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The Minnesota Department of Transportation (Mn/DOT) has concluded that at certain high speed locations, providing additional information to the motorist describing the operation of the traffic signal can assist the driver in making safer and more efficient driving decisions. The additional information includes a visual indication to get the driver's attention and a specific notice that the driver must prepare to stop. The Advance Warning Flasher (AWF) is a device which Mn/DOT uses to convey this information to the driver. The Mn/DOT A WF system consists of a flasher and a sign located on main street approaches to a high speed signalized intersection. The AWF is connected to the traffic signal in such a way that when the main street green is about to change to yellow, the flasher is turned on to warn the approaching drivers of the impending change. Basically, the purpose of an optimally designed combination of traffic signal and AWF system is twofold: 1) to inform the driver in advance of a required driver decision (prepare to stop) and 2) to minimize the number of drivers that will be required to make that decision. Over time, questions have arisen regarding the use and application of AWF devices. The purpose of this study was to examine the effectiveness of the current AWF operation and, where possible, to make recommendations to improve it. The study concluded that the use of AWF devices can be effective at reducing right angle and rear end accidents under certain situations but that the device does not automatically increase the safety of all intersections. Accordingly the device should be considered as a traffic engineering tool to be used to correct situations of special need. Further, this study developed a scheme to optimize AWF operation. The proposed approach will theoretically produce an optimized A WF location/operations scheme but must be field validated as part of a suitable test study.

Among the most promising and innovative concepts today for alleviating urban traffic congestion is the use of video imaging for vehicle detection, automatic surveillance, and advanced control strategies. Because of its conceptual appeal, research in this area was initiated in the mid 70's in the United States and abroad. A system for vehicle detection through video imaging was recently developed at the University of Minnesota and is being implemented on the 1-394 and l-35W freeways in Minneapolis, Minnesota for incident detection. The Minnesota system, called AUTOSCOPE (TM), emulates loop detectors, a large number of which can easily be placed within the field of the camera's view through interactive graphics. In recent tests its performance matched or exceeded that of loops in vehicle counting, speed measurements, and extraction of certain measures of effectiveness. Evaluation tests of the AUTOSCOPE (TM) were very encouraging, thus the system was installed at a traffic intersection to demonstrate the effectiveness of this new technology as a replacement for loop detectors.

This Technical Summary pertains to Report 2023-11, “Multi-City Study of an Engineering and Outreach Program to Increase Driver Yielding at Signalized and Unsignalized Crosswalks,” published January 2023.

This project evaluates various intersection control strategies in a simulated environment and also helped establish a live laboratory for use in future testing of new control strategies. The report reviews major intersection control strategies, including the state-of-the-art strategies with adaptive and on-line timing generation features. In addition, it details simulation results for the OPAC control strategy. The NETSIM simulator created the simulation environment for a test network that included part of downtown Minneapolis. Comparison results indicate that OPAC performs best with low-traffic demands, and pretimed control was the most effective during peak periods when traffic demand reached capacity. In conjunction with this project, Minneapolis city traffic engineers installed a machine-vision video detection system at a live intersection laboratory. Located at Franklin and Lyndale Avenues, the test site will help researchers evaluate new control strategies before full-scale implementation in later phases of this research. The Phase I report is available at https://hdl.handle.net/11299/155938.

The data collection worksheets in this spreadsheet pertain to report 2014-21, Uncontrolled Pedestrian Crossing Evaluation Incorporating Highway Capacity Manual Unsignalized Pedestrian Crossing Analysis Methodology.

This Research Summary accompanies Report 2024-05, "Traffic Safety Evaluation at J-turns in Minnesota," published February 2024.

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.

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.

Many factors influence an individual driver’s decision to yield or not yield to individual pedestrians attempting to cross the road at an unsignalized crossing. This study collects observational data from more than 3,300 crossing events at 18 intersections in Minnesota to further our understanding of what factors positively influence driver yielding. Using the collected data, a statistical analysis was conducted to identify features that most strongly correlate with driver yielding. Event specific features such as speed were found to greatly influence yielding, with vehicles traveling at a speed of greater than 25 mph significantly less likely to yield to pedestrians than vehicles traveling at speeds lower than 25 mph. Site-specific features such as the presence of signs indicating a crossing were also strongly correlated with driver yielding. The results provide indication of which features of unsignalized crossings correlate with higher driver yielding rates. These findings can be used to guide policy and design at sites where a high driver yielding rate is desirable.

This research summary was created as part of Report 2023-24, "Guidelines for safer pedestrian crossings: Understanding the factors that positively influence vehicle yielding to pedestrians at unsignalized intersections," published June 2023.