Interchanges are designed to fit specific local conditions and meet driver expectations. Factors such as safety, cost, capacity, environment, development and politics can vary at every site; consequently there are hundreds of unique, one-of-a-kind interchanges worldwide. Below are some of the more common interchanges you will find on Missouri roadways.
Some basic types of interchanges are: diamond, directional and cloverleaf.
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Diamond interchanges are the most common type and are suitable in both rural and urban areas. They can become congested, though, by a high volume of left-turning movements on the crossroad, and they often include signals that control ramp access to and from the crossroad. Spacing between the ramps is critical for efficient movement of traffic through the interchange.
- Diverging diamond interchanges (DDI) are diamond interchanges that more efficiently handle heavy left-turn movements. While the ramp configuration is similar to a traditional diamond interchange, traffic on the crossroad moves to the left side of the roadway for the segment between signalized ramp intersections. The nation’s first DDI was built by MoDOT in Springfield in 2009.
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Directional interchanges accommodate high-volume turning movements where two freeways intersect. Direct ramp movements reduce travel distance, increase speed and capacity, eliminate weaving and avoid the need for “out-of-direction” travel on a loop. These interchanges are costly to construct due to the increased number and length of ramps and the number of bridge crossings.
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Cloverleaf interchanges can be used where two high volume freeways intersect. Loop-ramps are used to accommodate left-turning movements. However, this configuration provides short weaving areas for traffic entering or leaving the interchange. A cloverleaf interchange occupies a relatively large area of right of way.