M4 motorway

M4
M4
	Prince of Wales Bridge looking towards Wales
Route information
	Part of
	Maintained by ; Highways England; South Wales Trunk Road Agent
Length	189 mi (304 km)
Existed	1963–present
History	Opened: 1959 (Chiswick Flyover), 1961 (as A4(M)), 1963, 1966 (as A48(M)); Completed: 1996
Major junctions
East end	Chiswick; 51°29′23″N 0°16′41″W / 51.4897°N 0.2781°W
	; J4b → M25 motorway; /; J8/9 → A308(M) motorway/A404(M) motorway; ; J10 → A329(M) motorway; ; J19 → M32 motorway; ; J20 → M5 motorway; ; J21 → M48 motorway; ; J22 → M49 motorway; ; J23 → M48 motorway; ; J29 → A48(M) motorway
To	Pont Abraham; 51°44′42″N 4°03′54″W / 51.7451°N 4.0651°W
Location
Country	United Kingdom
Counties	Greater London, Berkshire, Wiltshire, Gloucestershire, Monmouthshire, Newport, Cardiff, Vale of Glamorgan, Rhondda Cynon Taf, Bridgend, Neath Port Talbot, Swansea, Carmarthenshire
Primary; destinations	; London; London Heathrow Airport; Slough; Maidenhead; Reading; Newbury; Swindon; Bristol; Newport; Cardiff; Bridgend; Port Talbot; Neath; Swansea
Road network
	Roads in the United Kingdom; Motorways; A and B road zones;

The M4 is a long motorway in the United Kingdom. It goes from London to South Wales. It also passes Bristol. It was first called the London–South Wales Motorway.

Junctions[change | change source]

