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Publication Number: FHWA-HRT-12-037
Date: June 2012

 

Field Evaluation of A Restricted Crossing U-Turn Intersection

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FHWA Publication No: FHWA-HRT-12-037

FHWA Contacts: Joe Bared, HRDO-20, (202) 493-3314, joe.bared@dot.gov, Brian Philips, HRDS-30, (202) 493-3468, brian.philips@dot.gov, and Wei Zhang, HRDS-10, (202) 493-3317, wei.zhang@dot.gov.

This document is a technical summary of the Federal Highway Administration (FHWA) report, Field Evaluation of a Restricted Crossing U-Turn Intersection (FHWA-HRT-11-067).

OBJECTIVE

This TechBrief describes comparisons of field observations of the operations of an unsignalized restricted crossing U-turn (RCUT) intersection in Maryland with a roughly comparable conventional stop-controlled intersection on the same corridor. It also summarizes the results of several crash analysis approaches for intersections converted from conventional designs to RCUT designs along two four-lane divided highway corridors in Maryland.

INTRODUCTION

An RCUT intersection is a promising treatment used to mitigate right-angle crashes where two-lane minor roads intersect with rural four-lane divided highways.

The RCUT design allows left turns from the highway onto intersecting minor roads, but it restricts turns from the minor road. Drivers desiring to make left or through movements from the minor road must first turn right and then make a U-turn to continue their desired movement. Figure 1 shows the RCUT intersection observed in this study.

This photo shows a satellite view of the restricted crossing U-turn (RCUT) intersection that was the subject of this study. A four-lane highway, US-15, is shown extending from the bottom left to the top right. A two-lane rural road, US-15 Business, intersects the highway in the north-south direction. The main intersection has an opening that allows traffic on the divided highway to turn left onto the local road. Curbing can be seen that blocks traffic from the minor road from turning left through the opening at the main intersection. Local road traffic must turn right at the main intersection. Directional U-turn openings can be seen in the highway median 1,800 ft on either side of the main intersection. These openings allow local road traffic to make a U-turn to complete through or left-turn movements.
Source: Google®, U.S. Geological Survey, Data SIO, NOAA, U.S. Navy, NGA, GEBCO.

Figure 1. Photo. RCUT intersection observed in this study.

RESEARCH

One objective of the RCUT study was to observe an operational RCUT intersection on a rural four-lane divided highway to evaluate its safety and operations from a human factors perspective. The observations were intended to support design guidance for future RCUT designs. To provide perspective on the RCUT intersection, observations were also made at a nearby conventional intersection on the same corridor.

The observations focused on the following:

A second objective was to perform a crash analysis to examine the effects of conversions from conventional intersections to RCUTs on two rural high-speed divided highway corridors in Maryland. This analysis focused on nine RCUT intersections that were deployed in Maryland between 1988 and 2003. Six of these intersections were deployed on US-15 in Western Maryland, and three were deployed on US-301 on the Delmarva Peninsula in Eastern Maryland.

Observational data were collected by scoring video collected at two Maryland intersections: an RCUT intersection and a nearby conventional intersection on the same highway—US-15 in Frederick County. At the RCUT, recordings were made on two weekdays. Six digital cameras, three on each of two masts, were used to record operations.

The RCUT intersections selected for the crash analysis are listed in table 1. The table also shows the log mile location of the intersection, the date the RCUT conversion was completed, and the nature of the U-turn crossings that were provided for left and through movements from the minor road. U-turn locations are labeled as dedicated directional U-turns (DDUTs) if they were channelized to permit U-turns originating from the direction of the main intersection. If the U-turns were made at a conventional intersection at the deployment date, then the U turn location is labeled "Inter." If drivers making through or left movements needed to use another RCUT intersection to make the U-turn, then the RCUT label is used.

Before-and-after comparisons of traffic crashes were made for each RCUT intersection, the sections of road between the RCUT intersection and the U-turn locations, and the U-turn locations. The approach is intended to capture the total impact of the RCUT treatment on crash probability.

