2/7/12 – The Purple Line, Greenhouse Gases and the Environment

February 7, 2012
The Purple Line, Greenhouse Gases and the Environment


There’s no question that the Purple Line as currently planned will hurt our local environment – in more ways than just clear-cutting thousands of trees along the three-mile stretch of the Capital Crescent Trail between Bethesda and Silver Spring.

Sadly, politicians have chosen a railroad system over the more environmentally-friendly bus rapid transit (BRT) system option that was proposed. But it is not too late to change course and choose BRT.

Commenting on the draft environmental impact statement for the Purple Line, the World Resources Institute concluded that (medium investment) BRT was “the most cost-effective and lowest-risk” option, that BRT provided the “only alternative likely to reduce CO2 emissions” and that the light rail option – as chosen – “will increase CO2 emissions and very likely overrun current cost projections.”

The increase in CO2 emissions is significant – estimated to be 13,888 metric tons annually in 2030. Conversely, the BRT option for the Purple Line was estimated to reduce CO2 emissions by 8,883 metric tons annually in 2030. The Purple Line as planned is “green” in name only, as the net increase in the world’s major greenhouse gas – CO2 – is over 22,000 metric tons a year. To put it this real terms, that’s equivalent to adding 3,900 automobiles on the road for an entire year.

A second factor further illustrating how the present plan for the Purple Line harms the environment is this: when calculating emissions for the BRT option, planners assumed that buses would use diesel fuel and not natural gas, which emits 38% less C02 than diesel. In other words, a BRT system for the Purple Line using natural gas would make the net benefit equivalent to taking over 5,000 cars off the road annually.

But in fact, the environmental hazard of the present plan for the Purple Line may be understated. In considering the ridership of the Purple Line, planners used the national average of 22.4 passengers per mile for light rail and 8.7 for BRT, despite evidence that the per-passenger-mile rates would be much similar. This in turn painted a much rosier picture for the net reduction of cars from the road – and the emission of greenhouse gases – due to the light rail system.

To read the entire report on the Purple Line by the World Resources Institute, click on this link.