“You may only enter a yellow box junction when your exit is clear and there is enough space on the other side of the junction for your vehicle to clear the box completely without stopping,” Main Roads congestion program director James Dobinson said.
“Drivers who are turning right can stop in a junction if their turn is prevented by oncoming traffic until it is safe for the turn to be completed,” Mr Dobinson said.
The yellow box junctions remind drivers to be aware, and not follow the car in front unless there is clear exit. Only one car should be in the intersection turning right while facing oncoming traffic.
The cross-hatching version of the boxes is being trialled at Jon Sanders Drive-Herdsman Parade, Glendalough, and Canning Highway-Kintail Road, Applecross. The lines are at Queen Victoria Street-Tydeman Road, North Fremantle, and a Mitchell Freeway southbound off-ramp, Leederville.
Mr Dobinson said the four intersections where chosen because of existing problems, such as trucks in North Fremantle.
He said whether other congested crossings, such as Eric Street-Stirling Highway in Cottesloe, got the warning lines would depend on the outcome of the six-month trial and guidelines being developed for selecting future sites.