns of Windsor and Eton where the world-renowned Windsor Castle and Eton College are located. The town of Windsor is located on an escarpment to the south of the River Thames and south-east of junction 6. 2.6.6 Average daily traffic flows along the M4 taken from the Agency’s traffic counting system in 2013 indicate that this section of the route carries approximately 125,600 vehicles per day, of which 8% are HGVs. 2.6.7 This section of the M4 is located within Slough Borough and South Buckinghamshire District (refer to Drawing 16.1). 2.6.8 Key features along this link of the M4 are (from west to east): a) junction 7, at Huntercombe, is a trumpet shaped junction. Both hard shoulders are currently discontinuous under the structure. Just after the junction, a 300m long noise barrier is located in the eastbound on-slip verge; b) further along the M4, situated on a very slight downward gradient, is Oldway Lane Accommodation overbridge, which carries an access track over the M4. The track is a bridleway used by equestrians connecting to a bridleway track parallel to the westbound carriageway. The M4 hard shoulder is discontinuous under the structure;

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c) there is an environmental bund to the eastbound verge located between Oldway Lane Accommodation overbridge and the next structure, Wood Lane overbridge, providing noise attenuation and screening to Cippenham. The bund is 1070m long; d) Wood Lane overbridge is situated on a very slight downward gradient. The structure carries Wood Lane, an unclassified local road over the M4, and provides the sole access for a number of residential properties and a sewage treatment works. There are discontinuities in the M4 hard shoulder in this location; e) there is also an environmental bund located adjacent to the parkland to the north of the M4 between Wood Lane overbridge and junction 6, approximately 650m long. (refer to Drawing 2.1 Sheet 11); f) further along the M4 to the east and situated on a very slight downward gradient, is Chalvey Culvert. This culvert carries a drainage channel through the embankment below the M4 and the junction 6 slip roads; and g) at junction 6 there is a 165m long noise barrier to the full length of verge to the eastbound diverge. Junction 6 itself is a gyratory, situated beneath the M4. The main carriageway of the M4 is carried over the junction by two underbridges.

2.7 Junction 6 to junction 5

2.7.1 The M4 between junction 6 (Chalvey) and junction 5 (Langley) is approximately 6km long, and has three running lanes in each direction. There is also a hard shoulder on the nearside of each carriageway, but each hard shoulder has discontinuities, as described below. The main carriageway lighting columns are located in the central reserve. 2.7.2 Land around this link of the M4 includes Green Belt land (shown on Drawing 8.2), and the Slough suburbs (including the areas of Upton Court Park, Ditton Park and Langley). This link of the M4 also passes to the north of the confluence of the Jubilee River with the River Thames, the town of Datchet and the (refer to Drawing 2.1, Sheets 8 and 9). 2.7.3 Average daily traffic flows along the M4 taken from the Agency’s traffic counting system in 2013 indicate that this section of the route carries approximately 136,300 vehicles per day, of which 8% are HGVs.

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2.7.4 This section of the M4 is located within Slough Borough and the Royal Borough of Windsor and Maidenhead (refer to Drawing 16.1). 2.7.5 Key features along this link of the M4 are (from west to east): a) junction 6 is formed of a gyratory, situated beneath the M4. The main carriageway of the M4 is carried over the junction by two underbridges: Chalvey Interchange West overbridge and Chalvey Interchange East overbridge. There is a 460m noise barrier to the eastbound verge within the junction; b) Windsor Branch Railway underbridge is located at the end of the slip roads to junction 6. A pedestrian guardrail is mounted on the south side of the underbridge, approximately 60m in length. There are no hard shoulders to the M4 on this bridge; c) further along the M4, situated on a slight downward gradient is the Slough Road (Prince of Wales) underbridge, which carries the M4 over the A332; d) from junction 6, and continuing to just after the Slough Road (Prince of Wales) underbridge, a series of noise barriers are located in the eastbound carriageway verge, totalling 1.1km in length. e) the downward gradient continues over the Water and Gas Main subway which provides a passage for utilities to cross beneath the M4. The carriageway over this structure has a discontinuous hard shoulder; f) Datchet Road overbridge is the next bridge to the east. This structure carries the B376 (Datchet Road). There are discontinuities in the M4 hard shoulder under this structure; g) the M4 continues on a slight downward slope to the Recreation Ground overbridge, which connects Upton Court Road and the track to Upton Court Park with the main road between Datchet and Slough. The carriageway over the structure is gated and believed to be used occasionally by the park staff, as well as being a public right of way used for access to the motocross club to the north- west of the structure. There are discontinuities in the M4 hard shoulder at this structure; h) west of the Recreation Ground overbridge, the Water Main Subway is located on a section of level carriageway;

