ICT/IDOT Propose the First Oversize/Overweight Permit Fee Structure Incorporating Safety Cost Analysis

Trucking is the lifeblood of commerce for the State of Illinois. In order to ensure the infrastructure of the state can safely support the movement of goods and services, the state regulates oversized and overweight (OSOW) vehicles, such as semis and large trucks, using a fee-based permit system. This fee system had not been evaluated, to ensure fees correspond to the effects OSOW vehicles have on infrastructure, for several decades. IDOT recognized that this system needed to be reviewed and possibly revised. In support of this, Illinois Center for Transportation (ICT) researchers used a variety of state-of-the-art techniques to sort through data and model the impact of OSOW vehicles on bridges, roads, and safety, in order to develop a fair, justifiable fee structure. The findings for the project, “Development of a Proposed Overweight Vehicle Permit Fee Structure in Illinois,” are now available on ICT’s web site.

The principle investigators for this project were Imad Al-Qadi, director of ICT and professor in the Department of Civil and Environmental Engineering at UIUC; Yanfeng Ouyang, professor in the Department of Civil and Environmental Engineering at UIUC; Hao Wang, assistant professor at Rutgers in the Department of Civil and Environmental Engineering; and Don Bell, engineer at TERRA Engineering. Dr. Al-Qadi, who called this project “timely and exciting” states, “I serve on the National Committee to evaluate the USDOT Truck Size and Weight Study and recognize the impact of overweight trucks on our transportation infrastructure. A fair fee can ensure the optimum service of our roads and bridges, which directly impacts the trucking industry. Driving on well-maintained roads reduces both fuel usage and wear and tear on tires and other truck parts.”

Flowchart of developed framework for bridge damage cost analysis

Overseeing the project’s Technical Review Panel was IDOT’s Justan Mann, Engineer of Construction Operations. As TRP Chair, Mann notes it is important to understand the financial impacts overweight vehicles have on the IDOT’s highway infrastructure.

Since parts of current fee structure had not been revised for more than 30 years, there were many challenges involved in the project. Some of the challenges arose out of the complexity of the system, the amount of available data, and the desire to incorporate safety impacts of OSOW vehicles. Before this project, Al-Qadi says, “there were no proper models that could relate the pavement and bridge service lives to overweight trucks quantitatively.”

The previous system relied only on bridge and pavement impacts of OSOW vehicles, and IDOT wished to also include safety data. As Al-Qadi states, “This was an exciting project. In addition to suggesting a quantitative and scientific-based fee formula for the use of roads and bridges in the state of Illinois, this is the first time that a fee related to safety has been incorporated.” In order to do this, the research team had to quantify the safety impacts of a variety of situations involving OSOW vehicles and use models to develop an estimation of the impact of an individual OSOW vehicle on traffic safety. This includes the monetary impact of accidents on both the infrastructure and the people involved according to Professor Yanfeng Ouyang, who led this part of the project.

The final step was to turn the model output into a fee recommendation. The final fee was taken to be a function of miles to be traveled, axel and weight information, and the accumulated fees from the model output. The final report details their findings and their recommendations to IDOT.

Flowchart of safety cost analysis

According to Mann, “The research team did an excellent job achieving the project’s goal of developing an equation that reflects the monetary impact OSOW loads have on highway infrastructure. IDOT’s next step is to compare fees calculated via this new equation with the existing fee structure through a large sampling of previous OSOW permits.”

Moving forward, Al-Qadi hopes to see this research lead to a mobile app that can help drivers optimize their routes as a function of pavement/bridge conditions and cost to user. He adds, “I want to recognize the other team members, including my colleagues Don Bell; Yanfeng Ouyang; Hadi Medani, for his work on the data reliability analysis; Hao Wang, for his work on the pavement damage models and corresponding fees; and the graduate students, including Kunjie Chen, Ziad Ghauch, Erman Gungor, Khaled Issam Hasiba, Antoine Petit, Junjie Qiu, and Jingnan Zhoa. We worked collaboratively with IDOT engineers, especially Justan Mann and Geno Koehler, to complete this timely project.”

Sample from the traffic estimation results