Transport Emissions - The True Picture

A new report aims to illustrate the true picture of the level of CO2 and other greenhouse gas emissions associated with different forms of passenger transport like aircraft, trains and automobiles. 

Rather than just assessing the impact of the direct use of them, the study – carried out by the University of California’s Arpad Horvath and Mikhail Chester – took into account all elements involved in constructing, running and maintaining 11 various transport types in operation in the US.  It also factored in the greenhouse gas emissions associated with the fuel from which they derived power.

Emissions from Trains, Cars, Aircraft

In this way, the two researchers put emissions from trains, cars, aircraft and other transports on an equal plateau.  They did this by working out the volume of passengers carried by each, and the distance it would travel while in service, while also covering related infrastructure like roads for cars and airports for passenger airliners. 

Unsurprisingly, the end results depicted a higher greenhouse gas emission output than from fuel combustion alone.  For trains, emissions increased twofold while, for cars, they were up over 30 per cent.  In the case of aircraft, which didn’t require a manufactured surface to operate on (as with cars and roads), the emissions increase was less dramatic, but was still as much as 20 per cent higher.

Transport Emissions Per Capita

The only instance of transport emissions per capita exceeding cars was that of buses running off-peak, which operated with limited number of passengers on board.  The researchers compared a typical one mile bus journey at the busiest and quietest times of the day and discovered that the emissions created off-peak were eight times over those during rush hour. 

Another discovery was to do with electric forms of transport, like electric cars and trains.  While the cars and trains themselves weren’t emitting directly into the atmosphere, the electricity powering them could be, if it was created from industrial fossil fuel incineration.  This was especially true in Boston, which has an electric train system in place, but which is also an industrial incineration hotspot.

Environmental Impact of Transport

Therefore, said the researchers, different approaches should be taken when considering the environmental impact of transport modes.  While, as a component of so-termed “Life-Cycle Emissions” for cars and aircraft, emissions generated by engines/exhausts dominated the scene, this was not the case for trains, where stations, tracks and other infrastructure elements made up the majority.  With this in mind, Chester urged any governments looking to make more use of rail to consider the wider picture – not just the carbon footprint of the trains themselves.