There are delays of up to 20 minutes on the A303 eastbound from Picket Twenty this morning.
The cause is a single-car collision in the outside lane.
A Silver Vauxhall Corsa has crashed into the central reservation so hard that his front wheels have crashed completely into the car.
The driver appears unhurt, although there is an ambulance on the scene.
Traffic is moving at around 5mph.
Emergency services are in attendance.
Drivers are advised to find an alternative route.