Exceptional Events on the M4

Most of what happens on the M4 is everyday traffic news: lane closures, roadworks and the odd breakdown. Now and then something much bigger happens, and it affects thousands of journeys for a day or more. This page records those exceptional events on the M4, what happened, when, and how drivers were diverted, so you can plan around them and look back at them afterwards.

Within less than a fortnight, the M4 between Maidenhead and Reading has two full closures in both directions: one without warning after a serious collision, and one planned for a whole weekend so that high-voltage power lines can be replaced.

Latest M4 traffic news

For everything currently reported on the M4, see our latest M4 traffic news and M4 roadworks.

Friday 18 to Monday 21 September 2026: M4 closed between J10 and J11

The M4 is closed in both directions between Junction 10 (Winnersh) and Junction 11 (Reading) from 9pm on Friday 18 September until 6am on Monday 21 September 2026, a closure of about 57 hours.

Scottish and Southern Electricity Networks are replacing a tower and the high-voltage wires that cross the motorway there, after the overhead electricity network was badly damaged earlier this year. You can read SSEN’s own announcement about the M4 closure (it opens in a new tab).

Drivers are being diverted via the A329(M) and the B3270. Junction 10 is where the A329(M) meets the M4 for Wokingham and Bracknell, and Junction 11 is the A33 for central Reading and Basingstoke. If you normally use the M4 through Reading at the weekend, allow extra time, or check whether your journey can avoid this stretch altogether.

Wednesday 9 to Thursday 10 September 2026: M4 closed between J8/9 and J10 after a collision

At around 9.20pm on Wednesday 9 September 2026, a serious collision closed the M4 in both directions between Junction 8/9 (Maidenhead) and Junction 10 (Winnersh). A police investigation kept the road shut overnight and through the Thursday morning rush hour.

The eastbound carriageway reopened by about 2.25pm on Thursday 10 September, around 17 hours after it closed. The westbound carriageway stayed closed while it was cleared, and both directions were open again by about 4pm, around 19 hours after the collision.

Westbound traffic was diverted off the M4 at Junction 8/9 onto the A404(M) to Junction 9B, then along the A4 towards Reading, the A3290 and the A329(M), rejoining the M4 at Junction 10. Eastbound traffic followed the same route in reverse.

Two closures on the same stretch of the M4

	9–10 September	18–21 September
Junctions	J8/9 (Maidenhead) to J10 (Winnersh)	J10 (Winnersh) to J11 (Reading)
Cause	Unplanned: serious collision	Planned: power line replacement
Closed	About 9.20pm Wed 9 Sept	9pm Fri 18 Sept
Reopened	Eastbound about 2.25pm, both directions about 4pm, Thu 10 Sept	6am Mon 21 Sept
Length	About 17 to 19 hours	About 57 hours
Diversion	A404(M), A4, A3290 and A329(M)	A329(M) and B3270

Both closures sit either side of Junction 10, where the A329(M) meets the M4, which is why that road carries the diversion both times. Between them they add up to more than three days in which part of the M4 around Reading had no through traffic.

The junction pages for these closures

For traffic figures and the full story of each closure, see M4 Junction 8/9 to 10 and M4 Junction 10 to 11, or how busy the M4 junctions are.

Why we keep this page

Live traffic news tells you what is happening now. Big events are different: people plan around them in advance, and talk about them for days afterwards. Keeping a dated record in one place means you can see what is coming, and what has already happened, without searching through old news. We will add to this page when the next exceptional event affects the M4.

Where to check the M4 now

See the latest M4 traffic news for everything currently reported in both directions, M4 roadworks for current and planned work, M4 accidents and incidents, and the messages on the gantries at M4 overhead signs. Every junction is on our map of the M4 motorway junctions.

Weekend closure details from Scottish and Southern Electricity Networks, Wokingham Borough Council and National Highways. Collision closure times and diversion from National Highways travel alerts on 9 and 10 September 2026; reopening times are approximate.