The M8 eastbound was closed after a trailer full of turf overturned strewing debris across the road.
The crash near Junction 27, Arkleston Interchange, shut the slip road off while emergency services attended.
Traffic has been queuing since 1.15pm with the jam reaching back for almost five miles past Glasgow Airport to Junction 30, Craigton Interchange.
Traffic Scotland said police and the Trunk Road Incident Support Service were in attendance with delays of an hour at 2.20pm.
Shortly after 2pm, a spokesperson said: “Road traffic collision on the M8 eastbound at Junction 27. Lanes one and two of three are closed as is the off slip due to an overturned trailer and debris on the carriageway. Traffic queuing back to Junction 30.”
A Police Scotland spokesperson said: “Around 1.10pm on Wednesday, July 21, we received a report of an overturned trailer on the M8 eastbound near junction 27.
“The road is currently obstructed and uplift of the trailer is being arranged.”