To Capitol Hill fanfare, the American Public Transportation Association released its new study, Public Transit’s Contribution to U.S. Greenhouse Gas Emissions on September 26.. The report is full of the usual big numbers for transit’s role in reducing greenhouse gases (GHGs). As is typical for reports covering the insignificant, the big numbers are never related to the much larger base of GHGs from personal transportation. If one believes the APTA numbers (which one does not, see below), transit use saves approximately 0.5 percent of GHGs attributable to personal transportation (cars, personal trucks or SUVs and transit).
There are problems even with that number. More than 40 percent of the “savings” is an exaggerated estimate of the congestion reducing GHG reductions of transit. There is no doubt that, without transit use, there would be more congestion near the cores of the nation’s largest downtown areas (Manhattan, Chicago’s Loop, Boston, Philadelphia and San Francisco, for example), but the impact would be slight in the rest of the county (places like Portland, Phoenix and perhaps Paducah), where the great bulk of the nation’s traffic congestion delay occurs. Randal O’Toole and I showed a similar estimate to be highly exaggerated in a Heritage Foundation paper The Contribution of Highways and Transit to Congestion Relief: A Realistic View three years ago.
All in all, a more reasonable figure for transit’s contribution might be 0.3 percent. Even that may be high. The APTA research only counts energy for propulsion (movement). Some estimates place the energy consumption at transit rail stations and maintenance facilities at a third above the propulsion figure.
But that opens a whole new area of inquiry --- full cost accounting of greenhouse gas emissions,. A full life-cycle accounting would include GHG emissions from construction of transit and highway systems, construction of vehicles, extraction of fuel for electricity generation and refining, disposal of vehicles and other materials, vehicle maintenance and administrative support.
However, the news out of APTA is not that transit saves so much in GHGs. It is rather that, even with exaggeration and an apparent error, it saves so little. And things will get worse. The United States might be thought of as two nations in transit --- New York and the rest of the country. In New York, transit plays a far more substantial role than anywhere else.
Predictably, transit in New York is very GHG friendly. New York’s GHG emissions are well less than one-half that of transit elsewhere (and cars).
Outside New York, the average automobile (not SUVs) is just about as GHG friendly as transit (see Greenhouse Gas Emissions: US Public Transport and Personal Modes).
However, even New York’s advantage may be fleeting. Cars are becoming more fuel efficient, which is indicated by the hybrid and hybrid diesel data. Toyota’s Prius produces only 10 percent more GHGs per passenger mile than transit in New York. Hybrid diesel cars just entering the European market emit 22 percent less.
So, as for transit’s contribution to GHG reduction --- interesting, but no big deal.