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i) the M4 remains level on the approach to Riding Court Road overbridge, and a 785m long noise barrier is located in the westbound carriageway verge. The Riding Court Road provides access for the sand and gravel works around Riding Court Farm. There are discontinuities in the M4 hard shoulder at this structure; j) after Riding Court Road bridge, a 940m long noise barrier is located in the westbound carriageway verge, ending just after Ashley’s Arch Culvert. Ashley’s Arch Culvert comprises two structures: a 1.5m diameter concrete pipe and a 6.1m reinforced concrete box culvert. There is a discontinuous hard shoulder to the eastbound carriageway over the pipe culvert; and k) the M4 then continues under Hams Farm footbridge on an upward gradient through to junction 5, which is a gyratory, situated beneath the M4. The main carriageway of the M4 is carried over the junction by two underbridges and a subway.

2.8 Junction 5 to junction 4b

2.8.1 The M4 between junction 5 (Langley) and junction 4b (M25) is approximately 3km long, and has four running lanes in each direction. There is also a hard shoulder on the nearside of each carriageway, but each hard shoulder has discontinuities, as described below. The main carriageway lighting columns are located in the central reserve. 2.8.2 After passing under Sutton Lane overbridge, the M4 in this link is located within Green Belt land (shown on Drawing 8.2). From junction 5 the M4 passes from the eastern edge of Slough, through semi-rural surroundings to the M25 intersection at junction 4b. Where the urban area of Slough lies immediately adjacent to the M4, it predominantly comprises modern residential estates (refer to Drawing 2.1, Sheets 9 and 10). 2.8.3 East of Slough, the area to the north of the M4 is characterised by Richlings Park, Richlings Park golf course and farmland (traversed by high voltage power lines); a gravel pit, gravel pit lakes, sewage treatment works, an industrial estate, and farmland (traversed by high voltage power lines) lie to the south of the M4. 2.8.4 Average daily traffic flows along the M4 taken from the Agency’s traffic counting system in 2013 indicate that this section of the route carries approximately 145,700 vehicles per day, of which 9% are HGVs.

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2.8.5 This section of the M4 lies on the boundary of Slough Borough to the west, the London Borough of Hillingdon to the east, and South Buckinghamshire to the north-west (refer to Drawing 16.1). 2.8.6 Key features along this link of the M4 are (from west to east): a) junction 5 is formed of a gyratory, situated beneath the M4. The main carriageway of the M4 is carried over the junction by two underbridges and a subway. The subway provides a route for pedestrians to pass under the M4. There are elevated walkways leading away from the subway in both directions to spiral ramps down to pavement level at both sides of the gyratory. There is no hard shoulder over the structures; b) the M4 follows a slight downward gradient away from junction 5, with a series of noise barriers, totalling 1.2km in length, located in the eastbound carriageway verge, and a total of 515m in the westbound carriageway verge. Sutton Lane overbridge is located immediately at the end of the junction 5 slip roads and carries Sutton Lane over the M4; c) the M4 levels out as it approaches Old Slade Lane overbridge at the start of the junction 4b slip road. Before Old Slade Lane overbridge, a 340m noise barrier is located in the eastbound carriageway verge, and 520m in the westbound carriageway verge. 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. There are discontinuities in the M4 hard shoulder at this structure; and d) the main carriageway of the M4 continues on a slight upward gradient through to junction 4b, which is an interchange between the M4 and the M25.

2.9 Junction 4b to junction 4

2.9.1 The M4 between junction 4b (M25) and junction 4 (Heathrow) is approximately 3km long, and has four running lanes in each direction. There is also a hard shoulder on the near-side of each carriageway and lighting columns are located in both the central reserve and the verge.

