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Cars & traffic

Nov 21, 2017

Is this underpass promise under-developed?

The promise by the Opposition in Victoria to grade-separate 55 congested intersections is likely to be politically appealing, but the case hasn't been made it's a sensible policy

Alan Davies — Editor of The Urbanist

Alan Davies

Editor of The Urbanist

Illustrative works at the intersection of Lower Heidelberg Rd and Banksia St. The existing option for vehicles in Heidelberg Rd to turn right is conveniently omitted from the grade-separated version. That would reduce scale and cost, but also make it less effective (source: Liberal Victoria)

The Leader of the Opposition in Victoria, Matthew Guy, announced yesterday a program to grade-separate 55 selected road intersections in the state if the Liberal Nationals win next year’s election. Mr Guy says the imaginatively titled Traffic Light Removal Project would favour underpass rather than overpass construction, cost up to $5.3 Billion, and be implemented over two terms (eight years).

The parallel with the popular $6.9 Billion program to grade-separate 50 rail level crossings over eight years the Government took to the 2014 election is obvious. Mr Guy might not be original but he’s politically smart; he’s promising a solution to traffic congestion that’s targeted at multiple electorates.

The promise has inevitably invited the criticism that it will encourage car use. Yes, if it really does reduce congestion that’s inevitable. But it’s jejeune to expect there’ll be no investment in roads in a growing city where 90% of households have at least one car, where 89% of motorised trips are made by car, and where driverless vehicles are looming larger on the horizon. Moreover, the 35 intersections nominated so far are all in the suburbs.

Critics say the money should instead be spent on improving public transport, but that would do little to reduce congestion. Consider that the Melbourne Metro tunnel will provide seats for an additional 39,000 passengers in peak periods and is costing $11 Billion; that’s a modest return in terms of changing mode share given there are around 3.5 million private vehicle trips per day in Melbourne in peak periods.

A more pertinent criticism is that the proposed works wouldn’t reduce congestion by much. Rather, they’d simply shift it to the next intersection. This is why road authorities tend to favour motorways; the BCR is often only acceptable if all or most intersections can be removed. If the program wouldn’t reduce congestion significantly, then worries about encouraging car use are beside the point.

Tbere’d be benefits from Mr Guy’s program but they wouldn’t come in the form of a reduction in congestion. They’d mostly come from increasing capacity in peak periods, albeit at congested speeds, and from faster speeds in the off-peak. Trucks and buses could be key beneficiaries, especially if the opportunity is taken to give them priority roadspace. However whether the benefits would exceed the costs, or even whether the estimated costs are plausible, is entirely unknown.

If Mr Guy really wants to do something to reduce traffic congestion he will need to promise a comprehensive road pricing scheme for Melbourne, as per Infrastructure Victoria’s headline recommendation in its 30-year infrastructure strategy. The agency also notes:

The introduction of a pricing scheme to influence how the transport system is used and the widespread use of driverless cars could dwarf the impact of building any new major road or rail line.

That’d be political suicide of course; it’s entirely academic in the context of the 2018 state election but it’s the only way to effectively tackle congestion.

A more relevant concern is the absence of any rationale for the selection of the initial 35 intersections. Infrastructure Victoria recommended a program of upgrades to arterial roads in the outer metropolitan area, whereas most of the nominated sites are within the ring road and Eastlink. We can be very confident their political value hasn’t been ignored.

Another source of unease is the scale and cost of the promised works. The engineering challenge involved is more daunting than the selected examples in the Opposition’s supporting document indicate. Unless they’re nobbled like the one in the exhibit, the impact on adjacent land uses and amenity could be very significant.

Unlike rail lines, roads provide access to properties and room for pedestrians, street activities, and car parking. Most will also need to maintain provision for turning traffic; right-turning vehicles are a particular challenge with grade-separated intersections, something conveniently omitted from the example in the Opposition’s marketing video (see exhibit). Indeed, the implication of the video is that the intersection design could make travel times for many motorists longer!

That means the cost of the program could be a lot higher too. The supporting document issued by the Opposition has a section titled ‘Costings’ but there’s no explanation whatsoever of how the $5.3 Billion was calculated.

As always, the key questions are whether the benefits of the promised program would exceed the costs; and even if they would, whether there are other ways to spend such a large sum of money that would deliver a better outcome for citizens. Naturally the Opposition hasn’t done that calculation. I can see the political appeal, but the case hasn’t been made that this is a sensible policy.

Notwithstanding the establishment of Infrastructure Victoria, extravagant and unsupported promises sanctified by an election remain a key problem for good policy-making.

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2 thoughts on “Is this underpass promise under-developed?

  1. Damien Mugavin

    You say: the impact on adjacent land uses and amenity could be very significant. I would say not ‘could’ but would. Urban blight develops at grade separated intersections and adjacent to elevated roadways. Indeed, in many cities, grade separation is being removed.

  2. Roberto

    Left turn slip lanes make cycling dangerous. The Dutch seem to have figured out better intersection design, with a half height underpass and a half height overpass giving much better grades. But probably on ring roads not on roads they might want to reduce motor traffic on, not encourage easier access. Different thinking.