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CTR/UTSA Team Provides Legislative Tools to Texas

With an increasing demand for Texas products around the world, a growing economy, and NAFTA, we continue to see increases in truck freight volume, tonnage, and value on Texas highways. As freight tonnage increases, decision-makers must decide if passing legislation and developing policies to permit heavier trucks to operate will improve the efficiency and competitiveness of the Texas economy. However, increased truck weight also means accelerated pavement and bridge consumption that must be addressed with increased maintenance funding.

To address these questions well ahead of the 2017 Legislative Session, TxDOT’s State Legislative Affairs (SLA) Section initiated a study in early 2016 that combined the forces of CTR and the University of Texas at San Antonio (UTSA). The study purpose was to conduct two formal workshops with the trucking industry and hold one-on-one meetings with selected industry groups. In addition, the study team analyzed the trucking industry’s proposals for new truck sizes and weights. The work resulted in the SLA Truck Configuration Library, which provides information on each analysis. The SLA Section and TxDOT subject matter experts from the Maintenance and Bridge Divisions worked closely with CTR faculty, researchers, and graduate research assistants (GRAs) as well as UTSA faculty and researchers. This study team provided TxDOT and lawmakers with new methods for evaluating the impacts of increased truck size and weight to Texas pavements and bridges.

About the SLA Truck Configuration Library
The SLA Truck Configuration Library makes essential data on truck types and consumption rates more accessible to policy-makers. Specifically, the Library stores and displays data and analysis findings for selected truck types, sizes, and configurations, and Library provides the analyzed truck dimensions, load distribution, and consumption rates for pavement and bridges.

SLA Truck Configuration Library slides

Example screen

The information concerning pavement and bridge consumption rates helps legislators determine permit fees for overweight and oversized trucks. Since accelerated bridge and pavement consumption also means increased revenue needed for repairs, permit fees are important since they can help partially recuperate these increased costs of operation.

Example of configuration results

Example of configuration results

Project researchers included CTR’s Michael Walton (study director); Jorge Prozzi (pavements); Michael Murphy (configurations); Hui Wu (SLA Truck Configuration Library); Nan Jiang (data analysis); Lisa Loftus-Otway (legal inquiries); Robert Harrison (economics and future trends); and CTR GRAs Manar Hasan, Hongin Xu, and Swati Agarwal (Load Xpert Analyses and analysis support). In addition, UTSA’s Jose Weissmann and Angela Weissmann conducted analyses of bridge structures. All team members participated in workshops; coordinated one-on-one meetings with specific industry representatives; and conducted field trips to collect data.

“The Senate bills originally introduced in 2015 would have had a much greater impact on pavement and bridge consumption due to lack of clear language in the bills to specify the axle, axle group, and gross vehicle weight load limits; the spacing between axles; and the permit fee rate compared to the infrastructure consumption rate,” Dr. Murphy states.

Thanks to the team’s research, however, the new truck size and weight bills for sealed ocean containers and milk tank trucks, which will become law in September 2017, contain language that helps retain the structural and functional condition of roadways. In addition, the consumption rate information provided to state legislators helped establish the permit fee levels for these heavier trucks—the fees will help fund maintenance for pavements and bridges that carry these heavier loads. For all the study results, read the project report [PDF]. To find out more about the library’s development, view this presentation [PowerPoint].

A Winning Combination
The CTR/UTSA study team has a history of successful collaboration, having worked closely together on other research projects with significant outcomes, such as 0-6736: Rider 36 Oversize/Overweight Vehicle Fees Study; 0-6820: A Process for Designating and Managing Overweight Truck Routes in Coastal Port Regions; and 0-6817: Review and Evaluation of Current Gross Vehicle Weights and Axle Load Limits. Over the course of those studies, this group of collaborators developed new analysis methods to calculate pavement and bridge consumption rates in terms of dollars per vehicle mile traveled—an approach used effectively for this freight legislation analysis.

Example of general information screen

Example of general information screen

During the course of this study, CTR’s Dr. Murphy obtained information about East and West Coast container operations and presented a variety of container chassis and container size combinations to the government and industry partners to illustrate the various possibilities for achieving the desired cargo weights while reducing infrastructure consumption.

According to Dr. Murphy, the goal of these discussions with industry was to understand how changes in operation could affect load distribution and a truck driver’s ability to adjust load among axles and axle groups. For the 2017 session, the research team used the Load Xpert computer program to analyze each proposed truck configuration to determine the axle and axle group distributions. (Load Xpert is a truck modeling and load calculation analysis software that allows users to create diagrams and visually configure most types of trucks. The program works in partnership with the Federal Bridge Formula, which instantly assesses potential loads and vehicles for road compliance.) This information was then provided to Dr. Jorge Prozzi and Drs. Jose and Angela Weissmann, who conducted pavement and bridge consumption analyses using models they developed through previous research.

Example of bridge consumption analysis

Example of bridge consumption analysis

Using Load Xpert along with collecting new data, the CTR team updated the SLA Truck Configuration Library based on three truck operational types: ready mix trucks, milk tank trucks, and ocean containers. The team also included a truck that demonstrated the maximum legal size and weight permitted in Texas and a complete Load Xpert analysis, along with variables that accounted for higher and lower levels of consumption.

“We also did extensive analyses of multi-axle ready-mix trucks and showed that some of the configurations included in the 2015 legislation could not be legally operated at the axle load limits requested,” Dr. Murphy states. “Based on our analyses performed through Load Xpert and presentations to the trucking and ready-mix industries, the industry decided to withdraw their requests for increased weight limits until further evaluations of their needs could be made.”

With freight demands, pavement materials, and bridge technology constantly evolving, the CTR/ UTSA research team’s work is far from over. However, by providing adaptable tools and resources for the public, they help pave a path to improving freight transport for future generations.


Posted by Maureen Kelly  |  Category : Bridges & Other Structures