Drivers had their first taste yesterday of more than a year of traffic delays in the CBD caused by the Elizabeth Quay development.
Thousands of city workers returning from Christmas holidays were greeted by heavy early morning congestion on Mounts Bay Road.
The busy road was cut from three lanes to one between Mill and William streets for work on the waterfront development.
Traffic was at its worst in the morning, with peak-hour traffic backed up towards the freeway interchange and Narrows Bridge.
Another two lanes are closed between William and Barrack streets.
While traffic flow eased as the day wore on, long delays are expected during morning peak hour as the works continue over the next month.
The full impact of the project on traffic is not expected to be felt until November, when Riverside Drive will be closed and traffic rerouted around the Elizabeth Quay inlet.
State Government modelling estimates up to 10 minutes will be added to peak-hour travel times.
Congestion is expected to increase on Walcott Street, Charles Street, Manning Road and Mill Point Road as drivers attempt to avoid the area.
Up to 40,000 extra vehicles are expected to use the Graham Farmer Freeway with extra lanes planned for the Northbridge Tunnel to cater for them.
Main Roads has advised drivers to expect delays during the roadworks and to seek alternative routes.