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
    InterchangeLocationDDI Cost (real or estimated)Alternative Design CostCost Savings
    I-44 / Route 13Springfield, MO$3.2 MillionOver $10 Millionabout 70%
    I-435 / Front StreetKansas City, MO$6.7 Million

    Diamond $11.4 Million

    Single Point Urban Interchange  (SPUI) $25 Million

    about 75%
    SR-265 / SR-62Utica, IN $52 Million$118 Million$66 Million
    I-590 / Winton RoadBrighton, NY$3-$4 Million

    SPUI $10 Million

    Triple Left Diamond $13.6 Million

    about 75%
    • 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

  • For further details on the benefits of the DDI, see our list of courses.