Emergency services have been sent to Long Furlong after a collision left a driver with serious injuries, police say.
Officers were called to a report of a collision between two vehicles on the A280 Long Furlong near Clapham at 3.50pm today.
The road is closed in both directions from the Findon Valley roundabout.
One driver has been taken to the Royal Sussex County Hospital, Brighton, with serious injuries.
The road has been reopened.