There is slow traffic on the A27 both ways before the Toby Carvery in Worthing, the AA said.
Slow traffic is being reported on the A27 Eastbound before the A277 Brighton Road (Ashcombe Roundabout).
There is queueing traffic on A27 Polegate By Pass Westbound before A22 Polegate Road (Cop Hall Roundabout).
Traffic is also queueing on the A259 Little Common Road both ways at B2098 Sutherland Avenue in the construction area. There are temporary traffic lights around the electricity works until June 11.
He added: “Trains that usually run between London Bridge and Uckfield will now run between London Bridge and Crowborough.
“If you have not yet set off to the station, please travel later on today if you can.
“Rail replacement buses will run between Uckfield and Crowborough whilst this signalling fault is investigated further.”
Trains are able to run beyond Crowborough, Southern said.
The spokesman added: “If you wish you can use Lewes or Haywards Heath as an alternative station.
“Your ticket will be accepted on any train towards London (both Southern and Thameslink).
“You can also use Tunbridge Wells station with @SE_Railway services.
“You may be required to make use of an alternative route if you are travelling to / from Uckfield or Buxted today.”