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Publication Number: FHWA-HRT-11-067
Date: June 2012

 

Field Evaluation of A Restricted Crossing U-Turn Intersection

CHAPTER 1. INTRODUCTION

BACKGROUND

Compared to grade-separated limited-access facilities, four-lane divided highways are an economical design for increasing the capacity of rural highways. Four-lane divided highways can also increase safety compared to the two-lane rural highways they often replace.[1,2] A study conducted by the Nebraska Department of Roads comparing two-lane undivided rural highways to four-lane divided highways found that the four-lane divided highways had markedly lower rates of sideswipe, rear-end, and head-on collisions. However, right-angle crashes were 71 percent more frequent at four-lane divided highway intersections than at two-lane undivided highway intersections.[3]

The restricted crossing U-turn (RCUT) intersection, which is also called the J-turn or superstreet intersection, is a promising treatment to mitigate right-angle crashes where two-lane minor roads intersect with rural four-lane divided highways. This design usually permits left turns from the divided highway onto the minor road but restricts the minor road to right turns, which may be followed by a U-turn for left-turn and through movements. Direct left turns from the highway, if allowed, are made from channelized directional-median openings. At many RCUT locations, the U-turn median openings are also directional. Figure 1 shows the RCUT that was observed in this study. A closer view of the channelization at the main intersection is shown in figure 2, and a closer view of the channelization for a directional U-turn is shown in figure 3.

Figure 1. Photo. 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.

Figure 2. Photo. Channelization for left turns from the highway and right turns from the minor road. This photo shows a satellite view of a main intersection. Channelization is shown, which prevents direct left-turn and through movements from the minor road but allows left-turn movements from the highway onto the minor road. Other features are deceleration lanes for left and right turns from the highway and acceleration lanes for right turns from the minor road.

Source: Google®, U.S. Geological Survey, Data SIO, NOAA, U.S. Navy, NGA, GEBCO.

Figure 2. Photo. Channelization for left turns from the highway and right turns from the minor road.

Figure 3. Photo. Directional U-turn channelization at the RCUT observed in this study. This photo shows a satellite view of one of the U-turn channels of the restricted crossing U-turn (RCUT) intersection observed in this study. Channelization is shown, which prevents conflicts between vehicles making U-turns from the northbound direction to the southbound direction and vehicles turning from the southbound direction to the northbound direction. Wide deceleration and acceleration lanes for U-turning vehicles are also present.

Source: Google®, U.S. Geological Survey, Data SIO, NOAA, U.S. Navy, NGA, GEBCO.

Figure 3. Photo. Directional U-turn channelization at the RCUT observed in this study.

OBJECTIVE

One objective of this study was to observe an operational RCUT 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, observations were also made at a nearby conventional intersection on the same corridor.

In particular, the observations focused on the following:

A second objective was to perform crash analyses to examine the effects of conversions on conventional intersections to RCUTs on two rural high-speed divided highway corridors in Maryland. These analyses focus on nine RCUT intersections that were deployed in Maryland between 1998 and 2003. Six of these intersections were deployed on U.S. 15 in western Maryland, and three were deployed on U.S. 301 on the Delmarva Peninsula in eastern Maryland.

 

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