Building new roads will not by itself reduce Sydney's chronic traffic congestion, says an influential business lobby which is calling for the wider use of road pricing across the city.
A system of road pricing - such as a congestion tax like London's, or other measures to introduce charges on roads currently driven for free - is needed alongside a shift to public transport to deal with the city's congestion, the Committee for Sydney says.
The committee's push comes amid heightened official interest in changing the mix of tolls that currently apply to Sydney motorists.
Federal Minister for Major Projects Paul Fletcher has flagged a national study into the issue, though that is unlikely to be commissioned this side of the federal election.
"One of the things we've seen in researching global cities is that while increasing capacity on roads improves the number of people that can travel on those roads, you soon see congestion return to the same level it always was," said the head of strategy and advocacy at the Committee for Sydney, Eamon Waterford.
"That's not to say that new roads are never the right answer, but roads are not an effective congestion solution in many instances," said Mr Waterford.
In its report, the committee, which until recently was chaired by Lucy Turnbull, the wife of the Prime Minister and a former Sydney lord mayor, said the construction of a light rail line on George Street shows that in some instances traffic can be reduced when road capacity is removed.
"While the full impact of the light rail construction is still being investigated, it appears that traffic congestion did not worsen as commuters actually changed their behaviours and travelled by other modes, or outside the peak," the report says.
Introducing a different system of road pricing in Sydney is sure to be hugely contentious, and would not happen for years, if at all.
Sydney motorists already confront large numbers of toll roads - perhaps the greatest concentration in the world.
But a feature of the existing system in Sydney is that tolls are generally levied on new roads, which pushes traffic onto existing toll-free roads.
For example, government traffic forecasts for sections of the $16.8 billion WestConnex motorway, the biggest toll-road project in the country, demonstrate this effect dramatically.
The M5 East section of WestConnex is predicted to carry fewer cars when it opens in 2019 than the much-maligned Cross City Tunnel. That is because a toll of about $6 is expected to encourage drivers to use other routes such as Canterbury, Stoney Creek and Forest roads
The Committee for Sydney's latest report does not recommend any particular road pricing scheme to operate in Sydney.
But it canvasses options such as a "congestion tax" for motorists driving into inner areas of Sydney, of a sort used in London, Stockholm or Milan, or a more expansive system as used in Singapore.
The committee's push follows a statement by the NRMA and other motoring groups that they would support a system of replacing fuel taxes and other fees with a broader system of road pricing.
One of the potential problems with introducing more road pricing is the potential for the burden to fall on those living in areas without effective public transport.
But Mr Waterford said the current transport system was itself deeply inequitable. "People living at the outskirts of our cities pay an enormous amount in time because of congestion," he said.
