Will an airport rail link reduce GHGs?

Given the evident public interest in the idea of a rail link from the  CBD to the airport, I thought I’d look more closely at some of the key rationales for this project, starting with the claim that it would reduce greenhouse gas emissions.

Energy use and emissions (PTUA)

I’ve looked at this issue and, on my admittedly simple calculations, I conclude that the value of greenhouse gas (GHG) savings from a rail line is likely to be minor compared to the probable cost. There are far cheaper ways to offset equivalent emissions than building a rail line.

I looked at this by making the following simplifying assumptions.

First, I assume that a new rail line captures 20% of airport passenger traffic or five million of the current 25 million annual passenger movements at Melbourne Airport. This is double the share captured at either Sydney or Brisbane (around 10%), and almost three times the 7% estimated in feasibility studies.

Second, I assume that all of the current two million passengers using Skybus transfer to the new train (i.e. Skybus ceases to operate) and three million passengers transfer from cars, including taxis.

Third, I assume an average distance of 22 km from the CBD to the airport for bus and train. I assume that the combined average distance travelled to the airport by the cars and taxis that are replaced by train is 35 km. Read the rest of this entry »