Matthew Guy wants to reduce congestion at busy intersections. Credit:John Woudstra "This tends to be good for cars, but not pedestrians or cyclists. It adds to the capacity of roads to the detriment of other road users," Professor Stanley said. "Grade separation is only a short-term relief, it won't solve the problem of congestion." Removing traffic lights at intersections and roundabouts in some industrial and commercial areas along the Princes Highway might improve traffic flow, Mr Stanley said. But a statewide approach to easing congestion by digging trenches or creating overpasses in dense urban areas was "unheard of at this kind of scale in a city like Melbourne".

The Plan Melbourne strategy found that traffic flow on arterial roads was problematic, but it also called for "20-minute neighbourhoods", in which people would walk, cycle or use public transport to move around. Mr Guy on Monday revealed his multibillion-dollar plan to replace more than 50 of Melbourne's busiest road intersections with underpasses. The hit list of 35 intersections features some of Melbourne's widest and busiest roads, including the Nepean Highway, Springvale Road, Ferntree Gully Road, Fitzsimons Road, Princes Highway Sydney Road and Ballarat Road. The remaining 20 intersections to be removed would be chosen following community consultation.

"Census data shows that 74 per cent of Melburnians take a car to work every day," Mr Guy said. "That's why more of the same band-aid approach to addressing traffic congestion won't work." Mr Guy did not rule out building overpasses around Melbourne and Geelong, despite his party's firm opposition to building rail bridges in level crossing removals. Planning and transport experts have said the plan is reminiscent of a "1950s model of road design" that does nothing to boost the city's public transport system.

But the RACV has backed the proposal, arguing that it would reduce some of Melbourne's worst congestion, and also boost bus and tram services. "We support separation, we always have," said the RACV's general manager of policy, Bryce Prosser. "We need to get the most out of the existing network. Removing congested intersections increases the efficiency of the entire network, including making it easier for buses and trams." Mr Prosser said the RACV would conduct traffic modelling to ensure that the proposed modifications would not cause bottlenecks on surrounding roads and intersections. Director of RMIT's Centre for Urban Research Jago Dodson warned that Mr Guy's plan was reminiscent of a "1950s model of road design" that was not being mirrored in cities around the world.

"This is an anti-liveability proposal … it is something that is largely unique to Melbourne … many cities around the world are trying to reduce urban road space because we know that increasing car supply in the city diminishes liveability, yet Melbourne seems not to be learning that lesson." Public Transport Users Association's spokesman Daniel Bowen said the plan might deliver "short-term benefits" to traffic including buses and trams, "but more than likely, they will just get stuck at the next set of traffic lights." Mr Bowen said the removal of the unattractive Flinders Street overpass at King Street in 2005 was done to revitalise the western end of Flinders Street, while an overpass at St Kilda Junction has not alleviated traffic jams. Mr Bowen said he was concerned that building an under- or overpass at the Nepean Highway and Glen Huntly Road intersection would threaten the amenity of the area. "We would be potentially bringing spaghetti junctions into suburban areas across Melbourne," he said.

"I think people will see the impact of this on their neighbourhoods and are not likely to be favourable to it. You might not mind if you're driving throughout the area, but if you live and work there, the impact could be huge." Roads Minister Luke Donnellan questioned if the Opposition had done any work to analyse the impact removing the intersections would have on traffic. "Why rush people towards the next set of traffic lights without planning for the whole region?" he said. Replacing suburban intersections with diamond interchanges would inevitably require compulsory property acquisition, Mr Donnellan said.

