LIVEIncidentM4 J22 westbound access — Lane closures22:25 (10:25pm)LIVEIncidentM4 eastbound within J4B — Lane closures22:25 (10:25pm)LIVERoadworksM4 eastbound between J17 and J16 — Hard shoulder closed22:20 (10:20pm)LIVERoadworksM4 eastbound between J15 and J14 — Lane closures22:20 (10:20pm)LIVERoadworksM4 eastbound between J15 and J14 — Lane closures22:20 (10:20pm)See all the latest news →LIVEIncidentM4 J22 westbound access — Lane closures22:25 (10:25pm)LIVEIncidentM4 eastbound within J4B — Lane closures22:25 (10:25pm)LIVERoadworksM4 eastbound between J17 and J16 — Hard shoulder closed22:20 (10:20pm)LIVERoadworksM4 eastbound between J15 and J14 — Lane closures22:20 (10:20pm)LIVERoadworksM4 eastbound between J15 and J14 — Lane closures22:20 (10:20pm)See all the latest news →
50M4 EASTBOUND BETWEEN J5 & J4B4 signalsset 22:19 (10:19pm)Overhead MessageM4 J21-J23 CLOSED20 signsset 21:45 (9:45pm)50M4 EASTBOUND AT J4B1 signalset 22:16 (10:16pm)Overhead MessageM4 BRIDGE CLOSED1 signset 20:45 (8:45pm)40M4 EASTBOUND AT J4B1 signalset 22:16 (10:16pm)Overhead MessageM4 CLOSED USE M481 signset 20:45 (8:45pm)Overhead MessageM4 BRIDGE CLOSED USE M481 signset 20:45 (8:45pm)Overhead MessageM4 BRIDGE CLOSED ALL SOUTH WALES TRAFFIC - USE M481 signset 20:45 (8:45pm)See all the overhead messages →See all the speed limit signs →50M4 EASTBOUND BETWEEN J5 & J4B4 signalsset 22:19 (10:19pm)Overhead MessageM4 J21-J23 CLOSED20 signsset 21:45 (9:45pm)50M4 EASTBOUND AT J4B1 signalset 22:16 (10:16pm)Overhead MessageM4 BRIDGE CLOSED1 signset 20:45 (8:45pm)40M4 EASTBOUND AT J4B1 signalset 22:16 (10:16pm)Overhead MessageM4 CLOSED USE M481 signset 20:45 (8:45pm)Overhead MessageM4 BRIDGE CLOSED USE M481 signset 20:45 (8:45pm)Overhead MessageM4 BRIDGE CLOSED ALL SOUTH WALES TRAFFIC - USE M481 signset 20:45 (8:45pm)See all the overhead messages →See all the speed limit signs →
Live M4 traffic data from National Highways · updated 22:27 (10:27pm) Wed 21 Oct 2026
M4
Map of M4 Junctions 23 to 33: Newport and Cardiff
Over the Severn the M4 runs through Monmouthshire past Magor and Caldicot, round the north of Newport and through the Brynglas tunnels, then on past Castleton to the north of Cardiff, where the A470 runs down into the city at Coryton.
Cardiff and Newport commuters, visitors to the Celtic Manor and families heading up the valleys use this stretch. There are services at Magor, Cardiff Gate and Cardiff West. National Highways' live data stops at junction 23, so the map on this page shows the road, the towns and the junctions, but no live speeds yet.
Tap any junction number on the map to open that junction’s own page, with its close-up map and the places around it.
Showing live speeds westbound. The map shows one direction at a time; tap the other button to switch. For both directions side by side, with every sign and incident, see the live M4 speed flow map.
Driving Junction 23 to Junction 33: Distances and Times
From junction 23 to junction 33 is about 25 miles along the M4, about 21 minutes at the 70 mph speed limit in clear traffic. Here it is junction by junction; tap a junction to open its own page.
Distances are measured along the motorway between the centres of the junctions, from OpenStreetMap, and rounded to the nearest half mile. Times are at a steady 70 mph and do not allow for joining, leaving, roadworks or lower speed limits.
M4traffic.co.uk is dedicated to the latest M4 traffic news, checked every five minutes, 24 hours a day. The M4 meets the M25 at Junction 4b near Heathrow and the M5 near Bristol — see M25 Traffic and M5 Traffic.M4traffic.co.uk is dedicated to the latest M4 traffic news, checked every five minutes, 24 hours a day. The M4 meets the M25 at Junction 4b near Heathrow and the M5 near Bristol — see M25 Traffic and M5 Traffic.
