Part of the M4 through Berkshire won't re-open until tomorrow morning after a lorry crash, which killed its driver.
A number of major roads across the Thames Valley have been at a standstill all day, with drivers caught in miles of tailbacks.
The lorry, carrying engine parts, crashed into the central reservation between junction 12 for Theale and junction11 for Reading, just before 5am. The eastbound carriageway - has been closed all day, with drivers diverted through Wiltshire, North Hampshire and Oxfordshire.
Reading town centre remains gridlocked this evening - several hours after the accident. Mel Bloor has our report.
The M4 eastbound remains closed between junction 13 (Chieveley) and junction 11 (Reading) after a lorry overturned at 5am this morning.
The outside lane on the westbound side of the M4 in the area also remains closed. Highways England said the accident recovery of the vehicle could take a long time.
The carriageway will have to be resurfaced before it can be used by traffic again because a lot of oil has leaked onto the road.
The recovery team includes workers and contractors from Highways England and Thames Valley Police. Motorists are being advised to delay their journeys if they can.
Highways England provides live traffic information. A diversion is in place via the A34, A303 and M3. Drivers heading to London can also use the northbound A34 and M40 route.
The police confirmed that the lorry driver died in the incident, and his next of kin have been informed.
Restrictions on the M4 westbound near Reading have been lifted after an accident on the eastbound carriageway.
There is still queueing traffic on the M4 Westbound between J10 A329(M) Wokingham / Bracknell and J11 A33 / B3270 (Reading). The eastbound side remains closed. The emergency services are attending to an overturned car.
The M4 is closed in both directions after an accident. An overturned car means there is queueing traffic between J11 A33 / B3270 ( Reading ) and J10 A329(M) Wokingham / Bracknell.
The accident happened shortly after 2pm. The emergency services are investigating what happened. One air ambulance has left the scene and one remains at the site.
The A34 southbound is blocked due to accident before M4 J13 ( Chieveley / Newbury). All traffic is being held just before the M4.
One lane is closed due to a broken down lorry and recovery work on M4 Westbound between J13 A34 ( Chieveley / Newbury) and J14 A338 (Hungerford). It is in the roadworks area. A tanker has broken down in lane one of three, halfway between the junctions. No delays at present.
One lane closed and queueing traffic due to multi-vehicle accident on M4 Westbound between J10 A329(M) Wokingham / Bracknell and J11 A33 / B3270 ( Reading ). Lane three (of three) is blocked by around five cars.
Two lanes are closed and traffic is slow on the M4 Westbound between J12 A4 ( Theale ) and J13 A34 ( Chieveley / Newbury) after an accident involving a van towing a trailer. Lanes one and two (of three) are closed.
One lane is closed due to barrier repairs on the M4 London bound after J10 A329(M) Wokingham / Bracknell in Berkshire. Lane three closed, with all traffic passing in lanes one and two.