City of De Soto Increases Safety at 91st and Lexington

The intersection at 91st Street and Lexington Avenue is located near De Soto High School and a few commercial businesses. The area has significant traffic with K-10 highway nearby. During peak hours, it was a challenge for drivers to make a left-hand turn from 91st Street, and some were taking unnecessary risks. The City of De Soto, Kansas was looking for the best solution.

The intersection did not meet the engineering criteria needed to install a new traffic signal. Consequently, the City of De Soto began extensively studying the intersection, analyzing it in 2012, 2015, and 2018. The 2012 study suggested that installing a roundabout would improve traffic flow and safety.

Affinis was selected to design a roundabout for the area in June 2020. We began the project by meeting with the city and determining their needs. Then, we considered the constraints in the area. Because 91st and Lexington is close to a K-10 interchange, the Kansas Department of Transportation (KDOT) has right-of-way (ROW) near the site. BNSF, a railroad and a developer also had ROW here.

The city asked our team to avoid the BNSF railroad property when creating our design. They had worked with the railroad on a previous project and knew the rail line was lower than the road, which would add complexity to navigating grading. They also wanted to keep from acquiring land or easements, as it would be time-consuming and costly. This position heavily influenced our design. We determined the roundabout would need to be offset to the west.

The offset roundabout keeps the circular shape and provides deflection in and out of the roundabout to maintain consistent slow speed. The consistent and slower speed provides the safest and most efficient traffic flow through the intersection.

To streamline the intersection, we made changes to one of the driveways serving Casey’s gas station, along with a strip of shops. It originally had a driveway that was very close to 91st and Lexington. Our design team changed it to an exit only to keep traffic moving and improve safety. The additional entrances were left as is, giving patrons the option to enter or exit there.

To achieve the grades needed and minimize the impact to the railroad’s property, the sidewalk on the east side was redesigned. Instead of sloping toward the roadway, it was tipped away from it. The sidewalk drainage now flows to an existing ditch. This approach allowed us to tie the construction slopes back into the grades more quickly, while missing railroad properties.

The city asked our team to keep the roadway open throughout construction. While work was underway, a northbound vehicle could not make a left-hand turn without mounting the truck apron, which was off limits during paving. We decided to change the configuration. If someone was making a northbound left-turn during construction, they would have to take a detour using Commerce Drive northbound to access Lexington Avenue southbound and then make a right-turn.

To enhance the aesthetics of the roundabout, the landscape architect, Landworks Studios, created a sign and plantings for the area. Our team designed a water line to run to the center of the island, ending in a spigot. This allows the city to easily water the landscaping here.

With the new roundabout, traffic flows freely through the 91st and Lexington intersection. And, more importantly, safety has increased for area drivers of all ages.