Police were called to the collision on the dual carriageway near Pyecombe at about 7.45am.
Officers said a BMW crashed into the barriers on the inside lane of the northbound carriageway.
Debris was scattered into the road, blocking the lane.
A police spokesman said a passerby stopped to help the driver and clear the road. No injuries were reported and both were on their way within a few minutes.
Commuters say they are experiencing half hour long delays due to the incident. Tailbacks are being reported as far as Brighton.
Don’t miss out on all the latest breaking news where you live.
Here are four ways you can be sure you’ll be amongst the first to know what’s going on.
1) Make our website your homepage
2) Like our Facebook page
3) Follow us on Twitter
4) Register with us by clicking on ‘sign in’ (top right corner). You can then receive our daily newsletter AND add your point of view to stories that you read here.
And do share with your family and friends - so they don’t miss out!
Always the first with your local news.
Be part of it.