According to traffic reports, A27 Shoreham-Bypass is partially blocked eastbound after an accident between A2025 Grinstead Lane (Sompting Roundabout) and A283 Steyning Road (Steyning turn off).
'Severe delays' are said to be increasing in the area, with an average speed of ten mph.
Another accident has been reported near Haywards Heath.
There are reports of queuing traffic on A272 Lewes Road both ways near Chailey Heritage School after the crash, involving a car and a van.
The incident is said to be mainly affecting traffic between Newick and Haywards Heath.
Whist there have been no reports of an emergency incident in the area, 'severe delays' are said to be increasing on A24 Worthing Road southbound, between Mill Straight and Kippens Lane. The average speed is five mph.
Slow traffic has also been reported on A27 Chichester By-Pass eastbound before A259 (Bognor Bridge Roundabout and before A259 Cathedral Way (Fishbourne Roundabout).
There is also slow moving traffic on A259 Crookthorn Lane eastbound before Church Lane, near Climping.
In East Sussex, animals have been seen on the A21 near Robertsbridge. The incident has since been cleared.
There are delays on A259 Marine Drive westbound in Rottingdean and on A27 westbound towards the A22 (Golden Jubilee Roundabout).