According to traffic reports, a water main has burst on A2270 Eastbourne Road in Willingdon.
Temporary traffic lights are in place, causing long delays between Polegate and Eastbourne.
Delays are said to be increasing on A2270 Eastbourne Road sothbound between A27 Lewes Road and Downs Road. The average speed has been reported as ten mph.
This follows a serious crash on the A23 in Crawley, in the early hours of the morning.
West Sussex Fire and Rescue Service said, just after 4.30am, that it was on scene at a road traffic collision on the A23 between Martyrs Avenue and the Tushmore roundabout.
Sussex Police said the road would remain closed 'for some time'. Read more here
Rail delays have also been reported in West Sussex this morning.
Southern Rail said it was informed of a fault on a train between Havant and Chichester.
Trains are able to run in the other direction, from Chichester towards Havant and Portsmouth direction but the line towards Chichester is blocked.
Rail replacement buses have been requested.
A Southern spokesperson said: "Engineers are on site and assisting to attach the rescue unit to the broken down train.
"Services are unable to run between Havant & Chichester in both directions.
"If you're travelling on this route, please check before you travel and leave an extra 30 minutes."
Meanwhile, slow road traffic has been reported in Chichester, on A27 eastbound before A259 Cathedral Way (Fishbourne Roundabout).
There is also reportedly slow eastbound traffic on the A27 near Worthing.