How we measure commuters' misery
Saturday, January 22, 2011; 5:24 PM
When advocates for transportation improvements want to illustrate how bad the commute has gotten, they almost always cite their region's high ranking in a national study of congestion prepared by the Texas Transportation Institute. Tim Lomax, a researcher with the institute, recognized the benchmark status the organization's Urban Mobility Report has gained when he characterized it as "the second slide" in many transportation presentations, coming right after the title page.
With such an important role to play, the report has developed its share of critics. They question its methodology and conclusions about where we stand and what we should do next.
The debate reflects a fundamental issue for commuters: When we try to measure our commuting misery by the numbers, what values should we look at and what goals should they reflect?
Urban Mobility Report
The latest version, released last week, continued a depressing trend for the D.C. region. By any of the various measures of mobility, we don't have it. In fact, our congestion and delays are among the worst for very large urban areas, based on the 2009 statistics. Here's a summary of our key nationwide rankings .
Travel Time Index: No. 2
This measure of congestion focuses on each trip and each mile of travel. It is a ratio of travel time in peak periods to travel time in free-flowing traffic.
Delay per peak auto commuter: No. 1
This is a yearly sum of delays for people who drive in the peak periods of 6 a.m. to 10 a.m. and 3 p.m. to 7 p.m. It illustrates the effect of per-mile congestion as well as the length of each trip, the report says. We tied with Chicago.
Delay per non-peak traveler: No. 1
This measure reflects annual extra travel time for people during midday, evening and weekends.
Congestion cost per peak commuter: No. 2