Sydney has the unenviable title of Australasia's most congested city after a report from a peak transport body revealed it features seven of the 10 slowest roads on both sides of the Tasman.

And in a sign of the mounting pressures of a booming population, average speeds of 72.5 kilometres an hour on Sydney's road network – which includes motorways such as the M7 and M2 – are even slower than New York.

The Austroads report shows Sydney is worse than Melbourne on most measures of congestion, including the extent to which motorists are delayed and need to allow for extra time to reach their destinations at peak periods.

And when compared with international peers in the United States, the average speed on the Sydney road network is slower than San Francisco, Boston and Philadelphia – which range from 79 to 86km/h – and only slightly faster than Seattle's.