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The M20 was closed between two junctions after a lorry crashed.
The motorway was shut between Junction 4 and Junction 5 at around 6pm and motorists were told join the A228.
Police, the fire service and paramedics were at the scene of the incident between the junctions for West Malling and Aylesford.
Lane four of four remained closed at 9.20pm for repair work but the other three lanes had reopened to traffic.
A National Highways spokesman said: "Road users are advised to follow the hollow circle diversion symbol on road signs.
"Exit the M20 at J4 then take the A228 (northbound) and follow until the M2 J2. Join the M2 coastbound and remain on the M2 until J5.
"Exit the M2 and join the A249 (southbound) at Stockbury. Remain on the A249 until the junction with the M20 and re-join at J7.
"Delays are likely on approach to the closure and diversion routes."
A police spokesman added: "Kent Police was called to a single-vehicle collision involving a lorry between Junction 4 and Junction 5 of the M20 shortly after 6pm.
"Emergency services are currently at the scene and M20 is closed coastbound between Junctions 4 and 5."
One witness added: "A National Highways truck is now joining the traffic that has been allowed back onto the motorway."