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Median U-turns

A Median U-turn (MUT) is a type of intersection in which some left-turns or crossings from the mainline road or secondary crossroad are made using indirect, downstream U-turn movements. Intersections of this type are common and have performed successfully in other states, notably Georgia, Maryland, Michigan, Minnesota, Missouri, and North Carolina.

MUTs are a subset of design styles referred to as alternative, non-traditional, or innovative intersections, which also include roundabout, continuous green T, quadrant roadway, and displaced left intersections. While they differ in style, what these designs all share is a reduced number of conflicting traffic movements in comparison to traditional intersections, and that characteristic improves safety performance and lowers travel delay where certain traffic and site conditions are present.

There are three basic forms of a MUT intersection. Each is unique, but all feature U-turns after the primary intersection. They are a Restricted Crossing U-turn (RCUT), Reduced Conflict Intersection (RCI), and Boulevard Left.

Under the right traffic conditions, MUTs are proven to improve safety and reduce delay by separating and simplifying traffic movements. MUT intersections improve the ability of traffic to cross a multilane divided highway from a crossroad, and reduce the number of traffic signal phases, which frees up green time for more critical traffic movements through the primary intersection.

MUTs are generally limited to locations where the main road has four or more through lanes divided by a median. They may be used in rural or urban areas under high- or low-speed conditions and may or may not include traffic signals. They may be used individually or in a series along a corridor.

All MUT-style crossings include a companion U-turn location away from the primary intersection to complete what would ordinarily be a direct left-turn or direct through movement from the crossroad.

MUT intersections are designed to fully accommodate the wide turning radius of tractor-trailer trucks and other large vehicles, such as school buses. Where road and median width is not sufficient to accommodate larger vehicles, an additional pavement area is added. Special provisions are also made for police, fire trucks, and other emergency vehicles to cross the intersection without making U-turns. MUT intersections maintain full service to pedestrians and bicyclists. The cost to retrofit a regular intersection to a MUT ranges from a few hundred thousand dollars to more than $1 million.

In June 2015, INDOT opened its first MUT intersection — a RCI — at U.S. 41 and State Road 114 in Newton County. By mid-2019, six more had been built. Others are planned where crash history, traffic volumes, and other road conditions justify the design.

INDOT’s policy is to use alternative intersections, including the Median U-turn, where appropriate to support its ongoing commitment to improve safety and service delivery through innovation and cost-effective investments.

MUT Intersection Styles

The three different MUT-style intersections differ in how left turns or through movements are re-directed to the U-turn locations and whether crossroad traffic is controlled by traffic signals, stop signs, or yield signs.

With a RCUT, the main intersection is controlled with a signal and, in some cases, the U-turns are signal-controlled as well. A RCI has no traffic signal, only stop or yield signs. Apart from the presence or non-presence of traffic signals, the two forms look and function similarly and both typically permit direct left turns from the mainline. However, there is a RCI variation that does not permit direct mainline left turns. In both RCUT intersections and RCIs, crossroad traffic wanting to turn left or pass through makes an indirect U-turn movement. Through movements for mainline traffic and right turns are made the same way as in a conventional intersection.

Although a RCUT and RCI look similar, other than presence or non-presence of traffic signals, they differ significantly in application, principally in their traffic volume carrying capacity and setting. RCUT intersections and RCIs are labeled various ways in different states, such as superstreet, J-turn, and synchronized street.

The Boulevard Left intersection differs from a RCUT intersection or RCI in two ways: Direct left turns from the mainline are not permitted but occur beyond the primary intersection at the U-turn, and through movements from the crossroad are permitted. Boulevard Lefts go by different names across the country, including Michigan left and thru-turn.

