M4

Location Map ( geo)

View gallery (500)

From:

Chiswick, Middlesex (TQ19578)

To:

Pont Abraham, Carmarthenshire (SN575071)

Via:

Slough, Reading, Swindon, Bath, Bristol, Newport, Cardiff, Port Talbot, Swansea

Distance:

191.9 miles (308.8 km)

Meets:

M5, M25, M32, M48, M49, A33, A34, A4, A46, A48(M), A48, A308(M), A312, A329(M), A346, A350, A404(M), A419, A429, A449, A465, A470, A483, A4042, A4138, A4232

Former Number(s):

A4, A4(M), A48(M) (Port Talbot and Morriston bypasses)

Old route now:

M48, A404(M), A48(M) (Cardiff spur)

Primary Destinations

Heathrow Airport

Highway Authorities

Highways England • Welsh Government

HE Area 2 • HE Area 3 • HE Area 5 • South Wales TRA

Traditional Counties

Berkshire • Buckinghamshire • Carmarthenshire • Glamorgan • Gloucestershire • Middlesex • Monmouthshire • Wiltshire

Route outline (key)

M4	Chiswick — Pont Abraham
M4	Newport Southern Bypass
M4	Maidenhead bypass
M4	Severn Bridge and approaches

Junction List

Former junctions are shown on a thick grey background.

Junc	Westbound	Eastbound
1	Start of Motorway	A4 (E)
Bridge	Chiswick Flyover
2	A4	A4
	Heston services
3	A312	A312
4	(Airport Spur)	(Airport Spur)
4b	M25	M25
5	A4, B470	A4, B470
	Datchet services
6	A335	A335
7	A4	A4
Bridge	New Thames Bridge
8	A308	A308
8/9	A308(M), A404(M)	A308(M), A404(M)
	Maidenhead services
9a	C8750, C8711	C8750, C8711
9b	Temporary start of road	A4
	Warren Copse services
10	A329(M)	A329(M)
Bridge	Carters Hill Bridge
11	A33	A33
	Reading services
Bridge	Calcot Viaduct
12	A4	A4
	Ashes Copse services
13	A34	A34
14	A338	A338
	Membury services
15	A346, A419	A346, A419
16	A3102, B4005	A3102, B4005
	Ballard's Ash services
17	A350, A429, B4122	A350, A429, B4122
	Leigh Delamere services
18	A46	A46
	Pucklechurch services
19	M32	M32
20	M5	M5
21	M48	No Exit
21	A403	A403
	Aust services
22	M49	M49
22	A466	A466
Bridge	Prince of Wales Bridge
23	No Exit	M48
23a	A4810	A4810
	Wilcrick services
24	A48, A449, B4237	A48, A449, B4237
25	A4042, B4596	No Exit
25a	A4042	No Exit
Tunnel	Brynglas Tunnels
26	A4051	A4051
27	B4591	B4591
28	A48, A467	A48, A467
29	A48(M)	No Exit
30	A4232	A4232
31	A469	A469
32	A470, A4054	A470, A4054
33	A4232	A4232
34	A4119	A4119
35	A473	A473
36	A4061, A4063	A4061, A4063
37	A4229	A4229
38	A48	A48
	Port Talbot services
39	No Exit	No Exit
40	A4107	A4107
41	A48, A4241, B4286	A48, A4241, B4286
42	A483	A483, A48
43	A465, B4290	A465, B4290
44	A48, A4230, B4291, B4625	A48, A4230, B4290, B4625
45	A4067, B4603	A4067, B4603
46	A48, B4489	A48, B4489
47	A48, A483	A48, A483
48	A4138	A4138
49	A48, A483	Start of Motorway

The M4 is the London to South Wales Motorway. Running for about 190 miles from Chiswick in the west of the capital to a point some 12 miles southeast of Carmarthen in west Wales, it passes such important centres of population and industry as Reading, Swindon, Bristol, Cardiff, and Swansea. The route forms the bulk of the E30's Fishguard to Felixstowe route in the UK.

