The country's chief infrastructure adviser has urged the NSW and Turnbull governments to create a 300-kilometre Sydney bicycle path network, prioritise parts of Parramatta and Victoria roads for public transport and transform Newcastle and Wollongong into true satellite cities through high-speed rail.

Infrastructure Australia says such projects are vital to cope with a national population increase of 11.8 million in the next three decades - or risk losing $15 billion through congestion by 2031.

"If you can imagine adding two more cities the size of Melbourne or Sydney to Australia by 2047, you'll appreciate the enormity of the challenge," said Infrastructure Australia chairwoman Julieanne Alroe.

An artists impression of Green Square. Credit:Stewart Hollenstein

The infrastructure auditor has designated Western Sydney as the country's highest priority area, with four of the nation's top six projects of "national significance" located in the booming corridor.