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FHWA Home / Safety / Intersection / Intersection Safety

Crossover-based Intersections

Outreach & Education
Technical Materials
Other Resources
State & Federal Research
National Partners

Motorists, pedestrians, and bicyclists face greater mobility challenges and safety risks at intersections as traffic volumes grow and congestion worsens. Agencies need safer, more balanced designs that keep people moving. Innovative intersection designs offer many safety and operational benefits, and are being built more often because they can deliver more for less.  In the case of Crossover-based intersection designs, some or all traffic crosses over to the left-hand side of the roadway in order to facilitate unopposed left turn movements. The two most common forms of innovative intersection designs that rely on crossovers are the Diverging Diamond Interchange (DDI) and the Displaced Left Turn intersection (DLT). The diagrams below illustrates these two designs – the DDI (on the left) and the DLT (on the right).

Diagram: Crossover Intersection Diagram: Crossover Intersection

The success of innovative intersection designs begins with reducing the number and severity of conflict points – locations where user paths coincide. Conflict points are categorized as crossing, merging (or joining) and diverging (or separating). The diagrams below illustrate the differences in conflict points between conventional designs and equivalent DDI and DLT designs. For the DDI, there are 14 conflict points (2 crossing, 6 merging and 6 diverging), compared to 26 conflict points (10 crossing, 8 merging and 8 diverging) for a conventional diamond design. For the DLT, there are 28 conflict points (12 crossing, 8 merging and 8 diverging), compared to 32 conflict points for a conventional intersection (16 crossing, 8 merging and 8 diverging). In both cases, total conflict points are reduced, and the conflicts that remain are lesser overall severity – mostly the same-direction types with less likelihood of severe injury.

Vehicle-Vehicle
Conflict Points
Conventional
Diamond Interchange
Diverging
Diamond Interchange
Diamgram Legend: Black = Crossing, Gray = Merging, White = Diverging Diagram: Diagram:
Crossing 10 2
Merging 8 6
Diverging 8 6
Total 26 14

 

Vehicle-Vehicle
Conflict Points
Conventional
Intersection
Displaced Left
Turn Intersection
Diamgram Legend: Black = Crossing, Gray = Merging, White = Diverging Diagram: Diagram:
Crossing 16 12
Merging 8 8
Diverging 8 8
Total 32 28

 

Outreach and Education

Because innovative intersections generally look or function differently from conventional designs, it is important for outreach and education to take place. These conversations begin by communicating the magnitude and importance of the intersection safety challenge. With roughly ¼ of all traffic fatalities in the United States associated with intersections, it is critical that safer designs are implemented as widely and routinely as possible. But safer designs must also keep people and goods moving. To help state and local road agencies advance innovative intersection designs, the FHWA produces materials intended to communicate their advantages and benefits to a variety of different audiences. These resources are conveniently listed and linked below:

  1. plus symbol Information Videos

    • Alternative Intersections: Diverging Diamond Interchange Informational Video [YouTube]
    • Alternative Intersections: Displaced Left Turn Intersection Informational Video [YouTube]
    • Video Case Study: Diverging Diamond Interchange – I-44 at State Route 13, Springfield MO [YouTube]
    • Video Case Study: Diverging Diamond Interchange – I-15 at Main Street, American Fork UT [YouTube]
    • Video Case Study: Diverging Diamond Interchange – I-15 at State Route 92/Timpanogos Hwy, Lehi UT [YouTube]
    • Video Case Study: Displaced Left Turn – State Route 30 at Summit Drive, Fenton MO [YouTube]
    • Video Case Study: Displaced Left Turn – Bangerter Highway Corridor, Salt Lake County UT [YouTube]
    • Video Case Study: Displaced Left Turn – Redwood Road at 6200 South, Taylorsville UT [YouTube]
  2. plus symbol Informational Brochures

    • Alternative Intersections: Diverging Diamond Interchange [HTML] [PDF]
    • Alternative Intersections: Displaced Left Turn Intersection [HTML] [PDF]
  3. plus symbol Informational Case Studies

    • Georgias First Restricted Crossing U-Turn Intersections [HTML] [PDF]
    • Case Study Fact Sheet: Diverging Diamond Interchange – I-44 at State Route 13, Springfield MO [HTML] [PDF]
    • Case Study Fact Sheet: Diverging Diamond Interchange – I-15 at Main Street, American Fork UT [HTML] [PDF]
    • Case Study Fact Sheet: Diverging Diamond Interchange – I-15 at State Route 92/Timpanogos Hwy, Lehi UT [HTML] [PDF]
    • Case Study Fact Sheet: Displaced Left Turn – State Route 30 at Summit Drive, Fenton MO [HTML] [PDF]
    • Case Study Fact Sheet: Displaced Left Turn – Bangerter Highway Corridor, Salt Lake County UT [HTML] [PDF]
    • Case Study Fact Sheet: Displaced Left Turn – Redwood Road at 6200 South, Taylorsville UT [HTML] [PDF]
  4. plus symbol Public Roads Magazine Articles

    • "Design at the Crossroads", Jul/Aug 2013, Vol. 77, No. 1 [HTML]
    • "The Double Crossover Diamond", Nov/Dec 2010, Vol. 74, No. 3 [HTML]
    • "A New Left Turn", Jul/Aug 2009, Vol. 73, No. 1 [HTML]

Technical Materials

Photo: Intersection

 
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Other Resources

  1. plus symbol State Highway Agency Resources:

    • Indiana DOT – Intersection Decision Guide (Indiana, 2014) [PDF]
    • Kentucky Transportation Cabinet/Kentucky Transportation Center
      • Congestion Toolbox: Diverging Diamond Information [HTML]
      • Displaced Left Turn Information [HTML]
      • Intersection Design Analysis Tool (IDAT) [HTML]
    • Maryland SHA – Applied Technology and Traffic Analysis Program Tools [HTML]
      • Unconventional Arterial Intersection Design Presentation [HTML] [PPT]
      • Unconventional Intersection Design Analysis (MUID) Tool [HTML]
    • Minnesota DOT – Diverging Diamond Information [HTML]
    • New York State DOT – Diverging Diamond Information [HTML]
    • Nevada DOT – General Information [HTML] – Driving the Moana Lane (Reno) DDI: Video Simulation [MOV]
    • Texas DOT/Texas Transportation Institute – Mobility Strategies (Texas, 2013) [HTML]
      • Innovative Intersections – Executive Summary [PDF] – Technical Information [PDF]
      • Continuous Flow Intersections – Technical Information [PDF]
      • Diverging Diamond Interchange – Executive Summary [PDF]
    • Utah DOT
      • CFI Guideline: Guide to Continuous Flow Intersections (Utah, 2013) [PDF]
      • DDI Guideline: Guide to Diverging Diamond Interchanges (Utah, 2014) [PDF]
      • UDOT Innovative Intersections and Interchanges Videos [YouTube]

State & Federal Research

National Partners

Page last modified on February 1, 2017
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