The closure of the A4 Portway has been extended to cover a two-mile stretch of the busy road linking Avonmouth and Bristol.
A serious collision involving a lorry and a motorbike at around 5.53am closed the road in both directions near Sea Mills, initially from the A4162 Sylvan Way to Roman Way, but then further south to the A4176 Bridge Valley Road at Clifton Downs.
Traffic had been trapped in the closure - including buses - and congestion is widespread in the area.
Read more: Live updates as serious crash closes A4 Portway
The latest traffic information from Inrix, which provides real time information, said there is congestion to Abbots Leigh, Ashton, Clifton Down and all surrounding routes through Bristol as traffic diverts.
The collision happened on the southside of the road and people have been urged to avoid the area by emergency services.
As well as the road being closed to traffic, pedestrians were also told there would be no access as emergency services worked at the scene.
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