Traffic is building on the A1 near Pontefract after a number of vehicles were involved in a crash.
West Yorkshire Police said initial reports suggested that three vehicles had collided on the northbound carriageway at around 11.20am.
One of two lanes is currently closed between the A639 and the junction 40 of the A1M.
Highways England has warned drivers to expect delays of around 30 minutes.
The scene is expected to be cleared by 2pm, although traffic conditions are unlikely to return to normal until around 2.45pm.