The alignment under Swanston St between CBD North and CBD south stations to be built by “mined cavern” design

Melbourne’s Metro is scheduled to start operating in 2026, which happens to be an election year. But according to The Sunday Age on the weekend, it will be constructed in a way that speeds the project up at the expense of additional truck movements through the CBD.

The paper obviously thinks it’s on to a big story here; it not only ran a 1,000 word report in the news section accompanied by seven pics/charts, Metro Rail: Tunnel dig will see 438,000 trucks through CBD over four years, it also piled on a 500 word editorial, The curious haste of the Metro project:

We have learnt Melbourne’s CBD will see more than 430,000 extra trucks rumble through it as part of the Metro Tunnel project. Like the omission of the South Yarra upgrade, it would seem the reason for those trucks is to meet a tight deadline, rather than the needs of the city.

The timeline set by the Andrews Government is for work to begin by 2018, tunnelling and truck disruption to end by 2022, and the project to be operational in 2026. In the four-year cycle of Victorian politics, all of those years are election years. Let us hope the government is not prioritising an agenda of positive news in an election year over the needs of a city.

According to the paper, the problem is the section of the tunnel under Swanston St between the two new stations, CBD North and CBD South, will use a “mined cavern” design that requires excavated soil to be removed by trucks, whereas the sort of Tunnel Boring Machine (TBM) used for the rest of the tunnel removes the soil behind it as it advances.

TBMs are impressive but they’re slower than a snail: using the “mined cavern” design means the CBD section can be built without waiting for a TBM to arrive at the CBD from the Flemington and South Yarra ends of the tunnel.

The idea that a government might cynically manipulate key project parameters, like cost and timing, to improve its political welfare is eminently believable; indeed, its par for the course.

But it’s odd to see a government being taken to task for wanting to get a project finished sooner rather than later. While it doubtless suits the Government politically, building Metro quickly is also good for travellers. The rail system in Melbourne is groaning at peak hour from demand, as The Age often tell its readers. Metro will increase passenger capacity and, importantly, improve system-wide reliability.

Getting Metro up and running as soon as possible means Melburnians will be better off; they’ll get to enjoy the benefits of the project earlier. That’s why it’s being built in the first place. From what I can see, everyone with an interest in the city’s public transport system wants Metro to open as planned by no later than 2026. Sooner would be terrific – many think it’s taking too long – but later would be a poor outcome.

The section of Swanston St that’s at issue here isn’t huge. It’s about 700 metres from the bottom end of CBD North Station at La Trobe St to the top end of CBD South Station at Collins St. The total length of the new line is 9 kilometres, including tunnels and stations (each station is a deep, 250 metre long, excavated cavern).

Even if this section were constructed by TBM, the soil would still have to be carried away by truck from the ends of the tunnel at inner city Flemington and Sth Yarra.

Disruption is part and parcel of all big projects, especially where infrastructure is being retrofitted in established areas. Governments and designers are aware of the impact on business and residents of big projects like the current program of level crossing removals and motorway widenings.

The former state Government even argued its version of Metro was shaped by the need to avoid disruption in Swanston St; it used a route down the western end of the CBD. It had other advantages too, but it wouldn’t have delivered the same benefits as Metro e.g. new stations interchanging with Flinders St and Melbourne Central Stations; relief for trams on Swanston St.

The 438,000 truck movements cited by The Sunday Age is over four years and translates to an additional truck every five minutes through the CBD. The argument is always that the pain is short-term and small relative to the long-term benefit stream the project creates.

The Sunday Age also suggests the Andrews Government omitted a new Sth Yarra interchange station from Melbourne Metro because it would delay completion of the project until after the 2026 election. It’s not obvious why a sixth station would delay the project, but there are in any event other sound reasons to omit a new station at Sth Yarra at this time; it has a poor benefit-cost ratio, it’s costly, it requires a large number of properties to be demolished, there are other ways for Sth Yarra users to interchange with Metro, and it’s not essential to the purpose of Metro (see Would building this new rail station be a sensible idea?).