More than six miles of traffic has built up on the A1 close to Pontefract this afternoon.
It is understood that an accident on the northbound A1 close to Wentbridge Viaduct, near Darrington, has closed the road.
Three miles of traffic has built up on the southbound carriageway, with a further six miles of congestion northbound.
Delays of up to an hour are expected.
In a tweet, Highways England said they were responding to a multi-vehicle accident which had blocked the carriageway.
Traffic officers are on scene.
Two lanes have also been closed at junction 49 (Dishforth), in North Yorkshire, after a multi vehicle collision.