If your trucks aren't showing up on schedule, it's probably because they're stuck in traffic. According to the "2004 Urban Mobility Report," issued by the Texas Transportation Institute (TTI), growing traffic congestion in cities of all sizes is affecting both motorists and motor carriers more than ever.

TTI's research team estimated that traffic congestion cost the nation some $63 billion in 2002. One reason: Idling cars and trucks stuck in traffic jams wasted 5.6 billion gallons of fuel that year. The study's authors drew their conclusions by comparing federal and state highway data from 1982 to 2002 for 85 urban areas with populations exceeding 500,000.

In 1982 about one-third (34 percent) of the national road system was congested, amounting to .7 billion hours of delay. In 2002, congestion affected 58 percent of the highway network, resulting in 3.5 billion hours of delay.

Which is the most congested city in America? TTI awarded that dubious honor to the Los Angeles–Long Beach–Santa Ana area, which experienced 625,063 hours of travel delays. The New York–Newark, N.J., area came in second, with 394,709 hours. The least-congested city was Brownsville, Texas, at 413 hours.

The problem of congestion has grown too complex for any one solution to resolve, the authors said. In addition to more road construction, they suggested, governments could manage demand by better promoting carpools and public transportation. They also could use pricing incentives to discourage road use during peak periods.

As for the future of traffic congestion in America, the TTI team foresees more of the same. "If we're lucky enough to sustain this growth, and the funding levels and options do not increase from the current trends, we shouldn't be surprised if we see even more congestion," said Tim Lomax, one of the study's authors.