Congestion is a growing concern on the nation’s transportation system. Not only does congestion make driving more inconvenient and unsafe, but it increases transportation costs for many American businesses. The Texas Transportation Institute (TTI) estimates that in the 68 metropolitan areas studied in 1997, Americans wasted 6.7 billion gallons of fuel and 4.3 billion hours of time because of delay. The total cost to American motorists in these areas is about $72 billion annually.

Travel (DVMT) per lane mile has increased on all systems over the past 10 years. While DVMT has grown for both rural and urban highways, it increased at a faster rate on rural routes. DVMT grew by 3.40 percent on rural Interstates between 1987 and 1997.

Another way to measure operational performance is to examine peak-hour travel equal or greater than the 0.80 volume-service flow (V/SF) threshold. This measures only the severity of peak-hour congestion, not its extent or duration. More than half of peak-hour Urban Interstate travel occurs under congested conditions.

Delay increased on all highways between 1993 and 1997, rising from 8.3 to 9.0 hours per 1000 VMT. While calculated delay declined on most urban highway systems from 1995 to 1997, the reason for this is unclear. A longer time period is needed to determine if this is the beginning of a trend. Daily delay is measured by hours per thousand vehicle miles traveled, and it primarily occurs in urbanized areas (over 50,000 population).