A woman in her thirties died on the M4 westbound between junctions 8/9 and 10 on 9 September. No arrests, and Thames Valley Police wants dashcam footage.
Thames Valley Police is appealing for witnesses to a fatal M4 crash west of Maidenhead, in which a woman in her thirties died on Wednesday night. The force has asked anyone who drove that stretch to check their dashcam footage.
The force published its appeal at 2.31pm on Thursday 10 September. It places the collision on the westbound carriageway between junctions 8/9 and 10, at around 9pm on Wednesday 9 September.
No arrests have been made.
What the force has said
Thames Valley Police’s statement is short and specific. It describes two separate collisions, minutes apart, on opposite carriageways.
- On the westbound carriageway, a white Mercedes 220 and a white Scania heavy goods vehicle collided.
- Shortly after, a second collision happened on the eastbound carriageway, involving a grey Kia Sorento.
- The driver of the Mercedes, a woman in her thirties, died at the scene. Her next of kin have been informed.
- No arrests have been made at this time.
The force has not named her, so neither do we.
Detective Sergeant Lyndsey Blackaby of the Serious Collision Investigation Unit is the investigating officer. In the appeal she said: “Firstly, our thoughts are with the family and friends of the deceased at this extremely difficult time.”
She added: “I also ask any drivers who were in the area at the time and have dashcam footage to review it, as it may contain important information about the collision or the moments leading up to it.”
If you were on that stretch of the M4
Anyone who was on the M4 between junctions 8/9 and 10 on the evening of Wednesday 9 September can help three ways.
- Upload footage through the force’s collision appeal portal.
- Report what you saw by calling 101 or using the force’s website, quoting reference 43260470931.
- Pass information anonymously to Crimestoppers on 0800 555 111 or through its website. The force offers this route in the same appeal, for anyone who would rather not give their name.
The appeal covers drivers who were in the area but have not yet spoken to the police, not only people who saw the collision itself.
Where this happened, and whose stretch it is
The force has given no location more precise than “between junctions 8/9 and 10”. That is a long way: junction 8/9 is Maidenhead’s, where the A404(M) and A308(M) leave the motorway, and junction 10 is out at Winnersh in Wokingham.
The stretch straddles the Royal Borough’s western boundary. The Department for Transport’s own collision records put Royal Borough incidents on the M4 as far west as roughly halfway between the two junctions, so part of it is in the borough and the rest is not. Whether this collision falls inside the boundary is not something the published record answers.
What the record shows about roads here
We looked at the Department for Transport’s collision file for the last five years, filtered to the Royal Borough of Windsor and Maidenhead.
Between 2021 and 2025 the police recorded 885 collisions in the borough, causing 1,050 casualties. Of those collisions, 8 were fatal, 177 serious and 700 slight.
The year-by-year totals were 176, 195, 189, 149 and 176. The number in which somebody was killed or seriously injured went 33, 37, 43, 27, 45. So the volume of reported collisions ended the five years roughly where it began, while the serious end of the count rose.
Fatal collisions are rare and do not trend: two in 2021, two in 2022, none at all in 2023, three in 2024 and one in 2025.
On the borough’s own stretch of the M4 the file records 65 collisions in those five years, causing 81 casualties. One was fatal, in January 2024. Nine were serious. That is about 13 a year on the busiest road in the borough.
Two caveats matter. STATS19 counts only collisions reported to the police in which somebody was injured, so damage-only crashes are missing entirely. And the most recent year is the newest published, which the department revises.
What it means for you
- If you drove the M4 between junctions 8/9 and 10 on the evening of Wednesday 9 September, check your dashcam before the footage is overwritten. Most units loop within days.
- Use the collision appeal portal rather than 101 if you have video. It is the route the investigating officer asked for.
- Quote 43260470931 on any report, so it reaches the Serious Collision Investigation Unit rather than a general log, or use Crimestoppers on 0800 555 111 if you want to stay anonymous.
- There is no ongoing closure. Planned work is a different matter: the M4 eastbound between junctions 8/9 and 7 shuts overnight on Monday 14 September, and our Windsor roadworks and travel page has the rest of the week.
Sources
- Thames Valley Police, Appeal for witnesses following fatal RTC, M4, published 14:31 on 10 September 2026. All detail about the collision, the vehicles, the death and the absence of arrests is taken from this statement and nothing else.
- Thames Valley Police, collision appeal portal entry for 09/09/26.
- Department for Transport, reported road casualty statistics, road safety data, collision records for the last five years. Our figures are the rows whose local authority is E06000040, the Royal Borough of Windsor and Maidenhead, counted by severity and by year.
No arrest has been made and no proceedings are active. We do not name people the police have not named, and we do not report court matters. If anything here is wrong, tell us and we will publish a dated correction.
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