Historical data · DfT STATS19 · 2021–2025
M4 Accident History
Quick answer: 1,152 injury collisions were recorded on the M4 from 2021 to 2025, 36 of them fatal and 171 serious. M4 Motorway (London – South Wales) — recorded crashes only, not a measure of risk.
1,152
Recorded collisions
2021–2025
207
Fatal or serious
36 fatal
1,746
Casualties
40 killed
70
Motorcyclist casualties
5 years
Covered road section
Where the recorded collisions were
STATS19 first_road_class = 1 (motorway) and first_road_number = 4; A4(M) sections and collisions where the motorway is only the second road are not included. map points are fatal and serious collisions only; hexagons (Uber H3, about 5 km²) hold every recorded collision with coordinates.
M4 route (simplified) Fatal collision Serious collisionHexagon shade = recorded count, not risk
Annual counts
M4 by year
| Year | Collisions | Fatal | Serious | Slight | Casualties | Killed | Pedestrian casualties | Cyclist casualties | Motorcyclist casualties | Car occupant casualties | Other casualties |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2025 | 252 | 4 | 51 | 197 | 385 | 5 | 2 | 0 | 23 | 301 | 59 |
| 2024 | 216 | 8 | 31 | 177 | 306 | 8 | 3 | 0 | 13 | 244 | 46 |
| 2023 | 220 | 7 | 32 | 181 | 359 | 9 | 3 | 0 | 11 | 303 | 42 |
| 2022 | 226 | 6 | 35 | 185 | 339 | 7 | 3 | 0 | 10 | 295 | 31 |
| 2021 | 238 | 11 | 22 | 205 | 357 | 11 | 5 | 0 | 13 | 297 | 42 |
| Total | 1,152 | 36 | 171 | 945 | 1,746 | 40 | 16 | 0 | 70 | 1,440 | 220 |
Period comparison
2021–2022 compared with 2024–2025
Yearly averages of recorded counts. A change can come from traffic volumes, roadworks or recording changes as well as safety — the data cannot separate them.
| Measure | Average per year 2021–2022 | Average per year 2024–2025 | Change |
|---|---|---|---|
| Collisions | 232.0 | 234.0 | +0.9% |
| Fatal | 8.5 | 6.0 | -29.4% |
| Serious | 28.5 | 41.0 | +43.9% |
| Casualties | 348.0 | 345.5 | -0.7% |
| Pedestrian casualties | 4.0 | 2.5 | -37.5% |
| Motorcyclist casualties | 11.5 | 18.0 | +56.5% |
Casualties by road user
Chart data as a table
| Road user | Casualties |
|---|---|
| Pedestrian | 16 |
| Cyclist | 0 |
| Motorcyclist | 70 |
| Car occupant | 1,440 |
| Other | 220 |
Month of year
Chart data as a table
| Month | Collisions |
|---|---|
| January | 93 |
| February | 82 |
| March | 92 |
| April | 91 |
| May | 101 |
| June | 85 |
| July | 105 |
| August | 97 |
| September | 93 |
| October | 104 |
| November | 123 |
| December | 86 |
Hour of day
Chart data as a table
| Hour | Collisions |
|---|---|
| 0:00 | 25 |
| 1:00 | 9 |
| 2:00 | 19 |
| 3:00 | 14 |
| 4:00 | 19 |
| 5:00 | 24 |
| 6:00 | 30 |
| 7:00 | 66 |
| 8:00 | 78 |
| 9:00 | 49 |
| 10:00 | 48 |
| 11:00 | 52 |
| 12:00 | 63 |
| 13:00 | 61 |
| 14:00 | 63 |
| 15:00 | 72 |
| 16:00 | 93 |
| 17:00 | 98 |
| 18:00 | 67 |
| 19:00 | 53 |
| 20:00 | 44 |
| 21:00 | 37 |
| 22:00 | 34 |
| 23:00 | 34 |
Day of week
Chart data as a table
| Day | Collisions |
|---|---|
| Monday | 132 |
| Tuesday | 184 |
| Wednesday | 161 |
| Thursday | 168 |
| Friday | 218 |
| Saturday | 153 |
| Sunday | 136 |
Local authorities
Where along the M4 collisions were recorded
| Local authority | Collisions 2021–2025 |
|---|---|
| Hillingdon | 157 |
| West Berkshire | 134 |
| South Gloucestershire | 101 |
| Wiltshire | 101 |
| Slough | 100 |
| Newport | 78 |
| Windsor and Maidenhead | 65 |
| Hounslow | 63 |
| Swindon | 55 |
| Cardiff | 48 |
| Bridgend | 40 |
| Neath Port Talbot | 39 |
| Swansea | 38 |
| Wokingham | 29 |
| Carmarthenshire | 25 |
Speed limit at the collision site
Recorded speed limits
