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M4 J21 traffic

No incidents reported at M4 J21 right now.

Updated 03:28 UK time · at J21 and the stretches either side

View on the live map All M4 traffic

Right now

Nothing reported at M4 J21 at the moment.

Closures tonight

No closures planned at J21 tonight.

The last 90 days

Incidents

17

Collisions

1

Road closed

14times

Typical time to clear

6 h 8 minmedian of 16

Busiest time

20:00–21:00

Recent incidents

M4 crash J20–J21 westboundSat 08:53 · cleared after 44 min
M4 closed J20–J21 westbound27 Oct 2026 04:00 · cleared after 1 h 36 min
M4 closed J20–J21 westbound24 Oct 2026 15:12 · cleared after 12 h 24 min
M4 closed J19–J20 westbound23 Oct 2026 14:24 · cleared after 5 h 22 min
M4 closed J20–J21 westbound23 Oct 2026 12:44 · cleared after 2 h 44 min
M4 closed J20–J21 westbound21 Oct 2026 20:45 · cleared after 6 h 52 min
M4 closed J20–J21 westbound20 Oct 2026 21:17 · cleared after 7 h 26 min
M4 closed J19 westbound12 Oct 2026 07:57 · cleared after 4 h 56 min
M4 closed J20–J21 westbound6 Oct 2026 20:27 · cleared after 7 h 37 min
M4 closed J20–J21 westbound5 Oct 2026 20:22 · cleared after 7 h 44 min
M4 closed J20–J21 westbound30 Sept 2026 19:43 · cleared after 9 h 52 min
M4 closed J20–J21 westbound28 Sept 2026 20:56 · cleared after 49 h 39 min
M4 closed J20–J21 westbound27 Sept 2026 19:52 · cleared after 9 h 23 min
M4 closed J20–J21 westbound26 Sept 2026 22:43 · cleared after 6 h 8 min
M4 closed J20–J21 westbound26 Sept 2026 20:08 · cleared after 2 h 17 min

Junctions either side

Every M4 junction

Common questions

Is the M4 closed at junction 21 right now?

No incidents have closed it right now.

Is M4 J21 closed tonight?

No closures are planned at J21 tonight.

How many crashes have there been at M4 J21?

1 collision reported at or either side of J21 in the last 90 days, the latest on 31 Oct 2026 at 08:53.

Includes incidents at J21 and on the stretches either side of it. Sources: National Highways, TomTom, TfL and Traffic Wales. Times are UK time.