Intersections

This Technical Summary pertains to Report 2022-31, “Establishing a Repeatable Method for Presenting Non-Traditional Traffic Treatments to Maximize Stakeholder Support,” published June 2023

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.

This flyer pertains to report 2016RIC10, Intersection Safety Technologies Guidebook.

The results of a study on the origins, destinations and purposes of motor vehicle transportation in the Twin Cities

This Technical Summary pertains to Report 2023-17, “Transverse Rumble Strips at Rural Intersections,” published April 2023.

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

This report presents a real-time system for pedestrian tracking in sequences of grayscale images acquired by a stationary CCD (charged-coupled devices) camera. The research objective involves integrating this system with a traffic control application, such as a pedestrian control scheme at intersections. The system outputs the spatiotemporal coordinates of each pedestrian during the period the pedestrian remains in the scene. The system processes at three levels: raw images, blobs, and pedestrians. It models blob tracking as a graph optimization problem and pedestrians as rectangular patches with a certain dynamic behavior. Kalman filtering is used to estimate pedestrian parameters. The system was implemented on a Datacube MaxVideo 20 equipped with a Datacube Max860 and on a Pentiumbased PC. The system achieved a peak performance of more than 20 frames per second. Experimental results based on indoor and outdoor scenes demonstrated the system's robustness under many difficult situations such as partial or full occlusions of pedestrians

This project sought to understand the effects of warning flashers on the safety of rural intersections. Researchers conducted four separate studies: a literature review; an opinion survey of a sample of Minnesota motorists who lived outside urban areas; an analysis of accident data for rural intersections comparing accident rates three years before and three years after the installation of various configurations of warning flashers; and a field study at the intersection of U.S. 14 with MN 52 in Eyota, Minn. This last study included a baseline period, followed by a phased implementation of various warning flasher configurations, with a week or so between phases. Researchers concluded that none of the four studies unequivocally supported the effectiveness of warning flashers at rural intersections in promoting safety at rural intersections. While driver alertness or awareness to potential hazards at the intersection may have been enhanced by the installation of warning flashers, this project did not provide data that would demonstrate such enhanced alertness or awareness.

As a low-cost countermeasure to rural intersection crashes, transverse rumble strips (TRS) provide an audible and tactile warning to drivers approaching an intersection with the primary goal of decreasing crashes that result from running a stop sign. The objective of this project is to evaluate the effectiveness of different TRS patterns on stopping behavior at rural stop-controlled intersections. Eight rural intersections in St. Louis County, Minnesota, were selected as test sites. Milled-in rumble strips were installed at the sites that varied in terms of number of panels (2 or 3) and number of rumble strips per panel (6 or 12). Speed, traffic volume, and video data were collected at each site before, 1 month after, and 9 months after TRS installation to evaluate various crash surrogate metrics. The most significant metrics affected by TRS configuration included percentage of vehicles engaging in a full/rolling stop at the intersection, change in average speeds on the approach near the intersection, percent of vehicles traveling 45 mph or more, and percent of vehicles engaging in late braking. A qualitative summary of the various metrics suggested that the 3-panel, 12-rumble strip design performed the best. Noise analyses were also conducted to assess whether the number of rumble strips per panel (6 or 12) affected exterior and in-vehicle noise. No significant differences in exterior noise were found, and both panels produced sufficient in-vehicle noise to alert a drowsy driver. As a result, noise was not a factor in selecting one panel type over another.

The previous phases of this research reviewed and tested existing intersection control algorithms in a simulated environment. Further, a machine-vision detection system with four cameras was installed at the intersection of Franklin and Lyndale Avenues in Minneapolis, Minnesota, to develop a live intersection laboratory. Phase III enhanced the live laboratory with two additional cameras covering the intersection proper and the extended approach of southbound Lyndale Ave. A comprehensive operational plan for the laboratory was developed and a new microscopic simulator for the laboratory intersection was -also developed. Two types of new intersection control strategies, i.e., one with link-wide congestion measurements and the other based on neural-network approach, were developed and evaluated in the simulated environment. Further, using the data collected from the machine-vision detection system, an automatic procedure to estimate the intersection delay was also developed and applied to compare the performance of fixed-timing control with that of the actuated control strategy.