It is expected to cause major delays in the area
Bus firm Stagecoach has tweeted to say its services have been hit.
It said: "Due to a serious RTC on the A361 at Caen Hill in Devizes, Service 49 will be on diversion for the foreseeable future via Rowde to Devizes. One bus is stuck in traffic and is running approx. 30 mins late. All other buses are operating via the diversion."