An A-road between Hitchin and Stevenage is partly blocked this evening after a crash and oil spill.
The AA report that westbound traffic is queuing for five miles behind the incidents on the A602 Parkway between Stevenage Road and the A505 Upper Tilehouse Street.
It is unclear if the crash and oil spill are related.
Congestion is building up to A1(M) junction eight, by Lister Hospital, and Hertfordshire County Council Highways department has described the delays as "extreme".
It has advised drivers to seek alternative routes.
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