Significant changes are on the horizon for Shawnee Mission Parkway over Interstate 35 in Merriam.
Earlier this month, the Merriam City Council voted 7-0 to accept recommendations from a study to change Shawnee Mission Parkway over I-35 into a diverging diamond. Councilmember Whitney Yadrich was absent.
This $32.1 million project will build the same type of interchange traffic pattern that drivers use at 95th Street over I-35.
Here’s a look at the proposed changes — and what engineers at Overland Park-based HNTB say could happen if no changes were made. HNTB is the same firm that is working on solutions to flooding in downtown Merriam, with early options proposing razing all of historic downtown.
Current issues to increase without project, engineers say
Brent Gerard, a project manager with HNTB, shared the following traffic results with the city council on Feb. 9:
- The heaviest congestion on Shawnee Mission Parkway, in the study area, is between southbound I-35 ramps and Antioch Road.
- The worst movement, caused by poor lane usage, is westbound on Shawnee Mission Parkway east of Antioch Road (just before the intersection).
- While both morning and evening rush hours are poor, the afternoon is worse.
Additionally, northbound and southbound I-35 lanes are either nearing or over capacity within the study area (between Johnson Drive and 67th Street to the north and south).
Without any changes to the interchange, congestion is predicted to increase on Shawnee Mission Parkway east of I-35 — at Ikea Way, Slater Street, Antioch Road and Craig Drive.
In the afternoon, both northbound and southbound I-35 traffic congestion is over capacity without any changes.
Gerard said that in the worst case scenarios, Shawnee Mission Parkway vehicle queues are predicted to back up all the way to Metcalf Avenue without any changes.
“In those worst case scenarios, this (vehicle queues east of Antioch Road) backs up almost to Metcalf, which is not great,” Gerard said.
The project calls for diverging diamond, Antioch changes
After completing the study, HNTB found that the best solution for the traffic congestion on Shawnee Mission Parkway at I-35 is a diverging diamond interchange.
Gerard said diverging diamond interchanges help alleviate traffic congestion by cutting out one of the traffic signals drivers need to wait through.
“By putting traffic on the opposite side of the road, that left takes a left at the same time they’re going through,” Gerard said. “So now, you don’t need two phases for that.”
This is similar to the interchange at 95th Street over I-35, but there is one key difference: Two left lanes from Shawnee Mission Parkway will be dedicated to the on-ramps for I-35, requiring any driver trying to turn right onto that same ramp to stop and wait for the left-turning traffic.
The diverging diamond interchange is predicted to result in much less vehicle queuing east of I-35 on Shawnee Mission Parkway, Gerard said.
Pedestrians will also be able to walk along the center of the diverging diamond, according to HNTB’s plans.
In addition to the diverging diamond interchange, which would start at roughly Ikea Way and southbound I-35 ramps, HNTB is proposing changes east of the Antioch Road and Shawnee Mission Parkway intersection.
HNTB is proposing closing the Shawnee Mission Parkway median breaks at Hadley Street and, as a result, extend the left-turn lane and the outside through-lane by hundreds of feet to the east.
This is an additional $4.3 million, but without these changes, Gerard said the diverging diamond interchange will be less effective.
Watch the city council’s entire discussion in the embedded video below, starting at 55:42.
Merriam needs federal funding for the $32.1M project
- Public Works Director Celia Kumke told the city council on Feb. 9 that the city has no plans to complete this project without federal funding.
- “As we all know, (the Kansas Department of Transportation) has so many needs and priorities, so completing this concept study is the first step toward showing KDOT that the interchange improvements are a priority for the city and that we are willing to spend city funds upfront to develop a solution to advance this project,” Kumke said.
- The study helps the project score higher for federal funding opportunities as well, Kumke added.
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