Table 1. Maryland RCUT intersections.

Intersection

Log Milea

Deployment Date

Number of Approaches

Southern
U-Turn Location (Log Mile)

Northern
U-Turn Location (Log Mile)

US-15 at Hayward Road

16.180

9/1988

4b

DDUT at 15.829

Inter at 16.530

US-15 at Willow Road

17.070

11/1992

4

Inter at 16.530

Inter at 18.020

US-15 at Biggs Road

18.020

11/1992

4

RCUT at 17.070

RCUT at 18.330

US-15 at Sundays Lane

18.330

11/1992

4

RCUT at 18.020

RCUT at 18.870

US-15 at College Avenue

34.210

8/1994

4

DDUT at 33.823

DDUT at 34.619

US-15 at US 15 Business

35.020

9/1988

4

DDUT at 34.619

DDUT at 35.477

US-301 at Main Street

12.380

1/2003

4

U-turn

Inter at 12.880

US-301 at Del Rhodes Avenue

12.880

1/2003

4

Inter at 12.380

DDUT at 13.146

US-301 at Galena Road

43.670

1/2002

4

DDUT at 43.360

DDUT at 43.905

a The log miles are from Maryland State Highway Authority crash records except where offsets were added at county boundaries to adjust for changes in the way log miles were recorded by various agencies.
b This intersection has since been converted from a four-way to a three-way intersection.

RESULTS AND CONCLUSIONS

Based on the number of turning movements from the minor road, there were proportionally fewer traffic conflicts at the RCUT intersection. In particular, the RCUT intersection eliminated conflicts between vehicles turning left off of the highway and vehicles from the minor road turning left onto the highway. Additionally, the RCUT design appeared to have little or no effect on induced weaving movements on the highway.

Although acceleration lanes are not an intrinsic part of the RCUT design, they were part of the design at the RCUT observed in this study. Drivers who made left or through movements from the minor road appeared to make effective use of them.

Three approaches were used to estimate the affects of an RCUT conversion on crashes, and they all led to the same conclusion: the RCUT design reduces crashes. A simple 3-year before-and-after analysis suggested a 30 percent decrease in the average number of crashes per year. An analysis that adjusted the observed crash rate at RCUT locations for the observed crash rate at nearby conventional intersections on the same corridors suggested a 28 percent decrease in the average annual number of crashes. An Empirical Bayes analysis that adjusts for the expected number of crashes at similar intersections and average annual traffic suggested a 44 percent decrease in crashes.

Not only did the expected number of crashes decrease between 28 and 44 percent, but the crash data also suggest that the overall severity of crashes that occurred was lower with the RCUT design than a conventional stop-controlled intersection. A 9 percent reduction was observed in the proportion of crashes that result in injuries or fatalities.

RECOMMENDATIONS

The observational data and the crash analyses indicate that the RCUT design has a substantial safety benefit. The travel time penalty is small and would likely decrease with higher volumes of traffic on the major road.

RCUT acceleration lanes for right turns and U-turns are strongly recommended to reduce traffic conflicts and minimize the delay incurred while drivers wait for acceptable gaps in the mainline traffic.

Researchers—This study was performed by the FHWA Research, Development, and Technology Human Factors Team. The principle investigator was Vaughan W. Inman of SAIC. Robert P. Haas of SAIC co-authored the technical report.

Distribution—This TechBrief is being distributed according to a standard distribution. Direct distribution is being made to the Divisions and Resource Center.

Availability— This TechBrief may be obtained from the FHWA Product Distribution Center by email to report.center@dot.gov, fax to (301) 577-1421, phone to (301) 577-0818, or online at http://www.fhwa.dot.gov/research.

Key Words—Restricted crossing U-turn, Superstreet, J-turn, Alternative intersection design, Highway safety, Driver behavior, Divided highway, Intersection safety.

Notice—This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

Quality Assurance Statement—The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement.

 

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