For detailed information about this topic, see Roads.org.uk Motorway Database: M4

Route

London – Reading

The road into London is one of few examples of truly urban major motorways which were built as intended. It was also a pioneer of modern features, boasting three CCTV cameras, detectors to report congestion and a never-used underfloor heating system which claimed there would never be a frost on the road. The elevated section claims to have been built without "any disruption" to the Great West Road beneath it.

The tensioned wire central reservation barrier fitted to the road at Langley was the first in the UK, and was used by TRL to test its effectiveness before the road opened.

Reading – Bath

Heading west towards Swindon

After Reading, the M4 becomes more rural and picturesque - travelling first through the North Wessex Downs, and then the southern Cotswolds. The motorway runs a few miles north of the A4 and the towns along it that, save for Swindon, are the main places that it serves. At junction 13 the motorway meets the major A34 north-south route, serving Newbury. At junction 14, Hungerford is served via the A338. Swindon has two junctions: junction 15, which serves also serves Marlborough via an extended A346, as well as the A417/A419 trunk dual carriageway to the M5 at Gloucester and junction 16, which serves western suburbs. Junction 17 serves Chippenham, with the A429 south of the junction having been renumbered A350 upon the opening of the motorway. Junction 18 with the A46 serves Bath.

Bath – Cardiff

Approaching the Second Severn Crossing from Newport

Cardiff – Pont Abraham

Elevated over Port Talbot

History

Perhaps surprisingly, the M4 may be counted Great Britain's second oldest motorway, as the Chiswick Flyover (then numbered A4, but now the first section of the M4) opened in 1959, a couple of months before the M1, M10, and M45. Other parts of this motorway started life as the A4(M) and A48(M), whilst the Severn and Wye Bridges – originally on the M4 but bypassed since 1996 by the Second Severn Crossing – now lie on the M48.

Opening dates

For detailed information about this topic, see CBRD Motorway Database: M4 Timeline

Future

Main Article: M4/Newport Southern Bypass

Improvements

2005 – M4 Jct 18 widening

The eastbound carriageway was widened from D3M to D4M on the approach to Junction 18 at Tormarton. The fourth lane was added to act as a crawler lane for slow vehicles travelling up the steep hill.

2010 – M4 Jct 29 to 32 widening

The motorway was widened from D2M to D3M between Junction 29 at Castleton to Junction 32 at Coryton. The scheme started in 2007 and was completed in 2010, costing around £99.2 million in total.

2011 – M4 Jct 24 to 28 variable speed limit scheme

The motorway between Junction 24 at Coldra and Junction 28 at Tredegar Park received variable speed limits in order to help relieve congestion in and around Newport. This section of the motorway saw the installation of new gantries and speed cameras, along with the replacement of the street lighting in the central reservation.

2014 – M4 Jct 19 to 20 smart motorway scheme

The motorway was upgraded to become a smart motorway between Junction 19 at Hambrook and Junction 20 at Almondsbury. The scheme started in 2012 and was completed in 2014. Features of this smart motorway include a dynamic hard shoulder and variable speed limits.

Junctions

Brentford Interchange

Main Article: Brentford Interchange

The Brentford Interchange (junction 2) is a compact 'ironing-board' interchange.

Colnbrook Interchange

Main Article: Colnbrook Interchange

The Colnbrook Interchange (junction 4b of the M4; junction 15 of the M25) is a large four-level stack interchange between the M4 and M25 motorways. It is unusual in that, in addition to the various different roads that make up the junction, there is also a railway line running through it.

Chieveley Interchange

Main Article: Chieveley Interchange

The Chieveley Interchange (junction 13) was upgraded in the late 2000s to a 3-level roundabout.

Almondsbury Interchange

Main Article: Almondsbury Interchange

The Almondsbury Interchange (junction 20 of the M4; junction 15 of the M5) is an important junction allowing direct interchange between the M4 and M5, and is additionally linked to junction 16 of the M5, which provides access to and from the A38. This junction was the first example of a four-level stack in the country. The link roads leading from the M4 to the M5 pass over the top level of the interchange whilst those from the M5 to the M4 pass underneath all other levels.

