Transit Environmental Benefits and Investment Priorities

The Moving Beyond Congestion project's Strategic Regional Transportation Plan Situation Analysis Interim Report Summary (that's a mouthful!) makes some assertions about the environmental benefits of public transportation. The Report states that the annual emissions reductions attributable to public transit "are equivalent to those produced by 3 billion auto vehicle miles." (Pg. 6) It also states that "assuming an average fleet fuel efficiency of 20 miles per gallon, the gasoline savings due to the RTA system is 150 million gallons per year." (Pg. 7)

Let's assume that these assertions are accurate. They make some sense because while transit vehicles are larger and burn more fuel than private vehicles, they usually carry multiple passengers (Pace buses sometimes excepted!). The multiple occupancy nature of transit vehicles make them more energy efficient and less polluting on a per passenger mile basis.

The Report seems to be making the suggestion that because on a per passenger mile basis travel on transit is better for the environment than travel in private vehicles investing billions of additional dollars in public transit is one of the best ways to deliver more environmental benefits for the region. Not so fast. Before investing those billions of new dollars into public transit to achieve those benefits, we need to determine if that investment is the best and most efficient way to deliver environmental improvements to the region. Are there alternative strategies that will deliver equal or greater environmental benefits per unit of investment?

Transit's small market share means that only a massive increase in that market share and/or dramatic improvements in the energy efficiency and emissions of transit vehicles will yield a noticeable improvement in the area's air quality. According to IDOT's 2005 Travel Statistics the six counties making up Northeastern Illinois (Cook, Lake, McHenry, Kane, DuPage, Will) generated 59,842,303,000 vehicle miles travelled by road in 2005. (Table FC-4) Let's make a very conservative assumption that every one of the vehicles covering these miles were single occupancy vehicles. This assumption that no car carriers more than one person results in 59,842,303,000 passenger miles by auto in the region. According to the National Transit Database, during 2005 the transit system (including vans and paratransit) generated 3,757,774 passenger miles, 5.9% of the region's passenger miles.

The Report claims that the emissions savings from transit are equal to those produced by 3 billion auto vehicle miles. Three billion vehicle miles equals only 5% of total vehicle miles in the region. Let's assume that we want to generate another 3 billion vehicle miles worth of emissions reduction. If we look to transit to deliver these benefits we will need to to double the number of transit passenger miles, essentially doubling the size of the region's public transit system. This will take levels of capital investment and operating subsidies far larger than those sought by the Moving Beyond Congestion initiative.

Alternatively, we could generate 3 billion vehicle miles of emissions reduction by reducing emissions from private vehicles by only about 5% (i.e., 60 billion annual vehicle miles x 0.05 = 3 billion vehicle miles). Surely, through a combination of regulation (e.g., increase vehicle mileage requirements), incentives (e.g., tax credits for hybrid vehicles) and smart fleet management (e.g., shifting taxis and government vehicles to hybrids) it should be possible to achieve 3 billion vehicle miles of emissions reduction more feasibly and at less cost than by doubling the passenger miles on the public transit system.

The same analysis also goes for fuel economy. The Report claims that the RTA system saves 150 million gallons a fuel each year assuming 20 miles per gallon fuel efficiency level. To derive another 150 million gallons of fuel savings we can shift 3 billion passenger miles from private vehicles to the transit system, which means a near doubling of the size of the current transit system. Alternatively, we can improve the fuel efficiency of the private vehicle fleet by only 5 percent (150 million gallons ÷ 60 billion annual vehicle miles/20 miles per gallon = 150m/3b = 5%). Surely it is possible to raise overall fuel efficiency by 5 percent more feasibly and at less cost than by doubling passenger miles on the public transit system.

Public transit does deliver substantial environmental benefits. But if our goal is to maximize environmental benefits, then focusing scarce capital and operating dollars on public transit may not make as much sense as using those resources to improve the fuel efficiency and reduce the emissions from private vehicles, which account for almost 95 percent of the passenger miles in the region. Even small improvements in those areas will dwarf the environmental benefits obtained from an unprecedented doubling in the size of the public transit system.