For the second year in a row, the Austin, Texas area ranked number 3 nationally in traffic congestion.  Austin is ahead of Houston and Dallas-Fort Worth, according to a study to be released today by Texas A&M University researchers.

In 2010, the year studied in the report, the Austin area had a “travel time index” of 1.28 , meaning that a rush-hour trip takes 28 percent longer on average than one in free-flowing traffic. That puts the area behind only metropolitan Los Angeles, at 1.38, and the Washington area, with an index of 1.33, and tied with New York City and the San Francisco Bay area.

Houston and Dallas-Fort Worth, with 1.27 and 1.23, respectively, have more acceptable traffic by that single measure from the Texas Transportation Institute, which is on the Texas A&M campus.

But Austin’s 2010 congestion index remains at its 2007 level and down from a peak of 1.32 in 2005 – the 70 miles of tollways that have opened in Austin’s suburbs since late 2006 may have had something to do with the change.

The study, which looked at traffic in more than 400 American cities, shows depressive effect on road congestion nationwide due to the economic downturn. The overall travel time index, which was 1.25 in 2005, is now at 1.20 . The authors of the 51-page study warn that when economic numbers rise, so will traffic congestion, absent aggressive construction of road and rail projects and other traffic mitigation efforts.

Austin, as in previous reports, fares better nationally on other congestion measures in the report.

The authors calculated a “commuter stress index” that looks only at the rush hour delay percentage in the main direction of travel (northbound on Interstate 35 from South Austin and Hays County in the morning, for instance, and southbound in the afternoon) and thus has higher numbers than the travel time index.

Austin’s stress index for 2010 is 1.38 , putting it at eighth in the country. Houston traffic has a stress index of 1.40 , according to the report.

Austin’s congestion cost, a measure that includes lost productivity and excess fuel from time spent idling in traffic, ranks 28th nationally, and the annual delay per commuter of 38 hours (about nine minutes per weekday) puts Austin at 15th .

Austin’s congestion is heavily influenced by the presence of I-35 and all the cross-country traffic that flows through Austin on it.  It also does not have down-town synchronized lighting like other major cities.

San Antonio, by contrast, fared much better with a travel time index of 1.18 , which ranked 26th nationally , and a commuter stress index of 1.27 , which ranked 28th nationally .