Coryton Interchange

Main Article: Coryton Interchange

The Coryton Interchange (junction 32) is a very large 3-level roundabout, with the A470. The circulatory carriageway of the roundabout is one of the longest in the country, clocking in at over a mile. The A470 mainline goes over the roundabout's north side, but under its south side.

Pont Abraham Interchange

Main Article: Pont Abraham Interchange

Pont Abraham is the westernmost motorway junction in Britain. Consisting of a roundabout with the A48 and A483, junction 49 is only one of two (junction 48 being the other one) motorway junctions signed with Welsh destinations first.

All junctions

Structures

Second Severn Crossing

Main Article: Second Severn Crossing

The Second Severn Crossing was constructed between 1992 and 1996 to provide relief for the Severn Bridge and Wye Bridge between England and Wales. Upon completion, the M4 moved across from the original bridges (which became part of the M48) to the new bridge.

Brynglas Tunnels

Main Article: Brynglas Tunnels

The Brynglas Tunnels are situated on the Newport bypass, between junctions 25a and 26. They are twin-bored tunnels, each carrying two traffic lanes and opened in 1967. Until recently, the eastbound tunnel was lit by orange lighting, the westbound by white. Both tunnels have overhead lane control signals for contraflow purposes.

Services

Heston services

Main Article: Heston services

Heston services are one of only two MSAs within the M25. They are located on a cramped site within Greater London, between junctions 2 and 3.

Chieveley services

Main Article: Chieveley services

These are situated where the M4 crosses the A34 near the village of Chieveley in Berkshire.

Leigh Delamere services

Main Article: Leigh Delamere services

Leigh Delamere services are located in Wiltshire between junctions 17 and 18. Originally, only the eastbound side was developed; the westbound side followed around ten years later.

Pont Abraham services

Main Article: Pont Abraham services

Pont Abraham services are a single-site MSA located on the western terminal roundabout of the M4, at junction 49. It is operated by RoadChef.

Traffic data

From http://www.dft.gov.uk/traffic-counts/

Link	2002 AADF	2006 AADF	2010 AADF	2014 AADF
J1-2	85937	90124	78182	93447
J2-3	95837	97379	85188	99632
J3-4	132852	133351	123890	129381
J4-4A	65318	71461	60418	59922
J4-A408	50783	43052	53909	52258
J4-4B	146092	143536	148143	159549
J4B-5	140319	144512	141194	146271
J5-6	135771	145431	128060	137696
J6-7	136395	125128	128356	124932
J7-A4	27369	28278	31309	32229
J7-8/9	139769	126506	133892	136613
J8/9-10	130353	129232	123557	126109
J10-11	123834	125859	117017	117587
J11-12	108780	122224	109193	105723
J12-13	90232	92102	86349	88807
J13-14	80802	83366	92727	83402
J14-15	80802	83366	92727	83402
J15-16	80474	86672	77290	77798
J16-17	67038	69764	69852	66812
J17-18	73967	78155	79457	70193
J18-19	79278	87907	85451	89253
J19-20	102913	107711	114949	119111
J20-21	53876	62682	60512	60787
J21-22	36805	43144	41665	42024
J22-23	55607	59472	62036	61144
J23-23A	67419	75935	71476	78770
J23A-24	72296	78821	83098	86222
J24-25	97161	104720	89804	101206
J25-25a	92393	96184	89062	110033
J25A-26	74213	77193	60186	80457
J26-27	101317	107891	107168	109620
J27-28	103039	111210	107226	113134
J28-29	98404	105764	97581	114617
J29-30	59821	64779	58683	70812
J30-32	75478	65230	61809	79623
J32-33	83553	94444	93820	99756
J33-34	78262	101443	99868	94257
J34-35	72719	77065	75313	82094
J35-36	60538	67396	65720	69251
J36-37	57605	64939	62182	69388
J37-38	52209	60872	62508	67295
J38-39	50994	63279	68452	69558*
J39-40	57856	67340	63881	72596*
J40-41	59008	64789	79473	56508
J41-42	60959	69214	75384	68382
J42-43	65682	71715	58313	79674
J43-44	69098	72067	80322	81629
J44-45	56084	65969	63298	68391
J45-46	57244	68748	69351	68359
J46-47	54720	64793	62318	64528
J47-48	43273	56293	48970	51721
J48-49	35264	38455	38945	44275

Miscellanea

The section of the M4 between junctions 19 and 23 has the the highest number of consecutive motorway-to-motorway junctions in the United Kingdom.
In 1999 a controversial bus lane was established on a 5.6-km stretch of the eastbound carriageway of the M4 between junction 3 and the start of the elevated section of the motorway near Brentford. Suspended in December 2010, it was re-instated temporarily for the duration of the 2012 London Olympics.