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2.9.2 In this link, the M4 crosses the Wraysbury River and the River Colne before passing Saxon Lake to the south. The M4 is located within Green Belt land (shown on Drawing 8.2) west of Saxon Lake and forms the northern boundary of the Green Belt between Saxon Lake and junction 4 (refer to Drawing 2.1, Sheet 10). 2.9.3 The M4 then passes into the London Borough of Hillingdon between the urban area of West Drayton to the north, which predominantly comprises modern residential and commercial estates, and the villages of Harmondsworth and Sipson, and Heathrow to the south. 2.9.4 Harmondsworth and Sipson are situated between the Green Belt to the south of the M4, featuring active and reclaimed gravel pits, farmland and Heathrow Airport, the internationally important transport hub. The presence of the airport to the south of these settlements, together with its extensive ancillary developments, represents a major land-use within the area. 2.9.5 Average daily traffic flows along the M4 taken from the Agency’s traffic counting system in 2013 indicate that this section of the route carries approximately 160,300 vehicles per day, of which 6% are HGVs. 2.9.6 This section of the M4 is located within the London Borough of Hillingdon (refer to Drawing 16.1). 2.9.7 Key features along this link of the M4 are (from west to east): a) junction 4b is an interchange between the M4 and the M25, with the M25 crossing the M4 on a multi-span viaduct. Two of the junction 4b link roads pass over the M4 on viaducts, whilst the M4 passes over the other two link roads and Staines Branch Railway Line via the use of three underbridges: Staines Branch Line West underbridge, Staines Branch Line underbridge and Staines Branch Line East underbridge; b) Wraysbury River underbridge and River Colne underbridge are located within junction 4b and carry the M4 over the Wraysbury River and the River Colne respectively; c) towards the end of the junction 4b slip roads, the main carriageway separates forming a wide central reserve that is covered by dense vegetation. A noise barrier is situated on the eastbound verge, continuing up to junction 4, and totalling 1.9km in length;

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d) the M4 then passes under Little Benty North and South Footbridges, before arriving at Harmondsworth Road North and South overbridges; e) further along the M4, situated on a slight incline, is Sipson Road Subway, which provides pedestrian access under the M4 junction 4 slip roads; f) Holloway Lane underbridge is located further along the M4. The structure carries the M4 main carriageway and junction 4 slip roads over the A408; and g) at junction 4 there is an environmental barrier to the verge of the eastbound diverge. Junction 4 itself is a gyratory, situated beneath the M4. The main carriageway of the M4 is carried over the junction by two underbridges.

2.10 Junction 4 to junction 3

2.10.1 The M4 between junction 4 (Heathrow) and junction 3 (Hayes) is approximately 3km long with three running lanes in each direction. There is also a hard shoulder on the near-side of each carriageway and lighting columns are located in the central reserve. 2.10.2 This link is located within Green Belt land (shown on Drawing 8.2) and crosses over Frog’s Ditch and the River Crane. The M4 in this section is bounded to the north by the modern residential areas of Hayes and to the south by the village of Harlington and more open areas including Little Harlington Playing Fields and Cranford Park. Further south from the M4 corridor lies the eastern section of Heathrow Airport (refer to Drawing 2.1, Sheet 11). 2.10.3 Areas to the south of the M4 include open areas and wooded parkland, including Cranford Park Conservation Area and associated listed buildings (see Drawing 8.1). 2.10.4 Average daily traffic flows along the M4 taken from the Agency’s traffic counting system in 2013 indicate that this section of the route carries approximately 146,000 vehicles per day, of which 6% are HGVs. 2.10.5 Between junction 4b and junction 3 the M4 is located within the London Borough of Hillingdon and on the approach to and at junction 3 the M4 is located within the London Borough of Hounslow (refer to Drawing 16.1).

