The Texas Department of Transportation (TxDOT) released its 2011 edition of the 100 most congested roadways list Sept. 1, and the results are not surprising — congestion remains a daily challenge for motorists in Texas metropolitan areas.

With a few exceptions, the 2011 list is much the same as last year’s. The differences are likely the result of slower traffic speeds because of prolonged weather events, lane closures related to recent construction projects or faster speeds resulting from the completion of road or bridge improvements, according to a written statement from TxDOT.

As in previous years, nationally recognized traffic congestion experts with the Texas Transportation Institute (TTI) at Texas A&M University worked with TxDOT to analyze congestion levels and develop the list.

“Finishing or starting construction is probably the number one reason for the shift in ratings,” said Dr. Tim Lomax, a research engineer with TTI, who coordinated with TxDOT staff to develop the list. “Weather contributed, and the economic recession has generally reduced congestion compared to four years ago, but in the last year, construction was primary.”

Dr. Lomax added in the TxDOT written statement that congestion levels are higher on certain highways, probably because of lane closures on new construction projects. In other areas, construction projects were completed and the improvements caused a fall in the rankings.

Analysis for the top 100 list includes the state highway system and many city, county or toll road segments. Additionally, it considers both weekday and weekend congestion levels to provide a congestion ranking based on delay experienced all days of the week.

Any change that slows or speeds up traffic is reflected in the final results, Dr. Lomax noted.

“It’s definitely a testimony to how many Texas roads are congested when small changes in peak speeds result in significant shifts in rankings,” he said.

In 2010, the state switched from using estimates of congestion based on traffic density to calculating congestion levels based on actual traffic speeds. The same method was used to develop the 2011 list. The result is a more precise analysis of traffic delay and congestion. The more accurate data also identifies problems such as bottlenecks caused by intersecting roadways or poor roadway geometry.