The interchange for I-70 and U.S. 77, with a diverging diamond interchange. |
The project was let earlier this spring and construction begins this summer. How traffic passes through the DDI is unconventional, but easily understood by drivers unfamiliar with the design. This location was chosen because of it's importance to freight movement for trucks.
The DDI has many advantages over a traditional Diamond Interchange when
dealing with high traffic volumes and a high percentage of tractor-trailers by
reducing the number of conflict points. The benefits are listed below.
Safety Benefits
- Fewer conflict points (14 for DDI, 26 for
conventional)
- Conflict points spread out throughout interchange
- Better sight distance at turns
- Virtually no driver confusion (FHWA study and new DDI
observations in Springfield, MO)
- Traffic calming features when desired
- Wrong way entry to ramps extremely difficult
- Pedestrian crossings are shorter
Operational Benefits
- Unique phase combinations
- “Free” or simple left and right turns from all
directions
- Increases left turn lane capacity without needing more
lanes
- Only two phases needed, shorter cycle length
- Lanes with multiple assignments in all directions
- Better storage between the ramp terminals
- More functional during a power outage
- U-turns from highway are accommodated well
- Better signal network synchronization
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