Growing congestion in the U.S. transportation network poses a substantial threat to the U.S. economy and to the quality of life of millions of Americans. According to the Texas Transportation Institute (TTI), in 2003, congestion in the top 85 U.S. urban areas caused 3.7 billion hours of travel delay and 2.3 billions gallons of wasted fuel, for a total cost of $63 billion 1. This figure would be substantially higher (perhaps almost triple) if it accounted for the significant cost of growing system unreliability and unpredictability to drivers and businesses, the environmental impacts of idle-related auto emissions, or higher gasoline prices. In the 10 most congested areas, each rush hour traveler "pays" an annual "congestion tax" of between $850 and $1,600 in lost time and fuel and spends the equivalent of almost 8 workdays each year stuck in traffic 1.
Highway congestion has increased dramatically over the past two decades. Between 1982 and 2003, U.S. highway congestion has increased in extent, duration, and intensity. In 2003, in the largest U.S. cities, highway congestion:
Congestion is also growing rapidly in small and medium-sized metropolitan areas. Based on current trends, a medium-sized city should expect its congestion in 10 years to be as bad, or worse than, that currently experienced by a large city. The rate of congestion growth has been greater in rural than in urban areas, portending increased congestion in communities of all sizes.
At its most fundamental level, highway congestion is caused by the lack of a mechanism to efficiently manage use of capacity. When searching for a solution to the congestion problem, most people immediately think of adding a new lane to an overburdened highway. Construction costs for adding lanes in urban areas average $10 million per lane mile. Generally, the funding for this construction comes from the tax that drivers pay when buying gas for their vehicles. Overall, funds generated from gas taxes on an added lane during rush hours amount to only $60,000 a year. This amount is grossly insufficient to pay for the lane addition. The bargain price paid by motorists for use of expensive new capacity encourages more drivers to use the expanded highway. Introducing congestion pricing on highway facilities discourages overuse during rush hours by motivating people to travel by other modes such as carpools or transit, or by traveling at other times of the day.