Traffic congestion: Meaning (information, definition, explanation, facts)

Traffic congestion is the level at which transportation system performance is no longer acceptable due to traffic interference. High lane occupancy percentages indicate congested conditions. The U.S. Department of Transportation uses the following scale to define traffic congestion based on lane occupancy:

• 35% or higher: Stop and Go
• 22% - 35%: Heavy
• 15% - 22%: Moderate
• 0-15%: Wide Open

As population increases, the demand for highway travel, and along with that traffic congestion, increases as well. Construction of new highway capacity to accommodate this growth in travel has not kept pace. Between 1980 and 1999, route miles of highways somewhere increased 1.5 percent while vehicle miles of travel there increased 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 21.6 billion liters (5.7 billion gallons) in wasted fuel and $67.5 billion in lost productivity. With traffic volumes projected to continue to grow, traffic congestion is a problem in the big cities but delays are becoming common in smaller cities and even in rural areas.

The five areas showing the highest congestion levels were: Los Angeles (1.57), Washington, DC (1.43), Miami-Hialeah (1.34), Chicago (1.34) and San Francisco-Oakland (1.33). Cities with the lowest congestion levels were: Bakersfield, California (0.68); Laredo, Texas (0.73); Colorado Springs, Colorado (0.74); Beaumont, Texas (0.76); and Corpus Christi, Texas (0.78). While San Diego and Las Vegas saw their congestion levels increase by more than 50 percent since 1982, conditions worsened at the same rate in three smaller cities: Salt Lake City, Utah; Albany-Schenectady-Troy, New York; and Eugene-Springfield, Oregon.

Attempts to alleviate traffic congestion include:

• Road pricing such as the London Congestion Charge, a fee levied on vehicle drivers entering the centre of the city
• Free public transport offered by the local or provincial government, see Public transport#Funding
• Setting of school opening times to avoid problems associated with the school run
• High-occupancy vehicle lanes or "carpool lanes"