Innovative Approaches to Intersections

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Date Created
2008-01
Report Number
P2008-01
Description
After visiting a variety of stop-controlled intersections in the Twin City metro area, the researchers developed, with the aid of a computer simulator, two innovative intersection designs to improve safety at unsignalized intersections on four-land, divided highways. These innovative designs offer a number of advantages; however, due to funding difficulties, the researchers were not able to test the effectiveness of the designs in a real world setting.

Traffic Safety Evaluation at J-turns in Minnesota

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Date Created
2024-02
Report Number
2024-05
Description
Between 2010 and 2022, 83 J-turn intersections were installed on Minnesota Department of Transportation (MnDOT) roadways. The J-turn is an alternative intersection layout that is intended to provide safety benefits by limiting the number of points within an intersection that two or more vehicle paths might intersect. Before-after analyses at J-turns and control sites were conducted and compared. With the installation of a J-turn, the analyses found decreases in fatal and serious injury crashes, angle crashes, and fatal and serious injury angle crashes. The large decreases in severe crashes at J-turn locations indicate the J-turn can be an effective safety treatment. The analysis also found J-turns have lower crash rates for key crash types as compared to low-volume interchanges and rural, high-speed signalized intersections.

Traffic Safety Evaluation of Lane Constrictor Intersections in Minnesota

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Date Created
2024-02
Report Number
2024-03
Description
Between 2018 and 2019, MnDOT installed a lane constrictor design at 66 side-street, stop-controlled intersections in Minnesota. The lane constrictor design narrows the lane width for mainline approaches via a striped median with centerline rumble strips. By narrowing the mainline lane, the goal of this design is to encourage mainline traffic to slow down as it approaches the intersection. The striped median also provides greater separation between mainline directions and draws more attention to the location of the intersection. Following the installation of lane constrictors at MnDOT intersections, overall crash rates have seen little change but there have been decreases in fatal and serious injury (KA) as well as fatal and all injury (KABC) crash rates. These results indicate the addition of lane constrictors have a positive impact on crashes by reducing the severity of crashes, swapping injury crashes for property damage only crashes.

Traffic Safety Evaluation of Signalized Intersections with Retroreflective Backplates in Minnesota

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Date Created
2024-01
Report Number
2024-04
Description
Between 2016 and 2021, MnDOT installed retroreflective signal backplate borders at 116 signalized intersections in Minnesota. Retroreflective signal backplate borders are intended to further increase visibility of the signal head both during the day and at night. The goal of installing retroreflectivity to backplates is to reduce crashes at the intersection by drawing more attention to the current phase of the signal. Backplates with retroreflective borders are listed as a Federal Highway Administration Proven Safety Countermeasure with a listed safety benefit of a 15% reduction in total crashes. With the installation of retroreflective signal backplates on MnDOT signals, the changes in crash rates were not found to be statistically significantly different from similar locations that did not have retroreflective signal backplates. These results indicate there has been little impact on crash rates in the few years after the installation of retroreflective signal backplates.

Establishing a Repeatable Method for Presenting Nontraditional Traffic Treatments to Maximize Stakeholder Support

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Date Created
2023-08
Report Number
2022-31
Description
A novel infrastructure design known as the J-turn intersection reduces the risk of serious and fatal crashes at thru-STOP intersections through decreasing points of conflict at an intersection by restricting crossing movements from the minor road. Despite their demonstrated safety efficacy, J-turns have not been met with uniformly positive support. In this research, we first examine novice driver baseline attitudes and driving behaviors on J-turns using a driving simulator study. Results demonstrate that critical errors are decreased with driving exposure to the J-turn; however, attitudes toward J-turns are not improved by exposure alone. A series of studies then evaluates the efficacy of various messaging strategies and educational materials on improving attitudes toward J-turns. The findings from these studies identify that the use of both educational materials and persuasive and customized messaging strategies is an effective method for increasing acceptance of J-turns across diverse resident populations (i.e., rural, suburban, and urban) and among stakeholders in Minnesota. This work demonstrates the importance of the role of proactive educational programs and community initiatives in promoting the acceptance and buy-in toward novel roadway treatments, such as J-turns, among diverse drivers, communities, and stakeholder groups.

The Use of Traffic Control at Low Volume Intersections in Minnesota

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Date Created
1998-08
Report Number
1998-23
Description
The Minnesota Department of Transportation (Mn/DOT) studied the use of traffic control at low volume intersections to determine the crash experience at intersections with stop, yield, and no control for low and high speed conditions, as well as analyzing crash data to develop conclusions and recommendations. Researchers sent survey forms to seven Mn/DOT districts, 87 counties, and 119 cities to collect intersection data and analyzed crash reports at selected intersections. At low speed intersections, those with stop control experienced the fewest number of accidents. However, yield control and no control can be effective methods of traffic control. At high speed intersections, the type of control had no appreciable effect on crash experience. The report suggested that uncontrolled and yield controlled intersections with three or more crashes associated with the right-of-way control in the last three years be studied to determine the need for more control