The incident happened at 4.39pm on Saturday 10 April 2021 on the A20 Ashford Road between the junctions with Downlands and Dickley Lane.
A blue Audi A3 was driving towards Maidstone when it was involved in a collision with a blue Volvo articulated lorry travelling in the opposite direction.
The Audi driver, a woman in her 40s, was taken to a London hospital where she remains in a serious but stable condition.
Anyone who saw the incident who has not yet spoken to officers, or who has dashcam footage which may assist the investigation, is urged to call the Serious Collision Investigation Unit on 01622 798538, quoting reference DB/FM/032/21.
You can also make contact with investigators by email firstname.lastname@example.org.