Traffic was stopped on the M25 clockwise between J2 (Dartford) and J3 (Swanley) due to a serious collision on Friday afternoon, causing eight miles of tailbacks.
Traffic officers and emergency services were on scene, National Highways said, with 90-minute delays reported near the Kent passage.
It comes before the motorway - which is Britain’s busiest - will be closed in both directions between junctions 9 and 10 in Surrey from 9pm on Friday until 6am on Monday while concrete beams for a new bridge are installed.
The RAC has advised drivers on the route, especially those going on days out to attractions such as Chessington World of Adventures, that they should take extra food and drinks on their journey.
Diversion routes will take cars on a 19-mile journey on A roads, crossing from Surrey into London’s Ulez area, though National Highways has assured drivers “no enforcement action will be taken”.
But the highways authority said anyone who ignores official diversion signs in an attempt to find shorter alternative routes will be liable for the £12.50 daily Ulez fee if their vehicle does not meet minimum emissions standards.
Train companies have warned of amended timetables due to the overtime ban being observed by Aslef drivers.
Southern, Thameslink & Great Northern are aong the services affected, with the Gatwick Express not operating at all.
Meanwhile, the Overground and District Tube lines were part suspended on Friday afternoon. Scroll down for the latest travel updates across London’s travel network.
