Even if more subsidies to transit could attract significant numbers of people out of their cars, it would not save energy or reduce greenhouse gas emissions because transit uses as much energy and generates nearly as much greenhouse gas per passenger mile as urban driving. As described in my Cato Institute Policy Analysis no. 615 (https://www.cato.org/pubs/pas/pa-615.pdf), the following data are based on the Department of Energy’s Transportation Energy Data Book, the Federal Transit Administration’s National Transit Database, and the Federal Highway Administration’s Highway Statistics.
In 2006, the nation’s transit systems used an average of 3,444 BTUs and emitted 213 grams of CO2 per passenger mile. The average passenger car used 3,445 BTUs‐just 1 BTU more‐and emitted 245 grams of COsup>2 per passenger mile, just 15 percent more. While transit appears slightly cleaner than autos, as shown in figure three, auto and light truck energy efficiencies have rapidly improved, while transit energy efficiencies have declined. Since CO2 emissions are proportional to energy consumption, these trends hold for greenhouse gas production as well.
We can expect these trends to continue. If auto manufacturers meet the Obama administration’s new fuel‐economy standards for 2016‐even if they fail to improve energy efficiencies beyond that‐by 2025 the average car on the road will consume only 2,600 BTUs and emit only about 186 grams of CO2 per passenger mile‐considerably less than most transit systems (figure four).
This rapid improvement is possible because America’s auto fleet almost completely turns over every 18 years. By comparison, cities that invest in rail transit are stuck with the technology they choose for at least 30 years. This means potential investments in transit must be compared, not with today’s cars, but with cars 15 to 20 years from now.
In much of the country, the fossil‐fuel‐burning plants used to generate electricity for rail transit emit enormous amounts of greenhouse gases. Washington’s Metrorail system, for example, generates more than 280 grams of CO2 per passenger mile‐ considerably more than the average passenger car. Light‐rail systems in Baltimore, Cleveland, Denver, Philadelphia, and Pittsburgh all emit more greenhouse gases per passenger mile than the average SUV.
In places, such as the West Coast, that get much of their electricity from renewable sources, it would be wiser and more cost‐effective to apply that electricity to plug‐in hybrids or other electric cars that can recharge their batteries at night when renewable power plants generate surplus energy. As Professor Lave said, the “law of large proportions” dictates that “the biggest components matter most.” In other words, since more than 90 percent of urban travel is by auto and only 1.6 percent is by transit, small improvements in autos can be far more significant than large investments in transit.
Transit has several other disadvantages as a way of reducing greenhouse gas emissions. First, even where electric‐powered rail transit generates less greenhouse gases than cars or buses, the trains are supported by feeder bus systems that emit lots of greenhouse gases. While the trunk line buses that new rail transit lines replace typically run fairly full, the feeder buses that support rail transit run fairly empty because many rail riders drive to transit stations. The result is that greenhouse gas emissions on many transit systems increase after opening rail transit lines. After opening its first light‐rail line, CO2 emissions from St. Louis’ transit system climbed from 340 to 400 grams per passenger mile, while Houston’s grew from 218 to 263 grams per passenger mile.
Construction of rail transit also consumes huge amounts of energy and releases enormous amounts of greenhouse gases. Portland planners estimated that the energy cost of constructing one of the city’s light‐rail lines would equal 170 years worth of energy savings.
Highway construction also generates greenhouse gases, but because highways are much more heavily used than most rail transit lines, the emissions per passenger mile are far lower. Contrary to claims that rail transit can carry as many people as four or more freeway lanes, the New York City subway is the only rail transit line in America that carries more passenger miles per rail mile than one urban freeway lane mile. Outside of New York, the average urban freeway lane mile carries 12 times as many passenger miles as the average commuter rail mile, 7.5 times as many as the average light‐rail mile, and 2.4 times as many as the average subway/elevated mile.
Further, as we tragically learned in the recent Washington Metrorail crash, rail transit systems must be completely rebuilt or rehabilitated every 30 years or so. The energy costs and greenhouse gas emissions from such reconstruction must be taken into account when considering rail transit. As a recent Federal Transit Administration report calculated, rehabilitation of rail lines in the nation’s seven largest transit systems will cost at least $50 billion‐money those agencies don’t have. This is just one more indication that rail transit is not financially sustainable.
In the rare case where a transit investment really will reduce greenhouse gas emissions, the cost is exorbitantly high. McKinsey & Company says the United States can cut its greenhouse emissions roughly in half by 2030 by investing in technologies that cost no more than $50 per ton of CO2 equivalent. But transit investments, if they reduce emissions at all, do so at costs of $5,000 per ton or more.