Highway 109 and Clayton Road: Why Southbound Drivers Are Stuck at the Light
Since MoDOT removed the flashing yellow left-turn arrow at Route 109 and Clayton Road, southbound drivers face multi-minute waits, and morning high school traffic backs up onto the highway.
Opinion. This piece reflects the views of a resident, not reporting or an official position.
If you drive south on Highway 109 and turn left onto Clayton Road in the morning, you already know the problem: you wait, and wait, and wait some more. A light that used to keep traffic moving now regularly holds southbound drivers for several minutes at a time, and the line of cars waiting to turn can stretch well back up the highway.
What changed
For years, drivers turning left from southbound Route 109 onto Clayton Road could turn on a yield. When there was a gap in oncoming traffic, you went. That permissive left turn, shown on most modern signals as a flashing yellow arrow, meant the turn lane cleared steadily even when the protected green arrow wasn’t lit.
The Missouri Department of Transportation (MoDOT), which controls the signal because Route 109 is a state highway, no longer allows that flashing yellow arrow at this intersection. Southbound left turns now have to wait for the protected green arrow. Every driver in the turn lane sits through the full signal cycle, even when there is no oncoming traffic at all.
Why mornings are the worst
The timing could hardly be worse. Lafayette High School sits on Clayton Road near the intersection, so the morning school rush funnels a large share of its traffic through this one left turn: students driving themselves, parents dropping off, and buses.
With turns limited to the green arrow, only a handful of cars clear each cycle. The rest of the queue:
- Backs out of the turn lane and into the through lanes of Highway 109, where drivers approaching at highway speed suddenly meet stopped traffic.
- Encourages risky decisions. Drivers late for first bell are tempted to run the end of the arrow, cut across lanes to get into the turn, or look for shortcuts through nearby neighborhoods.
- Adds up to hours of lost time. A few extra minutes per car, multiplied across hundreds of cars every school morning, is many hours of combined delay for Wildwood drivers each day.
Whatever the intent behind the change, it has created a daily safety problem of its own.
The flashing yellow arrow isn’t unusual
MoDOT itself has used flashing yellow arrows for permissive left turns on state routes since 2006, and its own driver guidance explains the rule plainly: on a flashing yellow arrow you may turn, but you must first yield to oncoming traffic and pedestrians. Intersections all over the St. Louis area still use them. If MoDOT has publicly explained why it removed the arrow at this intersection, we haven’t found it, and nothing has been done about the morning backups it created.
What you can do
If this intersection affects your commute, the most useful thing you can do is tell the people who can change it:
- Report it to MoDOT. Call MoDOT customer service at 1-888-ASK-MODOT (1-888-275-6636) or use the contact options at modot.org. Be specific: southbound Route 109 left turn onto Clayton Road, weekday mornings, and how long you waited.
- Contact your City Council member. The city doesn’t control state highway signals, but council members can press MoDOT on residents’ behalf. Find your council member here.
- Check conditions before you leave. The MoDOT Traveler Information Map shows work zones and incidents on state routes.
We’ll update this article if MoDOT changes the signal or explains its decision. If you’ve heard from MoDOT about this intersection, let us know.
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