Obsolete traffic lights at the junction of Teville Road and Oxford Road have been replaced with temporary signals in preparation for replacement work to begin on Monday (August 3).
But a fault with the lights has left traffic queuing at the junction near Worthing Railway Station.
Earlier this week, West Sussex County Council announced its intention to replace the old lights with 'more reliable and energy-efficient' equipment.
A West Sussex Highways spokesman said: “The new equipment will use LED technology, improving the signals’ reliability, reducing maintenance and saving energy. They will also be more reactive to traffic movements.”
While the works are ongoing, the temporary traffic lights will not react as quickly as permanent signals and queues are likely on approaches to the crossroads, said the spokesman, and advised motorists to use alternative routes during peak periods.
The spokesman added: “We apologise for any inconvenience caused during the work but please bear in mind this project will lead to long-term improvements.
“We will do all we can to try to minimise disruption, such as manually controlling of the temporary signals during busy periods.”
Subject to factors such as severe weather, the project is scheduled to take up to eight weeks to complete.
The scheme is estimated to cost around £190,000.