M4 motorway
|
mile
|
km
|
Eastbound exits (B carriageway)
|
Junction
|
Westbound exits (A carriageway)
|
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
|