SMART will be a net negative on greenhouse gas emissions

The SMART train, now under construction, was marketed to voters as a climate change solution, and a rough analysis of the initial operating segment seems to substantiate that claim. Unfortunately, the advantage evaporates with the inefficient second operating segment to Cloverdale. Critics have decried everything about SMART, but one of the most pernicious ones that has remained unexamined was the critique of SMART’s fuel efficiency. At only 1.1 miles per gallon of diesel fuel, the cars seem like the height of inefficiency. How could SMART claim its operations would reduce transportation greenhouse gases when it’s so clear it won’t?

SMART’s initial operating segment, from San Rafael to Santa Rosa, will serve 28.5 million weekday passenger miles every year and travel about 332,000 miles doing it.* At 1.1 gallons of diesel per mile, that means it will get about 42.8 passenger miles per gallon (pmpg). Since diesel emits more CO2 per gallon than gasoline, we’ll need to revise it down to the equivalent of 37.4 passenger miles per gallon (pmpg-e), roughly the same as a hybrid. Not bad.

According to MTC, cars’ fuel efficiency will get up to 32.2 mpg over the next 20 years. But this is the sticker value. Realistically, cars get about 13 percent less mileage than that (according to Consumer Reports), and in stop-and-go traffic it can be cut down another 40%. With 1.2 passengers per mile, that adds out to 26.9 pmpg during commute hours.

In other words, SMART will very likely emit fewer greenhouse gases than the cars its trips will replace, at least for the initial operating segment (IOS). The full line, however, won’t be quite so great.

The IOS is actually the most efficient part of the SMART line, at least according to official ridership figures. Adding extensions to Cloverdale and Larkspur will lower the train’s efficiency by quite a bit, to 26.3 pmpg-e. This is only as good as a car. We can cross off the full system for greenhouse gas emission reductions, at least if CAFE standards have anything to say about it.

Had SMART not been so financially constrained, it might have pursued electrification from the beginning, a $70 million investment that would have provided cleaner (and faster) service to the corridor.

This is not an indictment of the SMART system. It does not measure how the system will encourage people to swap car trips for walking trips, which happens when people use transit. It also does not take into account the annual mobility benefits for users, which will likely be worth hundreds of millions of dollars per year.

Indeed, individual transit lines are not meant to be climate change solutions on their own. They are like fax machines, enhanced by and enhancing other lines nearby. The accrued benefit of the network, as a whole, is enough to change how people live and travel. And that is what the SMART effort is about: not a final solution to our carbon footprint, but another link in the chain.

*People have complained that the Dowling ridership estimate was overoptimistic, and was not “accepted” by the SMART Board. Given that the latest numbers are used in financial planning and therefore underpin much of the financial structure of the system, I’m more confident in them than speculation from critics. However, if you wish to reduce ridership by some percentage, the precise weekday passenger miles estimate is 28,457,926 per year, assuming 265 working days.