Roadworks along the A259 in Worthing have been causing disruption as motorists queue along the seafront.
Congestion has stretched in both directions from the junction between Brighton Road and Ham Road, with some rush hour commuters experiencing delays of up to 25 minutes.
Tailbacks have stretched east past Brooklands Park and into Lancing, as well as west towards Worthing town centre.
The temporary traffic lights are part of repairs to the gas network being carried out by gas company SGN.
According to West Sussex County Council, the works are expected to last until Thursday, February 20.