Queues are building on the A602 between Hitchin and Stevenage following a collision near the roundabout for the A1(M) Junction 8.
Herts County Council Highways has advised drivers to allow extra time when travelling in the area.
The Comet is awaiting further information from emergency services, but there are also reports of very slow traffic on the A602 Parkway affecting travel times into Hitchin.
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