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Public Works

I-70 Interchange at Highway K/Main Street Project

 

On March 2, 2011, the City of O'Fallon hosted an Open House meeting at City Hall to present four options for the reconstruction of the I-70 interchange at Highway K. Below is summary of the four options, as well as conceptual maps and simulations.

 

Option 11

This option features a grade-separated overpass along West Terra where it crosses Main Street, with “jug handle” side connections back to Main Street. West Terra from east to west now becomes an unrestricted through movement with no traffic signals. The “jug handle” connections to Main Street become right-in/out only connections along the east and west side, also eliminating the need for a signal. Reconstruction of some neighboring parking lots would be required. The westbound I-70 off-ramp is widened to become a triple left turn. This will require one additional lane under the I-70 bridge for southbound traffic. The interchange remains mostly the same, however by eliminating the signal at West Terra, traffic will flow better through the corridor.

 

Option 14

Everything on Option 11 above concerning West Terra is also implemented on this option. The difference is that the interchange configuration becomes a Diverging Diamond Interchange (DDI) instead of the traditional Diamond configuration that is there today. This DDI will require traffic to cross over and drive along the opposite side of the road for a short time under the I-70 bride, and then cross back to normal. This allows for traffic to enter and exist the ramps without having to cross oncoming traffic first. This option becomes the most efficient of the four presented. Unlike option 11, modifications to the southbound lanes under the I-70 bridge would not be required as part of the conceptual results.

 

Option 21

This option includes two roundabouts along West Terra east and west of Main Street. The intention of these roundabouts is to eliminate a left turn from West Terra onto Main Street, by requiring a driver to travel through the intersection, make a U-turn within the roundabout, and turn right back at the intersection at Main Street. Left turns from Main Street onto West Terra would still be allowed. Additionally, the northern ramps would be shifted south, closer to the I-70 bridge. This becomes a “tight diamond” configuration, which will provide some separation between West Terra and the ramps. The westbound I-70 off-ramp is widened to become a triple left turn. This will require one additional lane under the I-70 bridge for southbound traffic.

 

Option 22

This option converts West Terra to a one-way outer road, westbound only, from Sonderen to Woodlawn Ave. The I-70 motorists would exit and slip onto the outer road, and a motorist would slip off the outer road to get back on I-70 as well. The few businesses west of Main Street would share a short road connection to the one-way outer road. Most of the interchange configuration would be similar to what is proposed on option 11. One advantage is that there will only be one traffic signal  for both the ramp traffic and the West Terra traffic. The westbound I-70 off-ramp is widened to become a triple left turn. This will require one additional lane under the I-70 bridge for southbound traffic.

 

Miscellaneous

As mentioned at the meeting, intersection improvements to the intersection at Veteran’s Memorial Parkway and Highway K will also need to be completed to minimize bottlenecks in the corridor. The costs that were discussed would include improvements to that intersection as well.

 

The Conceptual Study report will be finalized within the next few weeks after compiling the results from the open house meeting.  Following completion of the report, the City will seek out funding opportunities to cover design, right-of-way acquisition, and construction. It is anticipated that this project would be finished (construction) in the 5-10 year time frame.

 

The four options are shown below in PDF format. These can be downloaded and printed at your computer for reference. Please click on the option number to view/download.

 

 
Option 11 (PDF)   Option 14 (PDF)
     
 
Option 21 (PDF)   Option 22 (PDF)

 

During the open house, a computer demonstrated an animation of traffic flowing through Option 14. This animation is available below. Additionally, another computer was showing some information on a looped presentation. That presentation is also available for download below.

 

AVI Animation (105 MB) Warning: LARGE SIZE
 
PowerPoint Presentation (18.5 MB)
Low-Quality version (5.5 MB)

 

Other resources

CONTACT: Jeff Schuepfer, Project Manager

E-MAIL: jschuepfer@ofallon.mo.us

PHONE: 636-379-5491