Sussex Police say that in the last 24 hours they have attended more than 300 collisions across the county.
Chief Inspector Phil Nicholas said: "The conditions meant there was a significant demand on our resources last night and we were stretched to capacity.
"Today is going to be about helping recover vehicles as many people fell asleep in their cars or abandoned them so even when the roads did become clearer they were still blocked by many vehicles.
"We will be assisting the Highways and other partner agencies to recover these vehicles. Although the conditions have inproved slightly, we are asking people to not make any journeys unless they are essential."
The A29 at Bury is still closed this morning.
The A23 is open and passable.
More top news
It's looking warm! Holly has the details.
Abby King has seen life-changing results after undergoing weight loss surgery in 2016. Her surgeon says many more people could benefit.
Progress has been made in talks under the chairmanship of the conciliation service Acas.