January 27

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What are Restricted Crossing U-Turn Intersections?

By Mike Spack

January 27, 2015

Design, Intersection, RCUT, Restricted Crossing U-Turn

A Restricted Crossing U-Turn, or RCUT, intersection is an intersection design that restricts left turns at an intersection, but allows the same movement downstream via a u-turn.

The RCUT falls under a group of strategies often referred to as conflict point management. The goal of an RCUT is to restrict or relocate certain movements to improve a roads overall safety and reduce delays. RCUTs can go by several different names depending upon your location, and include Superstreet Intersection, and J-Turn.

The basic RCUT restricts the incoming and outgoing side streets to right turn movements only. Vehicles that want to turn left, or cross to the opposite side street, must do so indirectly by first turning right onto the mainline, weaving across to the left most lane to complete a U-turn, and then traveling back to the intersection in question to complete their desired movement. Another form of RCUT also relocates the mainline left turns, directing those movements beyond the intersection to the U-turn location.

Pedestrian movements around an RCUT remain the same on the side streets, but vary in form on the mainline crossing depending upon the circumstances. In some cases, only one path across the mainline is provided diagonally, for example from the northeast quadrant to the southwest quadrant. This route directs pedestrians to cross to the center island separating the mainline left turn lanes and then to continue across to the opposite corner. While this path reduces pedestrian-vehicle conflicts, it also increases the overall distance traveled, and can result in pedestrians having to cross both side streets. Enforcing this type of crossing also requires landscaping, or other fixtures, to prevent illegal crossings.

RCUT Intersection

[Download the guide: Restricted Crossing U-Turn Intersection]

Benefits

  • Reduction in vehicle conflict points from the 42 found in a traditional intersection to either 18, or 24, depending upon whether mainline left turn movements have been restricted, or not.
  • Approximately 30% reduction in the crash rate, and up to a 50% reduction in crash severity
  • Increased capacity and reduced delays in certain cases. Such as with roads that have high mainline left turn volumes
  • Lower construction costs compared to an interchange, or a new traffic signal with added turn lanes on the side streets
  • Shorter construction time compared to an interchange

Limitations

  • Increased distance and travel time for left turn and through movements from the side streets
  • Non-traditional pedestrian route can be confusing, especially the visually impaired
  • There are no established guidelines, or warrants, to assist in justifying an RCUT
  • Design guidance and standards are still evolving, and could change over time
  • Potential for increased right-of-way, room, needed compared to a traditional intersection
  • Increased signing and striping requirements to provide clear and timely information for drivers at, what amounts to be, three separate intersections
  • Public acceptance of RCUTs varies greatly

Design Guidance

  • An intersection comparison should be completed evaluating an RCUT against a traditional intersection in terms of at least safety, operations, and pedestrian traffic
  • Median widths of 47 to 71 feet may be needed depending upon the design of the vehicle expected to make the U-turn. Semi-trucks, for example, will require a larger turning radius
  • 800 feet of separation, or more, between the intersection and the U-turn locations. This distance should reflect a balance between the vehicle’s need to change lanes, U-turn turn lane storage space needed, and appropriate spacing for approach signing and striping
  • Islands and medians are needed to reinforce the movement restrictions, both vehicular and pedestrian
  • Acceleration lanes for the U-turn may be necessary to allow safe merging into mainline traffic
  • Traffic signals can be used if warranted and would require fewer phases since, at minimum, the side street movements have been restricted to right turns only
  • Overhead signing has not been shown to be necessary based on available data. However, increased signing and striping is necessary to clearly direct motorists through the intersection
  • Pedestrians may need additional way finding signs, and other landscaping treatments, to properly direct them along the desired path
  • An alternative path for bicyclists may be needed for those who are not comfortable riding in mainline traffic, or who do not want to travel the extra distance to use the U-turn

[Download the guide: Restricted Crossing U-Turn Intersection]

Links

  • While there are no formal warrants for RCUTs, FHWA has produced CAP-X, a planning level tool to help determine which, if any, alternative intersections or interchanges may be suitable. https://www.fhwa.dot.gov/software/research/operations/cap-x/

    Additionally, NCDOT just completed a research project which provides guidelines on signalization needs at RCUTs. These guidelines can be used for any RCUT or RCUT type element (e.g. a left-over on a divided median) and are intended to help provide guidance when you are considering peak-hour needs at intersections with fewer than four legs.
    https://connect.ncdot.gov/projects/research/Pages/ProjDetails.aspx?ProjectID=2017-11

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    Mike Spack

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