The A4: where people are seriously hurt
Over 2021–2025, 553 people were killed or seriously injured in 507 collisions on the A4, making it the 8th worst numbered road in Britain by that measure.
507
serious or fatal collisions
553
people killed or seriously injured
34
collisions that took a life
#8
of 150 numbered roads
What the record shows
The A4 carries 2,597 recorded injury collisions over the period, 507 of them serious or fatal. Serious injury concentrates in Westminster, Hounslow, Slough, with 3 further areas also recording collisions. Its fatal share, 7%, sits close to the 7% average for the numbered network. Most collisions were recorded on 30 mph sections. The worst year of the period was 2025 with 116 serious collisions, and the count is up 38% between 2021 and 2025.
Every serious and fatal collision on the A4
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
- Westminster109 KSI
- Hounslow96 KSI
- Slough43 KSI
- Wiltshire43 KSI
- Bristol, City of42 KSI
- West Berkshire37 KSI
Local authority areas with the most serious collisions on this road.
The trend
Serious and fatal collisions on the A4
2025: 116 (up 16% on the year before) · peak 116 in 2025 · +38.1% across the period
Axis clipped to the data range to show year-on-year movement.
About the A4
How many accidents happen on the A4?
Police recorded 2,597 injury collisions on the A4 over 2021–2025, of which 507 were fatal or serious. Those serious collisions left 553 people killed or seriously injured, including 34 fatal collisions.
Is the A4 a dangerous road?
By volume of serious injury it ranks 8 of the 150 numbered roads we analyse, and 8 among a roads. 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 A4 do collisions happen?
They concentrate in Westminster, Hounslow, Slough. 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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