standard-title Benefits


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
Supporting Data
  • MODOT survey shows that 97% of drivers feel safer in the new Springfield DDI compared to the previous diamond interchange
  • Crash data for the new Springfield DDI show a 60% reduction in collisions in a five-month comparison of the old interchange
  • Versailles, France DDI showed that within a five-year time span that was examined, there were only been 11 reported light crashes

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
Supporting Data
  • MODOT survey shows that 95% of drivers felt that there was less congestion in the new Springfield DDI compared to the previous diamond interchange
  • Daily traffic backups that sometimes had over a mile queue were completed eliminated once the construction of the new Springfield DDI was complete.

Cost Benefits

For a retrofit
  • Existing bridge can usually be used
  • Additional right-of-way rarely needed
  • Construction time is reduced
  • Maintenance of traffic is simplified during construction
For a new interchange
  • Fewer lanes than other interchange forms
  • Less bridge structure
  • Less right-of-way than a cloverleaf form
Interchange Location DDI Cost (real or estimated) Alternative Design Cost Cost Savings
I-44 / Route 13 Springfield, MO $3.2 Million Over $10 Million about 70%
I-435 / Front Street Kansas City, MO $6.7 Million Diamond $11.4 Million
Single Point Urban Interchange (SPUI) $25 Million
about 75%
SR-265 / SR-62 Utica, IN $52 Million $118 Million $66 Million
I-590 / Winton Road Brighton, NY $3-$4 Million SPUI $10 Million
Triple Left Diamond $13.6 Million
about 75%