Drivers in the nations most-congested cities should add 38 to 95 minutes to many routine 20-minute trips if they want to arrive on time, warns a new study on gauging unpredictable traffic.
For the Washington, D.C., area, the study says, drivers should set aside nearly two hours 114 minutes to arrive on time 19 out of 20 times. For the Dallas area, its 80 minutes and for San Diego, 58 minutes.
Fair warning, though: This applies only to the part of the trip on limited access roads, such as interstate highways, some toll roads and other roads that dont have traffic signals.
Thats from a new mathematical index offered Tuesday by the Texas Transportation Institute in its annual Urban Mobility Report, which analyzes congestion patterns in 498 of the nations urban areas to try to give motorists and shippers reliable driving times.
For the index, Institute researchers crunched data from INRIX, a traffic reporting service, the U.S. Transportation Department and state transportation departments.
When you have enough information about whats happening every day of the year, you can ... tell people how much extra time they should allow, said Tim Lomax, a co-author of the report.
He said reliable trip times are important for motorists when theyre going to the doctor, the airport or picking up a child at day care.
Theyre also important to truckers who transport goods. In 2011, trucks racked up $27 billion in congestion costs and some of that was passed on to consumers, the report says.
The institute found that in 2011, congestion caused Americans to travel 5.5 billion additional hours and purchase an extra 2.9 billion gallons of fuel for a congestion cost of $121 billion.
While congestion is below the 2005 peak, researchers say, its no cause for celebration: As the economy recovers, congestion will rebound.
The nation, Lomax said, is missing out on an opportunity to create a better-performing transportation system. He said the nation should invest in roads, bridges and urban transit now while construction costs are relatively low.
For the fourth consecutive year, the Washington area, including Northern Virginia, was the most congested urban area in the country. It was followed by Los Angeles, San Francisco and New York.
Washington, D.C., has the dubious distinction of being number one in two areas, said Pete Ruane, president and CEO of the American Road & Transportation Builders Association. It is the capital of partisan gridlock, and now traffic gridlock.
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