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FHWA Home / Safety / Proven Safety Countermeasures / Reduced Left-Turn Conflict Intersections

Reduced Left-Turn Conflict Intersections

Reduced left-turn conflict intersections are geometric designs that alter how left-turn movements occur. These intersections simplify decision-making for drivers and minimize the potential for higher severity crash types, such as head-on and angle. Two highly effective designs that rely on U-turns to complete certain left-turn movements are known as the Restricted Crossing U-turn (RCUT) and the Median U-turn (MUT).

Restricted Crossing U-turn

The RCUT intersection, also known as a J-Turn, Superstreet, or Reduced Conflict Intersection, modifies the direct left-turn and through movements from cross-street approaches. Minor road traffic makes a right turn followed by a U-turn at a designated location—either signalized or unsignalized—to continue in the desired direction. The RCUT is suitable for and adaptable to a wide variety of circumstances, ranging from isolated rural, high-speed locations to urban and suburban high-volume, multimodal corridors. It is a competitive and less costly alternative to constructing an interchange. RCUTs work well when consistently used along a corridor, but also can be used effectively at individual intersections. Studies have shown that installing an RCUT can result in a 30-percent increase in throughput and a 40-percent reduction in network intersection travel time.1

Illustration: This illustration shows a four-lane divided highway intersected by a two-lane minor road. In this example of an unsignalized Reduced Conflict U-Turn intersection, traffic from the minor street must turn right. Cross street left turn and through traffic must make a U-turn downstream of the intersection. Traffic is permitted to take a left turn directly from the divided highway onto the minor road. All movements except for through movements on the arterial are stop-controlled.

Example of a unsignalized RCUT intersection. Source: FHWA

Median U-turn

The MUT intersection modifies direct left turns from the major approaches. Vehicles proceed through the main intersection, make a U-turn a short distance downstream, followed by a right turn at the main intersection. The U-turns can also be used for modifying the cross-street left turns, similar to the RCUT.

Illustration: This illustration shows a four-lane divided highway intersected by a two-lane minor road. In this example of a Median U-turn intersection, traffic from the minor street is permitted to proceed through the intersection or turn right. Left turn traffic from the minor street must turn right and make a U-turn at a U-turn bulb downstream of the intersection. In this intersection, traffic on the arterial is permitted to proceed through the intersection or turn right. Since left turns are not permitted, left turn traffic from the arterial must proceed downstream of the intersection, make a U-turn, and turn right onto the minor road.

Example of a MUT intersection. Source: FHWA

The MUT is an excellent choice for intersections with heavy through traffic and moderate left-turn volumes. Studies have shown a 20- to 50-percent improvement in intersection throughput for various lane configurations as a result of implementing the MUT design. When implemented at multiple intersections along a corridor, the efficient two-phase signal operation of the MUT can reduce delay, improve travel times, and create more crossing opportunities for pedestrians and bicyclists.

Sources

1. Hugher and Jagannathan. Restricted Crossing U-Turn Intersection. FHWA-HRT-09-059, (2009).

2. Edara et al. Evaluation of J-turn Intersection Design Performance in Missouri. MoDOT, (2013).

3. Hummer and Rao. Safety Evaluation of a Signalized Restricted Crossing U-Turn. FHWA-HRT-17-082, (2017).

4. Hummer et al. Superstreet Benefits and Capacities. FHWA/NC/2009-06, NC State University, (2010).

5. Synthesis of the Median U-Turn Treatment, Safety, and Operational Benefits, FHWA-HRT-07-033, (2007).

Safety Benefits:

RCUT

Two-Way Stop-Controlled
to RCUT:

54%

reduction in fatal and injury crashes.2

Signalized Intersection
to Signalized RCUT:

22%

reduction in fatal and injury crashes.3

Unsignalized Intersection
to Unsignalized RCUT:

63%

reduction in fatal and injury crashes.4

MUT

30%

reduction in intersection-related injury crash rate.5

 


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Page last modified on October 28, 2021
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