mile	km	Eastbound exits (B carriageway)	Junction	Westbound exits (A carriageway)
M4 motorway
7.3	11.8	Road continues as A4 to Central London	J1 ^{[coord 1]}	Start of motorway
8.3 8.5	13.4 13.7	North Circular A406 South Circular A205 Chiswick A315	J2	Staines, Hounslow, Brentford A4
12.5 12.8	20.1 20.6	Heston services	Services	Heston services
13.4 13.7	21.5 22.1	Heathrow (Terminals 4, 5 & Cargo), Hayes, Harrow, Hounslow A312	J3	Heathrow (Terminals 4, 5 & Cargo), Hayes, Harrow, Hounslow A312
15.2 15.7	24.5 25.2	Heathrow (Terminals 2 & 3) (A4) Uxbridge A408	J4a	Heathrow (Terminals 2 & 3) (A4) Uxbridge A408
16.8 17.7	27.0 28.5	Heathrow (Terminals 4, 5 & Cargo) , Gatwick Airport , Watford (M3), (M23), (M40), (M1) M25	J4b ^{[coord 2]}	Heathrow (Terminals 4, 5&Cargo), Gatwick, Watford (M3), (M23), (M40), (M1), M25
19.1 19.5	30.7 31.4	Colnbrook, Langley, Slough (East) A4 Eton, Datchet B470	J5	Colnbrook, Langley, Slough (East) A4, Datchet B470
22.9 23.2	36.8 37.4	Slough (Central) A355 Windsor A322	J6	Slough (Central) A355 Windsor A322
24.7 25.0	39.8 40.3	Slough (West) A4	J7	Slough (West) A4
27.8 28.2	44.7 45.4	High Wycombe, Henley A404(M) Maidenhead A308(M)	J8/9	High Wycombe, Henley A404(M) Maidenhead A308(M)
35.0 35.8	56.4 57.6	Reading (East), Wokingham, Bracknell A329(M)	J10	Reading (East), Wokingham, Bracknell A329(M)
40.6 41.2	65.4 66.3	Basingstoke, Reading (Central & South) A33	J11	Basingstoke, Reading (Central & South) A33
43.5 43.8	70.0 70.5	Reading services	Services	Reading services
45.3 45.7	72.9 73.5	Reading (West), Theale A4	J12	Reading (West), Theale A4
56.9 57.2	91.5 92.1	Newbury, Oxford A34 Chieveley services (Moto)	J13 Services ^{[coord 3]}	Newbury, Oxford A34 Chieveley services (Moto)
64.4 64.8	103.7 104.3	Hungerford, Wantage A338	J14	Hungerford, Wantage A338
68.7	110.5	Membury services	Services	Membury services
76.4 77.1	122.9 124.0	Swindon (East) A419 Marlborough A346 Oxford (A420)	J15	Swindon A419, Marlborough A346
82.4 82.8	132.6 133.2	Swindon (West), Royal Wootton Bassett, Wroughton, MoD Lyneham, Calne A3102	J16	Swindon (West), Royal Wootton Bassett, Wroughton, MoD Lyneham, Calne A3102
94.8 95.3	152.5 153.4	Chippenham A350 Cirencester A429	J17	Chippenham A350 Cirencester A429
96.7	155.7	Leigh Delamere services	Services	Leigh Delamere services
104.9 105.6	168.8 170.0	Bath, Stroud A46	J18	Bath, Stroud A46
112.8 113.2	181.5 182.1	Bristol M32	J19	Bristol M32
115.8 116.3	186.3 187.2	The SOUTH WEST, Bristol (West), The MIDLANDS, Gloucester, Bristol Airport , M5	J20 Almondsbury Interchange ^{[coord 4]}	The SOUTH WEST, Bristol (West) M5(S) The MIDLANDS, Gloucester M5(N)
117.7 189.5	189.5 190.0	No access	J21	Chepstow M48
121.3 121.6	195.2 195.7	Avonmouth M49	J22	Avonmouth M49
121.7 124.1	195.9 199.8	Entry into England	Second Severn Crossing ^{[coord 5]}	Entry into Wales
127.0	204.4	No toll plaza	Bridge Toll	Former Toll plaza (closed Dec 2018)
129.2	208.0	Chepstow M48	J23	No access
131.4 132.2	211.4 212.8	Magor, Caldicot A4810 Magor services	J23A Services	Magor, Caldicot A4810 Magor services
134.8 135.6	217.0 218.3	City centre A48 Newport (East) B4237 Monmouth A449 The MIDLANDS (M50)	J24	City centre A48 Newport (East) B4237 Monmouth A449
137.9	222.0	No access	J25	Caerleon B4596
138.3	222.6	No access	J25A	Newport, Cwmbran A4042
138.8 139.1	223.4 223.8	Brynglas Tunnels	Tunnel	Brynglas Tunnels
139.1 139.5	223.8 224.5	Newport, Cwmbran, Caerleon A4051	J26	Newport A4051
140.8 141,4	226.6 227.6	High Cross B4591	J27	High Cross B4591
142.0 142.9	228.5 230.0	Newport A48 Risca, Brynmawr A467	J28	Newport A48 Risca, Brynmawr A467
143.6	231.1	No access	J29	Cardiff (East and South) A48(M)
146.6 147.3	236.0 237.0	Cardiff (East) A4232 Cardiff Gate services	J30 Services	Cardiff (East) A4232 Cardiff Gate services
151.9 244.5	244.5 246.1	Merthyr Tydfil, Cardiff A470	J32	Cardiff (North), Merthyr Tydfil A470
155.4 156.0	250.1 251.1	Cardiff (West), Barry, Penarth A4232 Cardiff Airport Cardiff West services	J33 Services	Cardiff (West), Barry, Penarth A4232 Cardiff Airport Cardiff West services
157.5 158.1	253.5 254.4	Llantrisant, Rhondda A4119 Royal Glamorgan Hospital	J34	Llantrisant, Rhondda A4119 Royal Glamorgan Hospital
163.9 164.4	263.7 264.5	Pen-coed A473	J35	Bridgend, Pen-coed A473
167.5 168.3	269.6 270.8	Bridgend A4061 Maesteg A4063 Princess of Wales Hospital Sarn Park services	J36 Services	Bridgend A4061 Maesteg A4063 Princess of Wales Hospital Sarn Park services
172.8 173.5	278.1 279.3	Pyle, Porthcawl A4229	J37	Porthcawl, Pyle A4229
177.0 177.3	284.9 285.3	Port Talbot A48	J38	Port Talbot A48
178.3	286.9	No access (on-ramp only)	J39	No access
179.7 179.9	289.2 289.6	Port Talbot A4107	J40	Port Talbot A4107
180.9 181.3	291.1 291.8	Port Talbot A48	J41	Briton Ferry A48
183.9 184.9	295.9 297.3	Briton Ferry A48 Swansea (South) A483	J42	Swansea (South) A483
184.9 185.7	297.5 298.8	Neath, Merthyr Tydfil A465	J43	Neath, Merthyr Tydfil A465
187.0 187.4	300.9 301.6	Swansea (East) A48	J44	Swansea (East) A48
188.8 189.3	303.9 304.7	Pontardawe, Swansea (North) A4067	J45	Pontardawe, Swansea (North) A4067
190.8 191.4	307.0 308.0	Llangyfelach B4489 Felindre Morriston Hospital	J46	Llangyfelach B4489 Felindre Morriston Hospital
192.4 193.1	309.6 310.7	Swansea (West) A483 Gorseinon A48 Swansea services	J47 Services	Swansea (West) A483 Gorseinon A48 Swansea services
196.4 197.1	316.0 317.2	Pontarddulais, Llanelli A4138	J48	Pontarddulais, Llanelli A4138
199.2	320.6	Start of motorway	J49 Terminus Services ^{[coord 6]}	Motorway terminates at a roundabout: Carmarthen A48 Ammanford, Llandeilo A483 Pontarddulais A48 Pont Abraham services
1.000 mi = 1.609 km; 1.000 km = 0.621 mi Incomplete access Tolled