Quicker traffic light changes can reduce congestion, according to an analysis of intersections on Tonkin Highway and Orrong Road.
The finding contradicts the long-held view of Main Roads engineers and many Perth motorists that longer green-light periods aid traffic flow.
The analysis, by Aurecon Consulting, found that reducing the traffic light cycle at the Tonkin Highway-Kelvin Street intersection from 250 to 190 seconds had cut vehicle delays.
A further cut to 145 seconds created more improvement.
"It is known in Perth that the public express that they like to have longer green times rather than short phases," the analysis report released this week says.
"But shorter phases mean that, on average, people will experience less delay." The report recommended that shorter cycle times be introduced and tested at other sites.
It said no "ideal cycle time" existed because it depended on the location and the traffic conditions throughout the day.
RAC spokesman Will Golsby said network management systems were a key part of dealing with increasing congestion.
Meanwhile, changes to traffic signals at inner-city intersections are still causing confusion for motorists and pedestrians.
Instead of having an exclusive pedestrian crossing phase, signals at the corners of Wellington-Barrack streets, Wellington-William streets, St Georges Terrace-Barrack Street and St Georges Terrace-William Street have been modified to allow pedestrians to cross at the same time as parallel traffic.
This can pose problems when a vehicle wants to turn left.
Yesterday, _The West Australian _ saw several instances where pedestrians were surprised to see vehicles trying to move between them. In one incident, a driver was visibly angry that pedestrians were blocking his way.
But a Main Roads spokes- woman said the changes had reduced wait times for all road users and the City of Perth was keen to convert more inter- sections.
"Not all intersections in the metropolitan area can operate as parallel walks," she said.
"It depends on the number of lanes pedestrians need to negotiate in crossing a leg of the intersection and the number of turning lanes for vehicles."Shadow transport minister Ken Travers said the new system had not been properly implemented. "The introduction of new signalling should have included better signage at the intersections and a public education campaign reminding motorists that pedestrians have right of way," he said.