Traction energy associated with operation of the HCMTs represents by far the largest source of GHG emissions (56 per cent) associated with the infrastructure lifecycle of the project due to the higher energy requirements of these trains compared with existing rolling stock.
Traction energy associated with operation of high capacity trains represents by far the largest source of GHG emissions associated with the 100 year infrastructure lifecycle of Melbourne Metro due to the higher energy requirements of these trains compared with existing rolling stock

I’ve remarked before that building costly new rail infrastructure in Australia’s big cities in most cases won’t generate much mode shift from cars to public transport (e.g. see Will simply building more public transport seriously suppress car use?). The warrant for new heavy and light rail lines isn’t about climate change; rather, it’s primarily to support large agglomerations of activity like the CBD and to provide non-motorists with mobility.

The newly released Environmental Effects Statement for the $11 Billion (nominal) Melbourne Metro rail tunnel illustrates this point. The project involves connecting the Cranbourne/Pakenham Line to the Sunbury Line by constructing twin nine-kilometre rail tunnels under the CBD and five new underground stations.

Melbourne Metro will generate an estimated 543,400 tonnes of greenhouse gas during construction, assuming best practice methods are adopted. Most emissions though will come when it commences operations in 2026.

High capacity seven-car trainsets will operate on the tunnel initially (expandable to ten cars) so it will use a lot of electricity. Compared to the “no Metro scenario”, the project is estimated to generate an additional 70,900 tonnes of greenhouse gas per year in 2026. The EES expects emissions to fall to 58,000 tonnes by 2046 due to a progressively higher proportion of the State’s electricity coming from clean sources. (1)

It would be possible to reduce operational emissions – to 47,600 tonnes at 2026 and 37,600 tonnes at 2046 – by adoption of best practice methods. These would incur a cost though e.g. purchasing more expensive green power.

These are big numbers but in the context of the State’s total net emissions – 123,900,000 tonnes in 2013 – they’re very small.  The EES says the operational emissions of the project would make “a negligible contribution to regional GHG emissions” i.e. in the order of 0.1%.

On the positive side, Melbourne Metro will generate mode shift i.e. some travellers will shift from private vehicles to trains to take advantage of the increased capacity provided by the project. The EES says it will remove an additional 286 million kilometres of car and truck travel from Melbourne’s roads in 2046. This translates to an estimated saving of 74,000 tonnes of GHGs in that year.

Thus after allowing for the increased operating emissions attributable to the tunnel on the one hand, and the reduction in private vehicle emissions on the other, the project will yield a net saving in operational emissions of 16,000 tonnes in 2046, or 36,400 tonnes if best practice operating methods were adopted.

That’s a clear benefit but there’s no getting away from the fact that they’re extremely small numbers. The justification for spending $11 Billion to build Melbourne Metro – and generating 543,000 tonnes of GHGs during construction – has almost nothing to do with reducing car travel.

Much bigger gains in lowering emissions could be made by vastly more cost-effective approaches e.g. increasing taxes on motor fuel, regulating vehicle size, replacing coal-fired power stations with clean energy sources to support electric vehicles.

The key rationale for Melbourne Metro – obviously enough – is transport. It’s to provide additional capacity in the rail system to support the continued growth of the CBD and to increase network reliability by enabling all passenger lines to operate independently from end to end. Seriously reducing emissions will require much more politically difficult actions than building the occasional popular new rail line.

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  1. For the purposes of this discussion I’ve ignored Scope 3 emissions (the EES says they increase 2026 operating emissions to 98,000 tonnes p.a., or 74,700 tonnes p.a. with best practice methods).
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