American taxpayers spend more than $40 billion a year subsidizing transit systems that are used by only a small fraction of urban residents. For many, the case for such huge subsidies rests on transit’s supposed environmental advantages: saving energy, reducing pollution, and cutting greenhouse gas emissions. This argument may have made sense in 1970s, when cars were gas guzzlers and heavy polluters while transit mainly served the dense cores of urban areas.
Since then, cars have become far cleaner and more energy efficient and will continue to do so in the foreseeable future. Meanwhile, transit systems have been extended to remote suburbs where few people ride transit, thus reducing average transit vehicle occupancies and making transit less energy efficient. While most rail transit is powered by electricity, in most states that electricity is generated mainly by fossil fuels. This means that even rail transit often pollutes as much and emits more greenhouse gases than driving.
In 2012, the average light truck used less energy per passenger mile than the average urban transit bus, while the average car used less energy per passenger mile than the average light-rail line. To really save energy, it would make more sense to get people into fuel-efficient cars like the Prius than to get them to ride transit.
The data show that the most energy efficient form of rail transit tends to be commuter trains, mainly because these tend to operate only during rush hours and thus are more likely to be full. Buses and trains that run all day long tend to be relatively empty during non-rush-hour periods, and even during rush hour they tend to be full only as they approach downtowns and other major job centers. Moreover, during rush hour buses and trains need to make round trips, and trips going opposite from the major direction of travel will tend to be relatively empty. This explains how trains that seem to be full during rush hour still end being only one-sixth full on average.
Transit advocate Todd Litman argues that rail transit is energy efficient during rush hour, when the trains are closer to being full. He claims that we shouldn’t count the fact that they run empty most of the time because they serve “other social purposes” such as providing mobility to low-income people who don’t have cars. Yet the same argument could be applied to every automobile trip, because–unlike some transit vehicles–every car on the road has someone in it who is going somewhere that is important to them and arguably supplies a valuable social good, whether it is getting kids to school, parents to grocery stores, or grandparents to medical centers.