Right-in/right-out

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The phrases Right-in/right-out (RIRO) or left-in/left-out (LILO) refer to a type of roadway intersection where in the minor street approach's ingress and egress are both restricted. The restrictions employed are just as the name implies: a RIRO prohibits vehicles from entering the intersection via any movement other than a right-turn; and a LILO only permits a left-turn entry. To exit, RIRO prohibits through or left-turns out; and LILOs only allow for left-turns.

The restrictions are typically enforced through geometric provisions such as a concrete island to direct vehicles into the right or left turns, as applicable; and to restrict vehicles from traveling through the intersection. The major roadway itself often has a median separating the two directions of mainline traffic. In situations where a median is not present along the mainline, RIRO and LILO configurations have been found to result in significant violation rates -- despite the geometric indications of the concrete island or any regulatory signing.

Typically, the use of a RIRO is prevalent in areas where vehicles drive on the right side of the roadway, and similarly LILO is most prevalent in areas where vehicles keep left. This is a result of how access points to minor streets are often on the outside of a roadway. However, both RIRO and LILO intersections exist along right-hand drive and left-hand drive roadways, particularly along bifurcated one-way roadways.

RIRO and LILO configurations generally improve the safety and efficiency of an intersection by reducing the number of conflict points between vehicles. However, motorists whom wish ingress or egress a RIRO or LILO via a restricted maneuver must often use alternate locations to perform a U-turn maneuver so that they may travel in their intended direction. As a result, RIRO and LILO configurations may improve the safety and operations of an intersection while consequently worsening those very concerns at another intersection upstream or downstream.

[edit] Examples

• In Canada, Highway 115 and parts of Highway 11 between Bracebridge and Huntsville in Ontario have RIRO access in various sections. There are no breaks in the median, and to turn around one must exit the highway at an interchange or special turn-around ramp and re-enter the highway in the opposite direction. (The RIRO sections on Highway 11 are expected to be upgraded to a full freeway in the future.)
• In the United States:
  • Many roads in New Jersey, including parts of U.S. Route 9 and Route 17, have RIRO access.
  • Ocean Parkway on Long Island in New York is primarily a RIRO-access road.
  • U.S. Route 90 Alternate (South Main) in Houston, Texas has property access on one side of the median, but all crossings are grade separated, with access to the roadway provided only by interchanges.
• The Bend Parkway north of the Powers Road intersection, has RIRO access.
• The first exit on the Delaware Route 1 Turnpike between Dover and Wilmington is a RIRO dedicated for commercial traffic accessing the Dover Air Force Base. Southbound commercial traffic wishing to access Dover A.F.B. must make a U-Turn in Little Heaven, seven miles south of the RIRO exit.
• In Hong Kong
  • Much of the portion of Route 1 between the Cross-Harbour Tunnel and the Lion Rock Tunnel.
  • Tuen Mun Road through the central part of Tuen Mun New Town
  • Connaught Road on Hong Kong Island.
  • Portions of Prince Edward Road between Mong Kok and the old Kai Tak Airport