Hoping to reduce traffic congestion and air pollution, US urban areas from Los Angeles to Sioux City (Iowa) are rushing to build new surface light rail systems. But despite claims to the contrary, light rail does not reduce traffic congestion, and is a highly expensive strategy..

US federal research indicates that quality bus systems are one-fifth the cost per passenger mile of light rail per passenger mile, can accommodate the volumes and operate as fast. Offering no speed or capacity advantage over buses, new light rail systems are simply obsolete, like the latest advancement in horse cars.

In contrast, grade separated metros (undergrounds and elevateds) and suburban rail may offer advantages over bus systems where passenger volumes are exceedingly high and trip destinations very concentrated. These more rapid urban rail alternatives play an invaluable role in the world's largest and most dense central business districts, such as New York, Tokyo, Paris, London and Hong Kong. But implementation of such intense rail strategies is inappropriate in the low density US urban areas. Costs are too high, at up to $300 million per mile for metros, and demand for suburban rail is scant that new riders could be leased a car more inexpensively.

Over a decade ago, a US federal government study by Don Pickrell found that new light rail lines carried only a fraction of their projected ridership. But there is a more fundamental issue. However high the ridership projections, they never rise to significance in comparison to automobile travel volumes. Few automobile drivers are attracted to light rail systems, and traffic congestion has not been materially reduced in any corridor. This is not surprising. Planning studies that justify new light rail virtually always predict at best nominal results. This facts do not, however, deter light rail aficionados, who relentlessly mislead the public to believe that light rail reduces traffic congestion and air pollution, suggesting that up to 12 lanes of freeway traffic will be carried. This is absurd. In the United States, new light rail lines carry, on average, less than one-quarter the volume of the a single freeway lane. Misrepresentation of this magnitude would violate consumer protection laws in the commercial sector.

Since light rail does not reduce traffic congestion, it cannot reduce air pollution. The great advances in clean air have resulted almost completed from improved on -board automobile technology.

Advocates also claim that light rail is less costly than new highways, This is alleged by comparing the cost of a light rail line per mile to that of a six or eight lane freeway. This is an invalid, because the freeway carries such an enormously greater number of people. An eight lane freeway carries, on average, 16 times the volume of a new light rail line. In fact, total costs, public and private, per passenger mile of light rail averages seven times that of new urban freeways. This does not mean that new freeways should be cut through American cities. It is, however, testimony to the fact that light rail and traffic congestion are wholly unrelated subjects. It should be added that new light rail's failure to impact traffic congestion does not provide an argument for tearing down the systems that exist.

Light rail's shortcomings are part of a larger transit problem. No form of transit can replace the automobile for most trips in American urban areas. Automobile competitive transit --- service that is quick, frequent and operates throughout the day --- is simply not available, except for a small fraction of trips. Typically that is limited to central business district (CBD) destinations. Transit carries a sizeable work trip market share only to the largest such downtown areas. For example, 75 percent of commuters to New York's CBD travel by transit, while transit shares exceed that of the automobile in six other CBDs. Elsewhere, however, CBD transit market shares are much smaller. Worse, CBDs have fallen sharply in recent decades, as new employment growth has been in the suburbs. Now, CBD's represent, on average, less than 10 percent of metropolitan employment. Thus, for more than 90 percent of work trips, and an even larger percentage of other trips, transit simply provides no product in the market., Transit's impact on traffic congestion is limited to corridors leading to the largest CBDs, where its market share has been high, though stagnant or declining, for decades. Overall, public transit's work trip market share is under four percent and its share of urban travel is two percent.

To significantly increase the percentage of the travel market for which public transit competes would take massive service increases and budgets that are simply beyond comprehension. For example, European urban areas provide 15 times higher service intensities (vehicle miles per square mile) to produce market shares ten times greater. Asian cities provide 70 times higher service intensities, while attracting 20 times the market share.

There are two reasons that transit cannot compete in the US. First; urban population densities are too low --- approximately one-fifth that of European and one-fifteenth that of Asian urban areas. For example, Portland (Oregon), with 1.5 million residents, strains to claim (wrongly) success for its densification policies. Yet, at Hong Kong densities, Portland would house 45 million people, at Tokyo densities 10 million and at Paris densities five million.

Second; and just as important, US urban areas are too decentralized. European CBDs tend to have regional employment market shares more than double that of those in the US. Lower densities and greater decentralization make automobile competitive transit all the more difficult.

Why, then, is light rail being built in the United States? First and foremost, the federal government has made billions of dollars available and cities have great incentives to obtain the money. They would wrestle as quickly to build monoliths, were federal funds available. Then there is the perception that light rail, like large convention centers and domed or retro athletic stadia, qualifies a city as "world class." Former Harvard Economist John Kain characterizes it as boosterism. Seattle bicycle commuter and anti-rail activist Emory Bundy has likened it to cigarette advertising strategies that seek association with a macho image (read" "world class city").

Despite their transit unfriendly environments, US cities are blessed with effective transportation systems. Traffic moves 50 percent faster than in Europe and double that of Asia. Work trips are 15 percent shorter than in Europe and a third less than in Asia. Traffic densities are a third less than Europe and half that of Asia. In consequence, air pollution is 20 percent to 80 percent lower. Australian cities, with similar characteristics and very low densities exhihbit the same characteristics. These higher quality of life characteristics result from dispering traffic over a wide, less dense area. With this performance, the so-called "smart growth" that would increase densities could not be more wrong-headed.

The situation may be little better for new light rail outside the US. It is likely to cost more than bus strategies, while providing no advantages. Every day, Curitiba, Sao Paulo and Porto Allegre carry busway volumes comparable to the best surface light rail lines. Where transit officials are maximizing ridership and the good transit can do in the community, there will likely be no role for new light rail.