A crack on a viaduct carrying the M25 in Hertfordshire has closed a busy section of the orbital road.
Highways England shut the motorway to anti-clockwise traffic from junction 21A to junction 20 - apart from one lane of traffic that is being allowed to join from the M1 southbound at junction 21 - at 1.30am this morning.
The Connect Plus consortium is overseeing repairs to Gade Valley Viaduct, which carries the M25 over a railway line, a road and a river, towards junction 20 near Kings Langley.
Highways England said the road was likely to reopen this afternoon.
A Highways England spokesperson said: “Safety is Highways England’s top priority. During a routine inspection yesterday a minor crack was discovered on the Gade Valley Viaduct near to the M25 junction 20.
“The closures are in place to allow repairs to be carried out as quickly as possible to stop the crack from growing and maintain safe journeys. We would like to thank drivers in advance for their patience and reassure them that we will be working as hard as we can to reopen the M25 as soon as safely possible.”
Works to replace two expansion joints on the Gade Valley Viaduct, which had reached the end of their serviceable life, took place from March 2015 until the start of this year.