Australia's toll road king, Transurban, warns congestion in Sydney will match the clogged streets of Mexico City within decades unless motorists are properly charged for their use of the road network.

The dire warning from Transurban chief executive Scott Charlton follows attempts in recent days by the federal Minister for Major Projects, Paul Fletcher, to kickstart debate about a national system of road pricing.

Mr Charlton said a shift to a user-pays model was the only way to ensure Australia's cities did not grind to a halt over the next two to three decades.

"Even factoring in committed projects such as WestConnex and NorthConnex, and all the currently committed rail projects, by 2035 Sydney motorists could face congestion levels on par with Mexico City and spend 110 hours a year in traffic," he told a Committee for Economic Development of Australia luncheon on Tuesday.