The M4 was closed westbound following a "serious incident" on Sunday August 20.
Police and air ambulance were called to the scene around 2.50pm.
The eastbound carriage way was shut to allow the air ambulance to land.
Highways England said around 4.45pm that all lanes had been reopened.
Thames Valley Police has been approached for comment.
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All lanes are now open
All lanes are now reopen following the earlier incident.
As soon as we get a statement from the police regarding the accident, we will update the website.
Traffic is slow from junction 6 as the car involved in the incident is recovered.
Highways England latest
Highways England has said normal traffic conditions are expected between 6pm and 6.15pm today.
One lane remains closed
Here is the latest update from Highways England:
Camera shows queues
This image from a camera at junction 9 shows the traffic queue building in the area. Police have asked motorists to avoid the area.
Highways England incident report
This is the latest incident report from Highways England:
Location The M4 westbound between junctions J7 and J8
Reason Accident involving a vehicle that has left the carriageway
Status Currently Active
Time To Clear The event is expected to clear between 16:30 and 16:45 on 20 August 2017
Return To Normal Normal traffic conditions are expected between 17:30 and 17:45 on 20 August 2017
Delay There are currently delays of 30 minutes against expected traffic
We have contacted Thames Valley Police for more information and will update you as soon as we can.
Tweet from Thames Valley Police
Thames Valley police have asked motorists to avoid the area.
Our traffic system is reporting stationary traffic in the area.
Traffic is being temporarily held on the M4 in both directions between junction 7 for Slough West and junction 8/9 for Maidenhead.
The incident has occurred on the westbound carriageway, and is reportedly a single vehicle incident.
Eastbound traffic has been held for arrival of air ambulance.
Highways England has confirmed there has been a serious incident with police on the scene and the air ambulance on route