Press Release

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Researchers identify the nation’s most congested corridors in first nationwide effort to quantify travel reliability problems

For release:

12:01 a.m. CST,
Tuesday, November 15, 2011

For more information:
Bill Eisele
Research Engineer
Texas Transportation Institute
(979) 845-8550

David Schrank
Associate Research Scientist
Texas Transportation Institute
(979) 845-7323

Holiday travelers will have a better idea of exactly where to expect traffic delays, as well as some help in planning for them, thanks to a report released today by the Texas Transportation Institute (TTI), a Texas A&M University System agency.

The 2011 Congested Corridors Report is the first nationwide effort to identify reliability problems at specific stretches of highway responsible for significant traffic congestion at different times and different days. Researchers noted that the corridors included in the report were identified by the data itself.

INRIX, a leading provider of traffic data and analytics, originated the corridor approach, using 10 hours of congestion per week to define a starting point for a congested corridor. To be considered a “corridor,” according to the INRIX standard adopted for this report, congestion should impact a freeway segment at least 3 miles long.

“Until now, we’ve been able to measure average congestion levels,” noted TTI Research Engineer Bill Eisele, “but congestion isn’t an ‘average’ problem. Commuters and truckers are understandably frustrated when they can’t count on a predictable trip time from day to day.”

Eisele credited the data and corridor listing provided by INRIX with making it possible for researchers to quantify traffic congestion, and the even more frustrating variation in congestion from day to day in major urban areas across the country.

The report describes congestion problems in 328 seriously congested corridors over a variety of times — all day, morning and evening peaks, midday, and weekends. Much of our national congestion problem exists in a relatively small amount of our freeway system.

Not only were these roads found to have more stop-and-go traffic than others, they were also much less predictable — “so, not only does it take longer, commuters and truckers have a difficult time knowing how much longer it will take each time they make the same trip” said co-author David Schrank.

Among the report’s key findings:

  • The 328 corridors, while accounting for only 6 percent of the nation’s total freeway lane-miles and 10 percent of the traffic, account for 36 percent of the country’s urban freeway congestion;
  • The 328 corridors account for 8 percent of the national truck traffic and 33 percent of urban freeway truck delay;
  • Travel time reliability is more of a problem around bridges, tunnels and toll facilities, both because there are few alternate routes available in such circumstances and because a small incident can have a huge effect on corridor travel times;
  • When travel time variability increases, your trip becomes less predictable. Every occurrence of an unpredicted travel disruption creates slower speeds than normal and contributes to an increase in our reliability measures.

As the first national look at travel time reliability, researchers believe that the report can be useful in determining where transportation system improvements will have the greatest impact.

The best approach is to consider all the congestion solutions:

  • Traditional road building and new or expanded transit facilities;
  • Traffic management strategies such as aggressive crash removal;
  • Demand management strategies like improving commuter information and employer-based ideas such as telecommuting and flexible work hours; and
  • Denser development patterns with a mix of jobs, shops and homes so people can walk, bike or take transit to more and closer, destinations.

The researchers stress that there is no single best way to fix the problem. The best solutions, they say, will come from efforts that have meaningful involvement from everyone concerned — agencies, businesses and travelers.

“If cities and states make the right investments in our most congested highway corridors, the return on those investments will be substantial,” says study author Tim Lomax. “Not only will we see more reliable trips for travelers and trucks, but we can also expect to see greater productivity and more jobs.”

The Texas Transportation Institute, located in College Station, Texas, is an agency of the Texas A&M University System.