A Carpool Would Have Beaten That Bus

AUCKLAND ~ 19 February 2008 ~

A full bus might be less polluting than a single occupant car, but Paul Minett suggests that a carpool would be even better.

In the New Zealand Herald, Feb 18 2008, Mathew Dearnaley reported on a ‘competition’ between cars and buses on Auckland’s North Shore Busway. His conclusion: while cars were faster, bus travel was greener. Some additional calculations show that the answer is not so certain.

The comparison awarded ‘green honours’ to the bus because it carried 50 passengers at an average CO2 output per passenger of 0.406 kg. In comparison the car, a Hyundai Accent 1500cc with one occupant was found to have a CO2 output per passenger of 2.422 kg, or almost six times greater than the bus.

Had the calculation taken into account that the bus would have traveled empty to pick up the passengers, and then would travel empty back to get the next load, then the amount of CO2 output per passenger for the bus should have been at least double.

At the same time, had that car been a carpool with three occupants, the CO2 output per passenger would have been cut by two thirds.

Double the output for the bus, and divide by three the output for the car, and suddenly the answer is equal: each would have had an average CO2 output per passenger of 0.81 Kg.

And if the bus then runs many routes through the rest of the day, mostly empty, but kept working because the driver and capital costs have been paid, the average CO2 output per passenger for the bus will be much greater when taken across the whole day’s operations.

This might seem like an academic exercise, because the car was not a carpool. However, in the debate about whether carpools should be allowed on the North Shore Busway, it might be useful to recognise that the ‘buses are greener’ argument should not be accepted without some deeper analysis.

END

© Scoop Media