Drivers are being advised that there will be delays on the M4 during this evening's commute.
The westbound M4 is closed between junction 10 and junction 8/9.
The westbound carriageway remains closed after a lorry overturned just before 1pm.
One lane remains closed on the eastbound carriageway but additional lane closures may be required later to repair the barrier.
A signed diversion is in place following the hollow square symbol via the A329(M), A4, A3290 and A404(M).
Highways England said that it is working with the emergency services to reopen the road as soon as it is safe to do so.
Once Thames Valley Police has completed an investigation, extensive repairs will need to be carried out to the road before it can be safely reopened.
Initial inspections have identified that 300 metres of the central reservation and a light column has been damaged with possible damage to the road surface.
Highways England advised drivers to plan their journeys and to allow extra time as the closures are likely to continue through the evening peak period.