TH 22 is a key thoroughfare between St. Peter and East Mankato, Minnesota, and the heaviest trafficked section of two-lane highway in Minnesota Department of Transportation (MnDOT) District 7. While Highway 169 runs parallel to TH 22 and also connects St. Peter to Mankato along the City’s west side, TH 22 provides residents in St. Peter and along the corridor a more direct route to Mankato’s commercial corridor. Heavy traffic volume and the current configuration of TH 22 present several challenges to the community and the travelling public, including high crash rates and poor traffic flow. MnDOT engaged KLJ to help study possible reconfigurations.
MnDOT and KLJ conducted an initial visioning study to conceptualize options for expansion of the busy corridor. The team considered projected future traffic volumes, construction costs, and extensive public input to determine community needs. The study determined that a three-lane roadway with center turn lanes and passing lanes was the best alternative. Subsequently, KLJ conducted a corridor study to evaluate options for the proposed three-lane reconfiguration – such as traffic controls at the intersections – and determine which changes would most improve community safety and corridor operations.
The study broke from traffic engineering norms by using a Vissim microsimulation and surrogate safety analysis to evaluate 24-hour traffic along the corridor. The team used historical studies, crash data, and the Federal Highway Administration’s program Surrogate Safety Assessment Model (SSAM) to evaluate all the possible scenarios and potential conflicts along the corridor, and identify options that best mitigated crash risk. The team also met with business owners along the corridor to discuss the project, identify unique concerns, and devise creative solutions. They also evaluated options for passing lanes, studying whether they could improve, or at least maintain, travel times along the corridor, and ultimately identified optimal locations for new passing lanes.
The outcome of the study was an optimized plan to expand TH 22, including improvements that would decrease the cost of future crashes and delays by over 50 percent. The team provided plans for the design study and the construction project ahead of the design project, providing the project a valuable head-start, enabling required Right of Way acquisition to begin before the start of project design, and providing schedule flexibility as the project continued.
KLJ was awarded a “2022 Engineering Excellence Award” by The American Council of Engineering Companies of Minnesota (ACEC/MN) for our work on the Trunk Highway (TH) 22 Corridor Study project.