M4 closed J20–J21 westbound

Road closure on the M4 westbound at J20–J21 on Monday 28 September 2026, from 20:56. Cleared at 22:35 after 49 h 39 min. Timeline of reports from TomTom and National Highways.

Status

Cleared 22:35 on 30 Sept 2026, after 49 h 39 min

Location

M4 westbound · J20–J21

Reported as

Road closed

Lanes

Road closed

Sources

TomTom ×3 · National Highways

Timeline

1. Mon 20:56 National Highways: road closed
2. Mon 21:01 TomTom: queueing traffic, “Slow traffic, Lane closed”, delay ~3 min
3. Mon 21:02 TomTom no longer reports it
4. Mon 21:02 All clear: no source reports it any more
5. Mon 21:56 TomTom: queueing traffic, “Slow traffic”, delay ~4 min
6. Mon 22:19 TomTom no longer reports it
7. Mon 22:32 TomTom: road closed
8. Mon 23:09 TomTom: “Bridge closed”
9. Tue 04:07 TomTom no longer reports it
10. Tue 04:41 National Highways: road reopened
11. Tue 04:41 All clear: no source reports it any more
12. Wed 21:49 TomTom: road closed (reported again)
13. Wed 22:35 TomTom: still reported after more than 48 hours, so treated as out of date
14. Wed 22:35 All clear: no source reports it any more

Source reports

• Slow traffic, Lane closed
• M4 westbound between J20 and J21
• Slow traffic
• Closed

Other recent incidents on the M4

• M4 crash J18–J19yesterday 17:45 · cleared after 3 h 12 min
• M4 reported crash J19–J20 westboundyesterday 17:27 · cleared after 1 h 26 min
• M4 crash Both directionsyesterday 08:08 · cleared after 1 h 5 min
• M4 stopped traffic J3 westboundyesterday 06:48 · cleared after 3 h 3 min
• M4 crash J6 westboundWed 15:41 · cleared after 1 h 35 min
• M4 crash J10–J8 eastboundWed 07:50 · cleared after 2 h 6 min
• M4 stopped traffic J20–J21Wed 07:29 · cleared after 1 h 23 min
• M4 stopped traffic J4–J3 eastboundWed 06:44 · cleared after 3 h 3 min
• M4 crash J18Tue 19:23 · cleared after 46 min
• M4 crash J5–J4B eastboundTue 18:15 · cleared after 57 min

Live traffic and past incidents at M4 J20 and M4 J21.

The sources don't report causes or injuries, so neither does this page. Times are UK time. For alerts, follow @motorways.me on Bluesky.