Displaced Left Turn

Submitted by: St. Louis District 

Innovation Description and Benefit:

The new Displaced Left Turn Ramp at the MO 141/364 Interchange is an innovation that should benefit the travelling public by reducing the amount of time traffic needs to stop at the traffic signals at the interchange.  The off-ramp to Route 141 from EB MO 364 will no longer require a signal for that movement at the southside of the interchange.  Right turns will be free flow from this ramp to SB Route 141 while left turns to NB Route 141 will make that turning movement on the north side of the interchange.

This will allow left turns to occur simultaneously for both the WB and EB off-ramps from MO 364. Vehicle travel time is expected to be reduced by 70% for the NB 141 to WB 364 movement at the intersection. This ramp should improve safety by reducing the number of conflict points by eliminating the left turn signal phase at the south side of the interchange and by reducing the angle of incidents that occur at the revised north side intersection. In addition, the proposed improvements will reduce congestion on NB 141, reducing the number of rear-end crashes that occur during peak periods.  The cost of the short-term projects at the interchange was $4M. These projects provide both operational and safety benefits at the interchange until long-term improvements can be funded. The long-term improvements at the interchange will require further environmental study and would require significant funding.  

For More Information Contact

St. Louis District – Design

Dan Savageau at dan.savageau@modot.mo.gov or 314-453-5089.