The M4: where people are seriously hurt
Over 2021–2025, 262 people were killed or seriously injured in 207 collisions on the M4, making it the 39th worst numbered road in Britain by that measure.
207
serious or fatal collisions
262
people killed or seriously injured
36
collisions that took a life
#39
of 150 numbered roads
What the record shows
The M4 carries 1,152 recorded injury collisions over the period, 207 of them serious or fatal. Serious injury concentrates in West Berkshire, Hillingdon, Wiltshire, with 3 further areas also recording collisions. Collisions here are more likely than average to be fatal: 17% against 7% across the numbered network, which usually points to higher speeds. Most collisions were recorded on 70 mph sections. The worst year of the period was 2025 with 55 serious collisions, and the count is up 67% between 2021 and 2025.
Every serious and fatal collision on the M4
Blue markers are serious collisions, red crosses fatal. Click any marker for the year. Zoom in to see the specific junctions and stretches where they cluster.
Where along the route
- West Berkshire26 KSI
- Hillingdon24 KSI
- Wiltshire18 KSI
- Newport17 KSI
- South Gloucestershire15 KSI
- Hounslow15 KSI
Local authority areas with the most serious collisions on this road.
The trend
Serious and fatal collisions on the M4
2025: 55 (up 41% on the year before) · peak 55 in 2025 · +66.7% across the period
Axis clipped to the data range to show year-on-year movement.
About the M4
How many accidents happen on the M4?
Police recorded 1,152 injury collisions on the M4 over 2021–2025, of which 207 were fatal or serious. Those serious collisions left 262 people killed or seriously injured, including 36 fatal collisions.
Is the M4 a dangerous road?
By volume of serious injury it ranks 39 of the 150 numbered roads we analyse, and 5 among motorways. That is a count rather than a rate: longer and busier roads accumulate more collisions, so a high ranking reflects exposure as well as risk.
Where on the M4 do collisions happen?
They concentrate in West Berkshire, Hillingdon, Wiltshire. The map on this page plots every serious and fatal collision recorded on the route, so you can see the specific stretches rather than the total.
Counts include every collision the police recorded on this road number across all authority areas. They are not adjusted for traffic volume or road length, so treat them as a measure of where injury concentrates rather than a per-mile risk rating. Method. Free to reuse with attribution to this page.
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