A major report into the future of the Kwinana Freeway is under way amid fears more than 11km of it could be under water within 17 years because of rising sea levels.
The study by Main Roads and the City of South Perth was launched after the freeway was one of nine roads identified as most in need of protection from sea levels rising because of climate change.
A November 2011 report by Main Roads found a 300mm rise in sea levels was possible by 2031 and would put 121km of WA highways and State roads at risk.
"Whilst this represents only a very small proportion of our overall network, the roads in question are primary links to ports, significant towns and tourist destinations," it found.
After taking into account factors including traffic volumes, use by heavy vehicles, age of the routes and their strategic importance, 13 stretches of nine roads covering 50km were identified as warranting "early, more detailed, evaluation".
In Perth, these included 4.2km and 6.9km sections of the Kwinana Freeway between the Narrows and Mt Henry bridges as well as 270m of Mounts Bay Road and 100m of Hay Street near the Causeway.
Also on the priority list were two sections each of the Great Northern Highway and Broome Highway in the Pilbara and Kimberley, and two stretches of Pinjarra Road in the South West.
In answers to questions in the Legislative Council last week, Transport parliamentary secretary Jim Chown revealed Kwinana Freeway had been chosen for a pilot study to identify remedial or intervention treatments. A report was due mid-year.
Asked what work was being done on other priority sites, Mr Chown said the 2011 report was used by Main Roads "on a case by case basis when assessing the need to upgrade or improve road infrastructure close to the coast".
Shadow transport minister Ken Travers said it was appropriate Kwinana Freeway was looked at first but it was a concern closer assessment of other priority roads did not seem to have been done.
A City of South Perth spokeswoman said the report would consider the potential impact of climate change on the foreshore reserve, paths and the freeway and "discusspotential solutions".