Drivers approaching a Boulevard Left intersection from the crossroad make a left turn by first turning right, and then making a downstream U-turn. A variant of this intersection requires both the primary and secondary roads to travel through the primary intersection before making left turns at the downstream U-turns. In either case, all through and right-turn movements at a Boulevard Left are the same as a conventional intersection. With a Boulevard Left, traffic at the primary intersection is ordinarily controlled by a traffic signal, and U-turn locations may be controlled by yield signs, stop signs, or a signal in coordination with the main intersection.

Improved Safety

MUT intersections significantly reduce the risk of severe crashes in certain traffic and road conditions. MUTs increase safety by reducing by half or more the number of possible conflicts and the points where two vehicle paths cross. 

In a traditional intersection there are 42 different conflict points where an accident can occur. Of those, 24 conflict points can cause serious T-bone or right angle crashes – the crashes most responsible for fatalities and serious injuries at intersections. A MUT intersection can have no more than 29 possible conflict points and some MUT intersections can be designed so that there are zero crossing conflict points.

RCIs eliminate the need for motorists to cross the high-speed lanes of traffic to get to the opposing lanes. Nationwide, statistics show a more than 50% decline in crashes where RCIs are installed. Fatal crashes decline by as much as 85%.

Recent Statistics

Since 2015, INDOT has installed seven RCIs at four-lane highway intersections in Indiana. These intersections have shown a substantial decrease in fatal and injury crashes since RCI installation.

INDOT has conducted performance analyses of crashes at each RCI, comparing pre-construction crash frequency and severity with post-construction data over similar time periods, ranging from 1½ to 5 years.

In overall effectiveness, INDOT’s analysis showed that the seven RCIs:

  • Reduced fatal and injury crashes by an average of 81%.
  • Reduced property-damage crashes by an average of 58%.
  • Reduced crashes of any severity by an average of 68%.

INDOT’s analysis showed a dramatic reduction in fatal and injury vehicle crashes at each RCI:

  • Fatal and injury crashes at each intersection declined between 64% and 100%.
  • Property-damage crashes at each intersection ranged from No Change to 100% reduction.
  • All crashes of any severity at each intersection declined between 38% and 100%.

INDOT continues to track the safety performance of these and future RCIs to assess their effectiveness and advance our understanding of the traffic levels, design, and site conditions most suitable for this highway feature.

Improved Capacity

MUT intersections not only improve safety but reduce intersection delay and overall travel time when operating under the right traffic and road conditions. Although drivers have to travel slightly further to get where they want to go, using MUT intersections can require the same or less time than trying to wait for a safe and appropriate gap to cross traffic. For the RCUT and Boulevard Left, retrofitting a standard intersection will improve traffic capacity by 20% to 50%. This improved traffic capacity is achieved through more efficient traffic signal operation, including better phasing, timing, and progression or coordination with adjacent intersections. Stops are reduced by a third or more.

Driving a MUT

The MUT intersection design eliminates the cross-over between the four-lane divided highway. In the RCI design, drivers turn right in the same direction of traffic and merge safely into the left lane to prepare to make a left turn in the direction they intended to travel. This option uses an extended deceleration lane, basically adding a third lane on the highway to allow motorists making a left turn onto opposing lanes to safely pull off the main line, out of the way of high-speed traffic.

MUT Advantages

When operating under the right traffic and field conditions, advantages of the MUT intersection over a standard intersection design include:

  • Significant reduction in the risk of crashes due to a decrease in potential conflict points, particularly for angle crashes that tend to be severe.
  • Increased capacity, reduced delay, and fewer stops overall. In some cases, there is even shorter travel time for traffic movements re-directed through the U-turn.
  • Low cost in relation to conventional intersection construction or modernization and to other non-traditional intersection designs.
  • Often can be retrofitted to an existing intersection without the need for additional land.
  • Relatively straightforward to expand in the future, if necessary.
  • A RCI may permit an existing traffic signal to be removed, or may delay the need for future signal control.

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www.indot4u.com
1-855-INDOT4U (1-855-463-6848)
INDOT@indot.in.gov

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