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Development of Design Guidelines for J-Turn Intersections

Description:

In a typical J-Turn intersection, also known as a Restricted Crossing U-Turn (RCUT) intersection, vehicles turning left from the minor road onto the highway must first turn right and then make a U-turn to complete the maneuver. The American Association of State Highway and Transportation Officials (AASHTO) Green Book contains guidelines for some of the components that are typically used in a J-Turn intersection such as auxiliary lanes but does not present guidance for the design of these components in the context of a J-Turn intersection. The interaction between design elements such as acceleration and deceleration lane lengths, median width, pavement markings, and signage is an important consideration in the development of an effective J-Turn intersection design. In addition, there is a need for effective pavement markings and signage because many drivers are not familiar with the proper way to navigate J-Turn intersections. In order to promote the implementation of J-Turn intersections and enhance their performance, there is a need for a comprehensive set of design guidelines that take into consideration the unique characteristics and interactions of design elements at J-Turn intersections and for recommendations regarding conditions under which implementation of a J-Turn intersection could be beneficial.

Objective:

The objective of this research is to produce a set of proposed guidelines to aid practitioners in the design of J-Turn intersections.

Benefits:

Previous studies have demonstrated the benefits of J-Turn intersections. The development of design guidelines for J-Turn intersections would further enhance these benefits by promoting standard practices that improve their performance and by providing recommendations regarding conditions for their use. Since some agencies may currently be reluctant to implement J-Turn intersections due to a lack of design guidance, the development of such guidance would facilitate more widespread implementation of J-Turn intersections. In addition, development of guidance for signage and striping at J-Turn intersections could help to reduce confusion for drivers who are not familiar with the proper way to navigate through a J-Turn intersection and could lead to greater public acceptance of this innovative design.

Related Research:

Several studies in states such as Missouri1 and North Carolina2 have investigated the operational and safety performance of J-Turn intersections. These studies have utilized measures such as travel times, acceleration lane usage, traffic conflicts, and crashes to evaluate the performance of J-Turn intersections and compare them to conventional two-way stop controlled (TWSC) intersections. Although these studies have demonstrated the benefits of J-Turn intersections, they have not looked at the development of design guidance for these innovative intersections.

The AASHTO Green Book provides design guidance for some of the components of J-Turn intersections. For example, guidelines for auxiliary lane width and deceleration lane width are included in Chapter 9 of the Green Book which pertains to intersections. Design recommendations for acceleration lane lengths are presented in Chapter 10 on interchanges. The guidelines for these components in the Green Book are not presented in the context of J-Turn intersections.

Some additional information for J-Turn intersections is provided in other resources as well. The Alternative Intersections And Interchanges Informational Report from FHWA in 2009 includes guidance regarding the crossover spacing for J-turns. NCHRP Report 650 includes case studies for J-Turn intersections and other rural expressway intersection safety treatments along with recommendations for future research. The report recommends that design guidance for J-Turn intersections should be included in future updates of the AASHTO Green Book. The report also indicates that many state transportation agencies are not implementing J-Turn intersections because of the lack of design guidance.

1 Edara, P., Sun, C. and Breslow, S. (2014). Evaluation of J-turn Intersection Design Performance in Missouri, Final Report, MoDOT, Project: TRyy1304. Available at http://library.modot.mo.gov/RDT/reports/TRyy1304/cmr14-005.pdf.

2 Hummer, J.E., Haley, R.L., Ott, S.E., Foyle, R.S., and Cunningham, C.M. (2010). Superstreet Benefits and Capacities, Final Report, NCDOT, Project: 2009-06.

Sponsoring Committee:AKD10, Performance Effects on Geometric Design
Research Period:12 - 24 months
RNS Developer:Henry Brown, Praveen Edara, Carlos Sun, Larry F. Sutherland
Source Info:Problem statement developed as a result of the Safety Effects of Geometric Design Decisions Workshop at the 2013 mid-year meeting of TRB Committees AFB10 (Geometric Design) and AHB65 (Operational Effects of Geometrics), in conjunction with the AASHTO Technical Committee on Geometric Design.
Date Posted:07/07/2014
Date Modified:07/15/2014
Index Terms:Intersections, Highway design, Guidelines, AASHTO Green Book, Turning traffic, Road markings, Traffic safety,
Cosponsoring Committees: 
Subjects    
Highways
Design
Operations and Traffic Management
Safety and Human Factors

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