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Traffic congestion occurs when the volume of traffic on a roadway is high enough to become detrimental to its performance. In congested conditions, vehicle speeds are reduced, which increases drive times. These conditions are also more frustrating for drivers (see road rage), and automobile accidents may be more frequent. Furthermore, vehicles burn unnecessary fuel when stuck at idle. A period of extreme traffic congestion is known as a traffic jam.
In the United States, construction of new highway capacity has not kept pace with population increases and the resulting increase in demand for highway travel. Between 1980 and 1999, the total length of highways as measured by miles increased by only 1.5 percent, while the total number of miles of vehicle travel increased by 76 percent.
The Texas Transportation Institute estimates that in 2000 the 75 largest metropolitan areas experienced 3.6 billion vehicle-hours of delay, resulting in 5.7 billion gallons (21.6 billion liters) in wasted fuel and $67.5 billion in lost productivity. Traffic congestion is increasing in major cities, and delays are becoming more frequent in smaller cities and rural areas.
The five areas in the United States with the highest levels of traffic congestion are:
Additionally, residents of Atlanta, Georgia have an average commute of 35 minutes. This has been attributed to the large migration of people to the city and the fact that only 5 of the 28 counties that make up Metro Atlanta have any type of public transportation.
Due to dramatic population increases, San Diego and Las Vegas have seen their congestion levels increase by more than 50 percent since 1982.
The U.S. Department of Transportation uses the following scale, based on lane occupancy, to classify traffic congestion:
- 35% or higher: Stop and Go
- 22% - 35%: Heavy
- 15% - 22%: Moderate
- 0-15%: Wide Open
Attempts to alleviate traffic congestion
Last updated: 08-16-2005 15:12:53