Is Sydney’s new light rail line about saving the planet?

Sydney's new CBD and South East light rail line shows that emission reductions are usually only a small component of the benefits of multi-billion dollar public transport investments

Benefits of the CBD and Eastern Suburbs Light Rail extension (source: TFNSW, CSELR Business Plan Summary)

There's a common view that a key warrant for major public transport investments is the positive impact they'll have on the rate of global warming.

In most cases though, the environment isn't the main winner from big transport projects; even ones aimed at public transport users.

Consider the NSW government's $2.1 Billion CBD and South East Light Rail extension that will run from Circular Quay to Randwick and Kingsford. TheBusiness Plan Summary estimates the benefits from this investment will total $4 Billion, giving a Benefit Cost Ratio of 1.9. 

As the exhibit shows, it's estimated more than half of all benefits from the project will accrue to existing and future public transport users in the form of faster, more comfortable and more reliable travel than provided by the buses they would otherwise use.

There are a number of other winners too. The new line is expected to generate operational savings and additional revenue for the public transport operator (i.e. the NSW government), as well as benefitting motorists through "decongestion" of roads.

Pedestrians will benefit from improved amenity, principally in George St; and it's assumed there'll be wider economic benefits (WEBs) from more urban renewal opportunities.

However the environmental and social benefits – which comprise reductions in emissions and air and noise pollution, as well as improvements in health – total $0.31 Billion combined. That's just 8% of the expected $4.0 Billion benefits.

Unfortunately, the summary Business Plan doesn't separate environmental benefits from health benefits. However it estimates the light rail service will reduce greenhouse gas emissions by an average 23,300 tonnes per year over 30 years by replacing bus and (some) car trips. But even at a price of $100 per tonne, that's only worth around two million dollars a year.

The decidedly modest payoff in terms of reduced emissions shouldn't be a surprise. The light rail system will move many more travellers out of buses – another form of public transport – than out of cars.