The A58 Whitehall Road in Wyke was shut this morning after an ambulance overturned.
The emergency vehicle and a Subaru collided at 5.50am.
No one is thought to be seriously injured.
Traffic is very slow this morning in both directions between Hellfire Crossroads and Chain Bar.
There is also congestion on the B6379 Westfield Lane between A58 Whitehall Road and Tabbs Lane.