Live M4 Traffic Flow Map Now
How fast is the M4 moving right now? This live traffic flow map shows the speed on every stretch of the M4 from Junction 1 at Chiswick in west London to Junction 23 near the Severn crossings, in both directions. Green is moving freely, amber is slow and red is very slow or stopped.
The map is a summary. For the full picture before you set off, see all the latest M4 traffic news, the overhead message signs showing on the M4 right now, and the speed limits on the overhead signs.
Untick all three to see just the speeds. We show the important overhead signs and the mandatory speed limits (red ring); see every overhead sign.
NOTE: The speed flow, overhead sign messages or other information shown on our live traffic speed flow map is updated every few minutes. We cross check the data and aim to provide warnings if there could be a delay or an inaccurate speed reading. There can be occasions, beyond our control, and despite our best efforts where the speed flow could be inaccurate. We cannot therefore guarantee the speed you can expect on any stretch of the motorway is always accurately shown. However we hope you will find our live traffic speed flow map a useful tool in trying to plan your journey. Safe driving.
How to read the M4 speed flow map
West is at the top, so the Severn crossings are at the top of the map and London at the bottom. The left-hand line is the westbound carriageway, towards Bristol and Wales, and the right-hand line is eastbound, towards London. The map stops at Junction 23 because the M4 in Wales is run by the Welsh Government and is not in National Highways’ speed data. Junctions are spaced by the real distance between them, and the miles between each pair are shown on the left. Tap or click any stretch to see its speed and how recently it was measured.
The part of the M4 on this map is about 118 miles long, so use Show junctions to see only the part you are about to drive, and Colour the road by to switch between plain speed in miles per hour and speed compared with what is normal for that stretch at this time of day.
Services and connecting motorways
A red end on a junction sign with a knife, fork and fuel pump marks services. Connecting motorways, such as the M25 at Junction 4B, the A329(M) at Junction 10, the M32 at Junction 19, the M5 at Junction 20, the M48 at Junctions 21 and 23 and the M49 at Junction 22, are shown in blue. Where we run a site for that motorway, a pointing hand shows the way you turn off; tap it to see that motorway’s site.
For every junction with the roads and places it serves, see the map of the M4 junctions.
Where the speeds come from
The speeds come from National Highways’ traffic data, which combines road sensors with vehicle data, and the map is refreshed every five minutes. Where no recent measurement is available for a stretch, the map shows the speed that is normal there at this time of day and says so when you tap it. Road closures reported by National Highways are shown in red with white crosses. Always follow the signs and signals you can see on the road.