Emergency crews freed a woman trapped in her car after it overturned near a roundabout.
The driver, in her early forties, has been taken to a London hospital with injuries described as "serious, but not life-threatening".
Police were called to Brewers Road, Cobham, at 4.21am, and the A2 London-bound slip road at the Gravesend East junction remains closed.
Fire fighters and paramedics were also at the scene.
A spokesman for Kent Fire and Rescue Service (KFRS) said: "KFRS was called to a crash involving a vehicle on its side.
"Three fire engines attended and crews worked to release one casualty by removing the windscreen.
"She was handed into the care of paramedics."
It happened just minutes before a similar incident at Old Road East, Gravesend, in which another car overturned.
Police were called at 5.09am, but no one was found in the vehicle.
Kent Police spokesman, Sally Smith, said: "Inquiries are ongoing to locate the driver to ensure they are safe and well."