Solutions You Might See in 2023
We encourage innovative solutions to our transportation challenges. These are just some options that we traditionally consider. Click or hover over each image to learn more!
Two-Way Outer Roads
Two-way outer roads are what is currently in the area. The roads have existed like this for decades and there is an ease of access and clear comfort level drivers have with two-way outer roads.
Works best for:
- Addressing localized access
- Reducing travel distance
- Ease in doubling back or turning around
Tradeoffs:
- More intersections in interchanges
- Less efficient interchanges
- More expensive to reduce congestion
One-Way Outer Roads
One-way outer roads would remove the two ramp intersections and allow drivers to exit and enter the interstate independent of the interchange, usually without a signal. This makes the crossroad and interchange function more efficiently.
Works best for:
- Reducing travel time in congested area
- Putting more traffic on the outer roads near the businesses
- Improving safety by creating intersections with fewer conflict points
Tradeoffs:
- Increases travel distance between two points
- Potential for increased speeds
- Unpopular to the public
Single-Point Urban Interchange (SPUI)
These interchanges allow two opposing left turns at the same time. This generally lets large volumes of traffic clear out of a limited space, safely and efficiently.
Works best for:
- Tighter areas since they take up less space
- Reducing signals to improve traffic flow
- Accommodating large trucks
Tradeoffs:
- Are more costly to build due to wide bridge structure
- More difficult for pedestrians to cross
- Longer time sitting at signal due to large volumes of traffic that clears out each time
Diverging Diamond Interchanges (DDI)
DDIs increase capacity by removing the need for a left turn signal which gives through traffic more green light time.
Works best for:
- Moving a high volume of traffic through an intersection
- Simplifying signal timing at intersections with high volume of left turn traffic
- Increasing sight distance when turning
Tradeoffs:
- Unfamiliar configuration of DDI including moving to left side of road
- Difficult for pedestrians to cross
- Less efficient for through traffic
Roundabouts
Roundabouts let a lot of traffic through one location without signals or long wait times.
Works best for:
- Moving traffic efficiently without signals
- Slowing vehicles and improving safety
- Reducing crash severity by lessening the angle of crashes
Tradeoffs:
- Driver uncertainty can result in failure to yield or trying to cut the roundabout
- Need to be in flat area with good sight distance
- Smaller roundabouts can be difficult for large trucks to navigate
General Concepts
The videos below include interchange layouts with one-way and two-way outer road design options. Please understand that these are not final designs, but are ideas to help MoDOT guide teams during the development process.