New Data Analysis Facilitates Freeway Improvement Process
Written by By Pat Hawley, P.E., PTOE, RSP | raSmith
The Wisconsin Department of Transportation (WisDOT) undertakes comprehensive evaluations to determine the most beneficial roadway improvements before investing limited funds in projects. To enhance its data-driven approach, WisDOT partnered with two different teams, raSmith and Lakeside Engineers (AECOM served as a subconsultant on both teams), to conduct a safety and traffic operations analysis for the Southeast Wisconsin Freeway system, which is the busiest area in the state. The two teams merged their separate projects shortly after initiating their tasks to provide improved processes and outcomes for WisDOT.
The traffic safety analysis used Interactive Highway Safety Design Model (IHSDM) software for the evaluation of nearly every freeway corridor and system interchange in southeast Wisconsin. Traffic operations in several corridors were analyzed using Vissim microsimulation traffic flow modeling software.
This project included two main goals:
- Use the results of the safety analysis to compare one freeway corridor to another within the Southeast Region, including the system interchange ramps.
- Complete an alternative analysis to compare the baseline existing facility to a selected alternative(s), which will ultimately assist WisDOT with selecting a future project scope of work.
Unique Challenges
Prior to this project, Wisconsin had not used IHSDM software to evaluate safety and operational performance on a regional scale of this magnitude. The team faced many challenges in efficiently compiling the data in a way that was compatible with the software and would produce reliable results.
IHSDM and Vissim are data-intensive models, and the evaluation of 300 miles of freeway in the Southeast Region required a high level of data management. The IHSDM data included historic crashes, existing and forecast traffic volumes, and the geometric elements of each freeway segment. The Vissim data included existing and forecast peak period traffic volumes, origin-destination matrices, historic travel times, and freeway segment geometrics.
Another unique challenge revolved around the collaboration between project stakeholders. All three consultant firms (raSmith, Lakeside Engineers, and AECOM) worked closely with each other and WisDOT to solve challenges presented by the data, software, and variability in analysis methodology. The firms shared processes, best practices, and resources through each step of this complex project. Their collaboration helped ensure each freeway corridor was analyzed with the same methodology and assumptions for consistency.
Benefit-Cost Analysis
During the evaluation, the team determined the benefit-cost ratios for each roadway improvement design alternative. The ratios accounted for design and construction costs and factored in the socioeconomic benefits of reduced crashes such as personal and public property damage, injury, and loss of life. They could be compared to other alternatives for the same freeway segment, and each freeway segment could then be compared to other segments. The benefit-cost evaluation conducted in this project helped WisDOT to determine which alternatives were economical, benefitted the community, and supported its broader asset management goal.
Successful Results
The team accomplished all of the goals and objectives, completing the project on schedule and under budget. Throughout the project, coordination with the client and the full consultant team played a key role. This collaboration kept WisDOT involved in the process and apprised of any current challenges and how the team planned to work through them. The project was cost-effective because it allowed WisDOT to see the socioeconomic impacts of potential project alternatives. By focusing only on design alternatives that are economical and safe, the project provided a quality solution for the public.
About the Author
Pat Hawley, P.E., PTOE, RSP, serves as the assistant director of transportation services at raSmith. Pat has 30 years of transportation project management experience. His areas of expertise include traffic planning, access management, site circulation, traffic impact studies, roundabouts, and parking studies. raSmith is a civil and structural engineering and surveying firm. The company provides services on private sector projects across the United States and public sector projects in Wisconsin.