Traffic Study Offers Safe Design Alternatives for KDOT

There were safety concerns at the intersection of US-75 and K-9 in Jackson County, Kansas. Some of these included poor sight distance, near-miss crashes, and difficulty maneuvering through the intersection due to the skew. The Kansas Department of Transportation (KDOT) asked our traffic team to study the area to assess the current state, project future volumes, and advise as to possible solutions.

We were tasked with collecting traffic volume and speed data at the intersection. The volumes were then projected to a future 20-year time frame. KDOT also provided 5-year crash history at the intersection for review and analysis. We also performed a Highway Safety Manual review of the existing intersection and possible improvement options.

After the data was collected, reviewed, and analyzed, we provided KDOT with a list of low, medium, and high-cost options to improve safety and operations at the intersection. The high-cost options were broken down into three classifications: intersection relocation, roundabout, and interchange. At least two preliminary layouts were prepared for each classification.

As we developed designs, an existing grain elevator in the southeast corner of the intersection posed a challenge. Avoiding this property greatly limited the options south of the existing intersection. We also had to work around an existing cemetery located approximately one-half mile southeast of the intersection, along Highway 9.

KDOT reviewed our layouts and selected the preferred option for each classification. A planning level construction cost estimate and benefit/cost analysis was completed by our team for each one. Next, we prepared a draft report that documented the data collection, analysis, and recommendations. After it was submitted, a meeting was held with the KDOT Secretary and upper management to discuss the report and recommendations. Finally, we integrated their feedback and generated a final version.

To improve the safety of this intersection, we provided a number of options. A medium cost recommendation suggested the installation of northbound and southbound left turn lanes on US-75. This would provide a space for turning vehicles to safely wait to complete their turning movement, while out of the high speed through lane. The recommended high-cost intersection relocation option would relocate the intersection approximately 250 feet north and eliminate the intersection skew. This in turn should improve the safety at the intersection.

With the traffic study complete, KDOT can begin to make plans. Having layouts, data, and estimated costs allows them to more easily work infrastructure improvements into their budget and workflow. We look forward to seeing how their next steps translate to safer roadways in the future for residents.