Transport Minister Andrew Constance has questioned whether NSW should be building "four and five-lane motorways today" at a time when his government is constructing or planning toll roads worth tens of billions of dollars.

In comments that the state opposition labelled "an extraordinary admission", Mr Constance (pictured) said "we should be asking ourselves the questions" in light of technology advances that "could completely change the thinking".

His comments come as the NSW government is talking up the $16.8 billion WestConnex as a game changer for western Sydney motorists and touting the proposed Beaches Link tunnel, at an estimated cost of at least $3 billion, as a "congestion buster" for the north shore.

During an ABC radio talkback discussion on the future of transport on Sunday morning, Mr Constance enthused about the advent of driverless vehicles. "If you think about this in terms of, well, what does this also mean for car ownership, we won't own cars into the future; we'll subscribe to the service," he said.