All lanes are open again after traffic was held following a crash between two vehicles on a dual carriageway.
Motorists were at a standstill on the A414 westbound between the London Colney and the Park Street roundabouts for around half-an-hour.
Fire crews helped release a person from one of the vehicles involved and they were left in the care of the East of England Ambulance Service, Hertfordshire Fire & Rescue has confirmed.
The crash happened as you go over the hill onto the approach to the Park Street roundabout.
Emergency services were at the scene and prevented any drivers from getting past.
Queues remain on the A414 between the Shenley Lane slip-road and where the crash took place.
Drivers can avoid the delays by travelling through St Albans or on the M25 between j22 and j21A. Traffic is clear on the motorway.
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