For detailed information about this topic, see CBRD Motorway Database: M4 Bus Lane

Links

M4

Projects

M4/Newport Southern Bypass

Junctions

Almondsbury Interchange • Aust Interchange • Awkley Interchange • Bray Interchange • Brentford Interchange • Caerleon Interchange • Cardiff West Interchange • Castleton Interchange • Cherry Lane Roundabout • Chieveley Interchange • Chiswick Roundabout • Coedkernew Junction • Coldra Interchange • Colnbrook Interchange • Concord Roundabout • Coryton Interchange • Cox Green Interchange • Cranford Parkway Interchange • Dock Way Junction • Earlswood Interchange • Glan Llyn Junction • Groes Interchange • Grove Park Interchange • Hambrook Interchange • Heathrow Interchange • Hendy Interchange • High Cross Interchange • Holyport Interchange • Huntercombe Spur • M4 J31 • Langley Roundabout • Llandarcy Interchange • Llangyfelach Interchange • Lon-Las Interchange • Magor Interchange • Malpas Interchange • Margam Interchange • Miskin Interchange • Newhouse • Pencoed Interchange • Penllergaer Interchange • Pentwyn Interchange • Pentyla Interchange • Pilning Interchange • Plough Hill Roundabout • Pont Abraham Interchange • Pyle Interchange • Rogiet Interchange • Sarn Interchange • Spittleborough Roundabout • Stanton St Quinton Roundabout • Taibach Interchange • The Thicket Roundabout • Theale Interchange • Three Mile Cross Interchange • Tormarton Interchange • Tredegar Park Interchange • Tuns Lane Interchange • Wickham Interchange • Winnersh Interchange • Ynysforgan Interchange

Services

Cardiff Gate services • Cardiff West services • Chieveley services • Heston services • Leigh Delamere services • Magor services • Maidenhead services • Membury services • Pont Abraham services • Port Talbot services • Pucklechurch services • Reading services • Sarn Park services • Swansea West services • Warren Copse services • Wilcrick services

Crossings

Brynglas Tunnels • Calcot Viaduct • Carters Hill Bridge • Chiswick Flyover • New Thames Bridge • Second Severn Crossing • Severn Bridge • Wye Bridge (Chepstow)

Roads

E30 • E105 (London - Fishguard) • Ffordd Cambria • Longest Lane • M4/Airport Spur

Places

Brentford • Bridgend • Bristol • Cardiff • Chippenham • London • Maidenhead • Neath • Newbury • Newport • Port Talbot • Reading • Slough • Swansea • Swindon

Related Pictures
View gallery (500)

Other nearby roads

London

NCN1 • NCN20 • NCN21 • A1 • A1(M) • A1/Sandbox • A2 • A2(M) (Kidbrooke - Falconwood) • A3 • A4 • A5 • A10 • A11 • A11(M) • A12 • A13 • A20 • A21 • A23 • A23(M) Provisional Allocation • A24 • A30 • A30/Sandbox • A40 • A41 • A101 • A127 • A216 • A233 • B269 • B519 • Balham Loop • E1 (Old System) • E2 (Old System) • E5 (Old System) • E8 (Old System) • E13 • E15 • E30 • E31 (via Carlisle) • E31 (via Newcastle) • E33 (London - Glasgow) • E105 (London - Fishguard) • E107 (London - Tilbury) • E108 (London - Southend) • East Cross Route • Ermine Street • EuroVelo 2 • EuroVelo 5 • Great North Road • Holyhead Road • London Inner Ring Road • Longest Lane • M1 • M3 • M11 • M12 (Brentwood - Chelmsford) • M12 (Woodford - Brentwood) • M12 (Woodford - Maplin) • M13 • M14 • M15 • M16 • M20 • M23 • M25 • M30 • M40 • M41 • M100 • NCN13 • NCN4 • Northern and Western Motorway • Orbital Tunnel Route • Ringway 2 • Ringway 3 • Ringway 4 • RM3 • South Cross Route • T1 (Britain) • T2 (Britain) • T3 (Britain) • T4 (Britain) • T5 (Britain) • T6 (Britain) • T8 (Britain) • T9 (Britain) • T10 (Britain) • T11 (Britain) • T12 (Britain) • T31 (Britain) • T32 (Britain) • T33 (Britain) • T34 (Britain) • T35 (Britain) • Watling Street

