Many people assume public transportation is vastly more energy efficient than cars, and that spending more money on transit will attract people out of their cars.
In 1979, University of California-Irvine economist Charles Lave showed in the Atlantic Monthly that both of these assumptions were wrong. Persuading people to buy more fuel-efficient cars is easier and saves more energy, Lave found, than trying to get them to ride transit.
Today, transit advocates argue we need to spend more money on transit, and in particular rail transit, to reduce greenhouse gas emissions as well as save energy. Yet Lave's points are more valid than ever.
Driven by higher gas prices, America's auto fleet today is almost 40 percent more fuel efficient than in 1979. In contrast, the energy efficiency of both bus and rail transit has declined as transit services have reached into distant suburbs, where few people use transit. Despite investing hundreds of millions of dollars into light rail, the share of St. Louis-area commuters using transit has actually declined to 2.8 percent today from 6.9 percent in 1979.
Metro's buses today consume more energy and emit more greenhouse gases, per passenger mile, than a typical sport utility vehicle. Its light-rail lines do better, but consume almost as much energy, and emit almost as much greenhouse gas, per passenger mile, as the average car.
Moreover, even where rail operations do save energy, this savings almost never makes up for the huge energy cost of rail construction. Highway construction also consumes energy, but because highways are more heavily used than rail lines, their energy cost per passenger mile is far lower.
If we ignore construction costs, many rail operations do consume less energy than the average auto — but almost none consume less than a Toyota Prius. As Lave suggested in 1979, to save energy and reduce greenhouse gas emissions, it is far more cost effective to encourage people to drive more fuel-efficient cars than to build rail transit lines.
Transit agencies that want to save energy and reduce greenhouse gas emissions should focus on increasing bus loads or reducing the size of their buses. The average Metro bus has 39 seats, yet averages less than 10 passengers. Concentrating service in areas where loads are higher, and using smaller buses in areas or times of day where loads are lower, will do far more to save energy than building rail transit.
Transit agencies also could consider alternative fuels. Hybrid-electric buses save far more energy per dollar invested than the most efficient rail systems.
Electrically powered rail or bus systems reduce greenhouse gas emissions only if they rely on hydro or other renewable sources of energy. Because most of Missouri's electricity comes from coal, electric-powered transit actually generates as much greenhouse gases per passenger mile as transit powered by gas or diesel.
Cities that want to save energy should focus on the form of transport people use the most: automobiles. As Lave notes, "the biggest components matter most," so improving the mode that moves 95 percent of people will do far more than the mode that moves only 1 percent to 2 percent of people.
The most important thing cities can do is relieve congestion. The Texas Transportation Institute estimates that urban congestion wastes nearly 3 billion gallons of fuel each year, in turn emitting 28 million tons of carbon dioxide. This has more than quintupled since 1982.
One simple way to relieve congestion is to coordinate traffic signals. The Federal Highway Administration estimates that three out of four traffic signals need updated coordination systems. Signal coordination costs little, yet can save huge amounts of time, fuel and emissions.
Another way to relieve congestion is to build new roads and pay for those roads with tolls that vary by the amount of traffic on the roads. Variable tolls can keep roads free flowing at all times, saving both energy and greenhouse gases.
There may be places in the world where rail transit works. There may be reasons to build it somewhere in the United States. But saving energy and reducing greenhouse gas emissions are not among those reasons. Missouri cities that want to be green should look to other strategies that are far more cost-effective than investing in high-cost rail systems.