Route P Intersection Improvements in St. Charles

PROJECT UPDATE JANUARY 24, 2025

After meeting with the public in October 2024 and careful consideration of the options to construct either a roundabout or a traffic signal at the Route P at Koch Road intersection in O’Fallon, MO, the Missouri Department of Transportation St. Louis District is moving forward with plans to add turn lanes and install a traffic signal at that location. 

During our October 8, 2024, public meeting, we gathered feedback provided by the attendees of the open house and via online submissions. The majority favored a signalized intersection, with approximately 30 percent of the feedback favoring a roundabout. Both options had acceptable traffic operations to reduce the delay at this intersection. MoDOT also explored a third option suggested by several meeting participants, which was to construct a Green T intersection, like one at Route 79 and T.R. Hughes Boulevard, or the Green T at Route K and the South Outer Road. However, the Green-T intersection had property access concerns that could not be resolved and was eliminated as a feasible alternative. The MoDOT team has initiated the next steps to meet the schedule of when project funding is available in fiscal year 2027 but an exact date of construction is not known currently. 

MoDOT wants to thank everyone who attended, and we appreciate the feedback that was given from the public meeting. 

What’s the problem?

According to a MoDOT five-year traffic study conducted from 2015-2020, 37 crashes occurred at the Route P and Koch Road intersection. Of those 37 crashes, 57% were rear end collisions and 8% of the crashes were left turn right-angle “T-bone” collisions.

Traffic on Koch Road has grown to the point that the Route P and Koch Road intersection warrants an improvement to provide safer, more efficient access in and out for motorists. The MoDOT traffic study concludes that either a roundabout or traffic signal being needed for the intersection. Residents and the city of O’Fallon have encouraged MoDOT to reduce the speed limit on the eastern portion of this highway.
 

What could the intersection look like?

Between the two options, MoDOT proposes construction of a roundabout at Koch Road. Roundabouts have been proven to virtually eliminate right-angle “T-bone” crashes that historically lead to fatalities and severe injuries. A roundabout can help with slowing traffic, while still maintaining better access from the side street. A 2001 Insurance Institute for Highway Safety (IIHS) study showed that roundabouts reduced crashes and injuries. The study showed a 38% reduction for all crash severities combined and 76% for all injury crashes. The reductions in the number of fatal and incapacitating injury crashes were estimated at about 90% compared to intersections with either a signal or stop sign. 

When will this be done?  

The project is currently funded via MoDOT Safety Funds* for construction in MoDOT’s fiscal year 2027 (begins 7/1/2026). Preliminary design is anticipated to begin in early 2025.

* Corrected to reflect funding source.  Earlier version of the website language attributed the funding to Congestion Mitigation and Air Quality (CMAQ) from the Federal Highway Administration for this project.