Reading

NCN23 • A4 • A32 • A33 • A42 (Reading - Birmingham) • A327 • A329 • A329(M) • A3031 (Reading) • A3045 (Berkshire) • A3290 • A4009 • A4074 • A4155 • B478 • B479 • B481 • B3031 • B3031 (Central Reading) • B3032 (Reading) • B3270 • B3345 • B3349 • B3350 • B3350 (Shinfield) • B4007 (Reading) • B4446 • B4526 • C100 (Reading) • C101 (Reading) • C102 (Reading) • C103 (Reading) • C104 (Reading) • C105 (Reading) • C106 (Reading) • C107 (Reading) • C200 (Reading) • C201 (Reading) • C202 (Reading) • C203 (Reading) • C204 (Reading) • C205 (Reading) • C206 (Reading) • C300 (Reading) • C301 (Reading) • C302 (Reading) • C303 (Reading) • C304 (Reading) • C400 (Reading) • C401 (Reading) • C402 (Reading) • C403 (Reading) • C404 (Reading) • C405 (Reading) • C406 (Reading) • C407 (Reading) • C408 (Reading) • C409 (Reading) • C410 (Reading) • C411 (Reading) • C500 (Reading) • C501 (Reading) • C502 (Reading) • C503 (Reading) • C504 (Reading) • C6601 (West Berkshire) • C6709 (West Berkshire) • C6710 (West Berkshire) • C6711 (West Berkshire) • C6712 (West Berkshire) • C6713 (West Berkshire) • E30 • E105 (London - Fishguard) • EuroVelo 2 • Hatfield - Reading Turnpike • Longest Lane • M31 • NCN4 • POLO • T9 (Britain)

Bristol

A4 • A36 • A37 • A38 • A369 • A370 • A403 • A407 (Bristol) • A420 • A430 (Chippenham - Bristol) • A431 • A432 • A3024 (Bristol) • A3029 • A3034 (Bristol) • A4017 • A4018 • A4032 • A4044 • A4162 • A4174 • A4175 • A4176 • A4320 • B3119 • B3120 • B3121 (Bristol) • B3122 • B3123 (Bristol) • B3124 • B3125 • B3126 • B3129 • B4045 (Keynsham) • B4046 • B4047 (Gloucestershire) • B4048 • B4049 • B4050 • B4051 • B4052 • B4053 • B4053 (Colston Street, Bristol) • B4054 • B4055 • B4056 • B4057 • B4058 • B4465 • B4466 • B4467 • B4468 • B4469 • E30 • E105 (London - Fishguard) • E116 (Old System) • EuroVelo 1 • EuroVelo 2 • Longest Lane • M5 • M32 • M49 • NCN4 • Outer Circuit Road • South Bristol Spur • T9 (Britain) • T16 (Britain)

Cardiff

A48 • A48(M) • A48(M) (Llantrisant Radial) • A469 • A470 • A4050 • A4053 (Cardiff) • A4054 • A4055 • A4056 • A4119 • A4160 • A4161 • A4232 • A4234 • B4239 • B4258 (Llandaff) • B4258 (Roath - Gabalfa) • B4259 • B4260 (Penarth) • B4261 • B4261 (Llandaff - Llantrisant) • B4262 • B4267 • B4288 (Monmouthshire) • B4487 • B4488 • B4562 • E30 • E105 (London - Fishguard) • Ffordd Cambria • Hook Road • NCN4 • NCN8 • T10 (Britain) • T75 (Britain) • Western Tangential

