University of California Transportation Center

Traffic congestion is a vexing problem felt by residents of most urban areas. Despite centuries of effort and billions of dollars worth of public spending to alleviate congestion, the problem appears to be getting worse. Between 1980 and 1999, vehicle-miles of travel on U.S. roadways grew by 76 percent, while lane miles increased by only 3 percent. Average daily vehicular volumes on urban interstates rose by 43 percent between 1985 and 1999, from 10.331 million to 14.757 million. In a study of 68 urban areas published in 2001, the Texas Transportation Institute reported that the percentage of daily travel taking place during congested periods increased from 32 percent in 1982 to 45 percent in 1999; typical motorists faced seven hours per day of congested roadways in 1999 compared with five hours in 1982. According to the Federal Highway Administration, road delays (defined as travel time in excess of that at free flow conditions) increased by 8.5 percent between 1993 and 1997. Congestion also pollutes the air and wastes precious fuel.