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Heavy traffic is expected due to a crash on a diversion route.
Traffic has been channelled through the B245 in Hildenborough since Friday last week after the A21 was closed for essential repairs.
The crash is reported to have happened on Tonbridge Road between Hilden Avenue and Hilden Park Road.
Kent Police are attending and drivers are advised to expect long delays.
A spokesman for Kent Police said: "Kent Police was called at 2.40pm regarding a collision involving a car and a van on Tonbridge Road, Hildenborough.
"Officers and paramedics attended the scene where a woman received medical attention before being taken to a local hospital."
A spokesman for South East Coast Ambulance Service said: "Ambulance crews attended the scene and assessed and treated a woman at the scene.
She was then taken to Tunbridge Wells Hospital for further treatment."
The A21 through Tonbridge is shut until 6am on Monday, February 24, for essential repairs to the Manor Farm subway and Medway viaduct.