| Speed limit | Collisions |
|---|---|
| 70 mph | 799 |
| 50 mph | 161 |
| 40 mph | 100 |
| 60 mph | 55 |
| 30 mph | 35 |
| 20 mph | 2 |
Source and limitations
About this data
- Source: Department for Transport, Road Safety Data (STATS19), police-reported personal injury collisions in Great Britain — Open Government Licence v3.0. Prepared 2026-09-13.
- Matching: STATS19 first_road_class = 1 (motorway) and first_road_number = 4; A4(M) sections and collisions where the motorway is only the second road are not included.
- Counts are police-reported collisions with at least one injured casualty; damage-only crashes are not in STATS19.
- A collision is counted once; casualties are counted from the casualty table.
- Changes between years can reflect reporting changes (for example police forces moving to the CRASH reporting system) as well as real change.
- Hexagons are Uber H3 cells; a busy cell is not a measure of risk because traffic volumes are not included.
- The route line on the map is a simplified sketch of the corridor; crashes are placed at the coordinates the source recorded.
- Download (CSV): yearly counts · counts by local authority · mapped fatal and serious collisions — more datasets on the download data page.
Live incidents and today's reports: M4 live page · historical hotspots in Great Britain · compare accident trends · all roads · methodology
Questions
M4 accident history — FAQ
Where does the M4 accident history come from?
From the Department for Transport's STATS19 road safety data: police-reported collisions in which at least one person was injured. A collision is counted for the M4 when STATS19 records the motorway as its first road. Damage-only collisions are not in STATS19.
Is the M4 getting more dangerous?
These are counts, not rates. The data does not include how much traffic used the road each year, so a rise or fall can reflect traffic growth, roadworks, reporting changes (several police forces moved to the CRASH recording system) or real change. The yearly table above shows the recorded numbers without drawing that conclusion for you.
Why might a crash near the M4 be missing?
STATS19 first_road_class = 1 (motorway) and first_road_number = 4; A4(M) sections and collisions where the motorway is only the second road are not included. Crashes on slip roads or local roads next to it can be recorded under another road.
Which year had the most recorded collisions on the M4?
2025, with 252 recorded collisions. The fewest were in 2024 (216). These are counts for 2021–2025, not rates, so a busier year on the road can record more without the road being less safe.
When do most recorded collisions on the M4 happen?
The busiest hour in the records is 17:00–17:59 (8.5% of collisions with a recorded time), the busiest day is Friday and the busiest month is November. The data holds no traffic volumes, so these peaks show when crashes were recorded, not when driving there is riskiest.
Which council area records the most collisions on the M4?
Hillingdon, with 157 recorded collisions (14.6% of the total). Longer sections of road inside one council area naturally record more, so this is not a ranking of danger.
Can I download the M4 accident data?
Yes. The yearly counts, the counts by local authority and the mapped crash points can each be downloaded as CSV from the Source and limitations section of this page, with the source and licence written into the file.
Is this live?
No — this is historical data (2021–2025) published once a year. Live incidents and today's reports for the M4 are on the road's live page.