Swansea

A48(M) (Morriston Bypass) • A465 • A475 (Swansea - Carmarthen) • A483 • A484 • A4067 • A4068 (Morriston - Ystalyfera) • A4069 (Swansea) • A4070 • A4118 • A4216 • A4217 • A4230 • A4240 • B4247 • B4271 • B4290 • B4291 • B4292 • B4293 (Swansea) • B4294 (Gower) • B4295 • B4296 • B4433 • B4436 • B4489 • B4593 • B4603 • B4620 • B4625 • B5444 (Swansea) • E30 • E105 (London - Fishguard) • EuroVelo 1 • NCN4 • T10 (Britain) • T18 (Britain)

Motorways in Great Britain

Current Motorways

M1 • M2 • M3 • M4 • M5 • M6 • M6 Toll • M8 • M9 • M11 • M18 • M20 • M23 • M25 • M26 • M27 • M32 • M40 • M42 • M45 • M48 • M49 • M50 • M53 • M54 • M55 • M56 • M57 • M58 • M60 • M61 • M62 • M65 • M66 • M67 • M69 • M73 • M74 • M77 • M80 • M90 • M180 • M181 • M271 • M275 • M602 • M606 • M621 • M876 • M898
A1(M) • A3(M) • A8(M) • A14(M) • A38(M) • A48(M) • A57(M) • A58(M) • A64(M) • A66(M) • A74(M) • A92(M) • A167(M) • A168(M) • A194(M) • A195(M) • A308(M) • A329(M) • A404(M) • A601(M) • A627(M) • A635(M) • A666(M) • A823(M) • A1058(M)
Motorway Spurs • (M4 Heathrow Spur • M25 T5 Spur • Walton Summit M'way)

Former Motorways

M10 • M15 • M16 • M30 • M41 • M52 • M62 • M63 • M64 • M65 • M68 • M85 • M110 • M111 • M270 • M274 • M531 • M600
A2(M) • A4(M) • A5(M) • A8(M) • A11(M) • A18(M) • A20(M) • A21(M) • A23(M) • A36(M) • A40(M) (Central London) • A40(M) (Buckinghamshire) • A41(M) • A46(M) • A48(M) (Morriston) • A48(M) (Port Talbot) • A65(M) • A102(M) (North) • A102(M) (South) • A423(M) • A446(M) • A604(M) • A638(M) • A696(M) • A1231(M) • A6127(M) • A6138(M) • A6144(M)

Unbuilt Motorways

M4 Toll • M12 (Woodford - Brentford) • M12 (Woodford - Maplin) • M12 (Brentwood - -Chelmsford) • M13 • M17 • M19 • M31 • M58 • M59 • M60 • M62 RR • M64 • M81 • M82 • M83 • M100 • M272 • M601 • M650
A2(M) • A6(M) (West) • A6(M) (East) • A14(M) • A48(M) • A59(M) • A61(M) • A556(M) • A695(M)
A Ring • Bilston Link • Belmont Link • B-W M'way • CME Bypass • CMW • Central Spine • Chippenham Spur • Coventry N-S M'way • Cublington Airport M'way • Denham Spur • Derby Urban M'way • Droitwich-Leicester M'way • East Coast M'way • EXR • East Kilbride M'way • E-W Underground M'way • Eastern M'way • Euroroute • Friars Goose Xing • Furness Link • Glasgow IRR • GM Western Relief Road • Hamilton-Cumbernauld M'way • Hook Road • Johnstone M'way • Kendal Link • Liverpool Inner M'way • LOX M'way • Malvern Radial • Manchester IRR • Morecambe Link • NE Urban M'way • NXR • N&W M'way • Paisley-Hamilton M'way • POLO • Princess P'way M'way • Reading Urban M'way • Ringway 2 • Sheffield Spur • S Bristol Spur • SCRPDR • SXR • Stirling Corner Link • Strensham-Solihill M'way • Strensham-Solihill M'way • TGAAR • Townhill Link • Trafford Park M'way • Warndon Radial • Watford Urban M'Way • Western Orbital • Weston Spur

M4

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