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2.10.6 Key features along this link of the M4 are (from west to east): a) junction 4 is formed of a gyratory, situated beneath the M4. The main carriageway of the M4 is carried over the junction by two overbridges: Airport Interchange West overbridge and Airport Interchange East overbridge; b) a series of noise barriers totalling 1.9km are located in the eastbound carriageway verge between junctions 4 and 3; c) the M4 follows a downward gradient away from junction 4. After approximately 1.4km the gradient almost levels out as it traverses over St. Peter’s Subway; d) Harlington High Street overbridge is located approximately 0.3km along the M4 at a similar gradient to the previous structure. This structure carries the A437 over the M4; e) further along the M4, Fuller subway is situated on a similar gradient to the previous two structures. From just west of Fuller Subway through to the next structure, a series of noise barriers totalling 565m in length are located in the westbound carriageway verge; f) St. Dunstan’s subway is located approximately 0.5km from the previous subway on a slightly upward gradient; and g) junction 3 is a gyratory, situated beneath the M4. The main carriageway of the M4 is carried over the junction by Cranford Parkway Viaduct.

2.11 Forecast traffic flows

2.11.1 As mentioned in chapter 1, despite a reduction in traffic volumes during the global financial crisis in 2008, long-term traffic trends show significant growth, which is predicted to result in more severe congestion without road improvements. 2.11.2 The ratio of actual traffic flow to its capacity (the total flow that a link is capable of handling) is a general way of indicating congestion. Where the ratio exceeds 85%, the links are becoming congested.

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2.11.3 Table 2.2 shows current (2013) and forecast ratios for each link along the Scheme. Traffic flow forecasts are taken from the traffic model developed to assess the Scheme. Forecast ratios are shown for the morning and evening peak periods for three years – the current baseline (2013), the proposed Opening Year (2022) and the Design Year taken to be 15 years later (2037). In each case, without the Scheme, the number of links shaded red (indicative of these links becoming congested) increases over time. Similarly, the number of links shaded black (where flow has reached capacity) is also forecast to increase. The links shaded yellow indicate links where traffic flows are approaching congestion. Those links shaded green do not have capacity issues. 2.11.4 Table 2.2 demonstrates that at peak times, traffic flows on many links are close to, or exceed, the total flow that the link is designed to handle and traffic on the M4 therefore suffers from heavy congestion, which leads to unpredictable journey times. As described in chapter 1, the Scheme will help to relieve this congestion by permanently converting the hard shoulder of the M4 to a running lane and using technology to vary speed limits and manage traffic.

ENVIRONMENTAL STATEMENT CHAPTER 2 SCHEME CONTEXT

MARCH 2015

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HIGHWAYS AGENCY – M4 JUNCTIONS 3 TO 12 SMART MOTORWAY

Table 2.2 Forecast ratios of traffic flow to capacity (without the scheme)

M4 - MM ALR Morning peak hour (07:00 - 08:00) Evening peak hour (17:00 - 18:00)

No Scheme Eastbound Westbound Eastbound Westbound

Description 2013* 2022 2037 2013* 2022 2037 2013* 2022 2037 2013* 2022 2037

M4 J12 to J11 73.5 99.4 100.0 60.5 82.1 88.9 74.5 94.5 100.0 78.1 88.2 90.8

M4 J11 to J10 69.9 100.0 100.0 66.2 85.7 92.1 77.4 96.1 100.0 78.7 92.8 96.1

M4 J10 to J8/9 73.9 96.7 100.0 76.3 82.7 87.2 77.4 85.1 90.1 80.6 94.7 97.9

M4 J8/9 to J7 85.3 97.0 100.0 75.6 80.1 84.9 79.2 83.8 87.7 80.6 100.0 100.0

M4 J7 to J6 81.6 91.6 93.5 74.0 82.9 88.6 75.9 83.0 85.5 79.2 94.5 98.6

M4 J6 to J5 80.8 96.9 99.6 84.7 87.9 93.0 81.4 91.4 95.0 84.4 97.3 100.0

M4 J5 to J4B 65.8 74.0 76.2 65.3 73.1 75.2 67.1 75.1 78.2 63.2 80.0 82.3

M4 J4B to J4 70.5 77.2 78.5 68.4 73.7 74.9 65.2 77.9 79.6 71.3 77.0 77.7

M4 J4 to J3 72.1 84.2 88.5 81.9 86.8 88.0 80.6 91.6 91.4 76.1 83.7 83.9

*2013 values are calculated using TRADS Weekday (Mon – Fri) data.

Key: Ratio of 100% >85% 75-80% <75% flow to capacity Reached capacity Becoming congested Approaching congestion No capacity issues

ENVIRONMENTAL STATEMENT CHAPTER 2 SCHEME CONTEXT

MARCH 2015

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