Cars collided and traffic jams stretched several miles after a diesel spill on a major road.
Isaacs Lane, between Burgess Hill and Haywards Heath, remained closed this morning.
Police said the spill happened at about 7pm yesterday and at one point a traffic tailback stretched all the way into Burgess Hill.
There were three minor collisions caused by the slippery surface but there were no reports of injuries.
Gritters were called in but police decided the road was still too dangerous to use.
A spokesman for West Sussex County Council highways department said they hoped to reopen the road by noon.
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