The collision took place shortly after 2pm on Saturday on the northbound carriageway resulting in a lane closure.
Traffic Scotland confirmed at around 3.30pm that the lane had fully reopened but traffic remains very slow tailing back onto the M90 spur.
The nature of the incident is not yet known.
The accident comes after police closed the M8 in both directions this morning after reports of a distressed man.
A diversion was put in place on the B7066 between Whitburn and Kirk of Shotts and the motorway reopened at around 9am.
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