A diesel spillage is causing long delays on the motorway and local roads.
The exit slip road at j20 for Kings Langley on the M25 anti-clockwise is closed and highways officers have also closed one lane on the main carriageway too.
Highways England says the road surface is not safe for drivers to use.
There are tailbacks of more than five miles on the M25 all the way back to j22 for London Colney and the disruption has had a knock-on effect on the A414 between the London Colney roundabout and the Park Street roundabout.
DELAYS: A414 #ParkStreet roundabout #StAlbans W/B. Delays occurring due to problems on J20 #M25 with a broken down vehicle causing long tailbacks, extra traffic along A414. pic.twitter.com/uAYE6S7LAS
— HCC Highways (@Herts_Highways) December 13, 2018
There are also delays on the A405 towards Watford between the M1 and St Albans Road.
Anyone looking to leave the M25 at j20 should be aware that the next get-off is j18 for Chorleywood. There are no delays past j20.
Motorists are advised to avoid the M25 between j22 and j20 if possible.
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