At Bulli there is a roundabout that intersects the Princes Highway and provides an entry point to Memorial Drive, as well as Molloy Street.

Motorists travelling north along the highway often drive as though the roundabout is not there.

A Transport for NSW spokeswoman said these motorists now needed to indicate as the highway veers to the left and a left turn is indicated by the lane marking.

Failing to indicate a left turn at a roundabout attracts a $180 fine and two demerit points.

The failure to indicate could be a contributor to southbound congestion at the roundabout as motorists stop because they are unsure if oncoming drivers are heading straight to Molloy Street or continuing left along the highway.

Executive director of the NSW Centre for Road Safety Bernard Carlon said the road rules at roundabouts were one of the most misunderstood road rules.

“Vehicles intending to turn left must indicate left on approach and continue to use their left indicator to signal their intention to exit at the first exit,” Mr Carlon said.

“It is particularly important for drivers to slow or stop to give way to any vehicle already in the roundabout.”