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An increasing number of Accessible Pedestrian Signals (APS) have been installed at new or upgraded intersections to assist people with vision impairment to navigate streets. For un-signalized intersections and intersections without APS; people with vision impairment have to rely on their own orientation and mobility skills to gather necessary information to navigate to their destinations. Previously; a smartphone-based accessible pedestrian system was developed to support wayfinding and navigation for people with vision impairment at both signalized and un-signalized intersections. A digital map was also created to support the wayfinding app. This system allows a visually impaired pedestrian to receive signal timing and intersection geometry information from a smartphone app for wayfinding assistance. A beacon using Bluetooth Low Energy (BLE) technology helps to identify a pedestrian's location when he or she travels in a GPS-unfriendly environment. A network of Bluetooth beacons ensures that correct traffic information is provided to the visually impaired at the right location. This project leverages the previous work by installing the system at a number of intersections in downtown Stillwater; Minnesota; where MnDOT operates the signalized intersections. In this study; researchers interface with the traffic controllers to broadcast traffic signal phasing and timing (SPaT) information through a secured and private wireless network for visually impaired users. The aim is to test the smartphone-based accessible system and evaluate the effectiveness and usefulness of the system in supporting wayfinding and navigation while the visually impaired travel through signalized and un-signalized intersections.

Decisions made regarding driver sight distance at rural intersections are complex and require considerations for safety; efficiency; and environmental factors. Sight distance; cross-traffic velocity; and vehicle placements significantly affect driver judgment and behavior at these intersections. A series of rural; two-lane thru-STOP simulated intersections with differing sight distances and traffic speeds were created and then validated by county and state engineers. Experimental data from 36 participants in a time-to-collision (TTC) intersection crossing judgment task and a rural highway thru-STOP intersection driving simulation task was analyzed to clarify the influence of rural thru-STOP intersection characteristics on driving performance and decision-making. Results demonstrated that longer sight distances of1;000 ft. and slower crossing speeds (i.e.; 55 mph) were more accommodating for participants attempting to select gaps and cross from the minor road; corresponding with (1) lower mental workload; perceived risk; difficulty; and anxiousness; and (2) better performance in terms of estimated crash rate; and larger TTCs. Second; longer distances of 1;000 ft. appear to aid drivers' responsiveness on the main road approaching an intersection; specifically when another driver on the minor road runs the stop sign. Minor road drivers positioned close to the roadway at the stop sign; compared to standard stop bar placement; tended to help reduce the speed of main road drivers. Overall;results demonstrated a systematic improvement in the performance of both minor and major road drivers with the implementation of a1;000-foot sight distance at rural thru-STOP intersections.

This Transportation Research Synthesis includes the results of a survey of highway design and roadway geometry professionals regarding their knowledge and use of continuous green T-intersections (CGTs). State-level design standards and technical guidance were also requested and are included.

This is a photo of the Highway 60 J-Turn in Heron Lake, Minnesota.

Detailed Intersection Control Information (ICI); including timing; phasing; geometric; and demand attributes; is an increasingly important resource for researchers; consultants; and private sector companies for many applications; including development of traffic models and technologies such as vehicle information or automation systems. While this information has historically been difficult to distribute due to variations in the availability and format across the numerous jurisdictions that operate signals; recent trends toward increased use of Central Traffic Signal Control Systems (CTSCSs) have made creation of a unified; standardized system for organizing ICI more feasible. To help work toward this; in this project researchers interviewed and surveyed signal operation engineers and transportation modelers throughout Minnesota to learn how different jurisdictions manage information relating to their signals and how this information is used for operations and planning. With this information; researchers developed a comprehensive Unified Set of Intersection Control Information (U-ICI) that contains all the information required to describe the control of an intersection in a format that is readable by both humans and machines. Along with this; researchers evaluated the availability of this information and the feasibility of using existing CTSCS applications to store this information. While the researchers conclude that it is not feasible to use these applications to store all of the U-ICI; the applications will likely make the process of implementing and populating such a system easier. Though some information may be contained in formats that will require manual effort to digitize; the up-front effort to do so will be a worthwhile pursuit.

Past research has clearly shown that obstructed sight lines at intersections lead to greater possibilities of collisions between left-turning vehicles and opposing oncoming vehicles. Evaluations of the effects of left-turn lane offsets; reported that positive left-turn lane offsets were more effective in reducing intersection left-turn crashes than zero and negative left-turn offsets. Several researchers have developed guidelines for geometric design elements of left-turn offset. The majority of states provide only a limited discussion on this topic. Florida DOT provides the most comprehensive policies and guidance for assuring unobstructed sight lines at left-turn lanes. Recommendations developed in this project center on general policies and guidance for designing offset left-turn lanes for a new edition of MnDOT's Road Design Manual. Recommendations are organized to provide standards; policies; and guidance for new/reconstruction projects and for preservation projects. Topics covered include definition of left-turn lane offset; design factors impacting offset; suggested designs for urban and rural multilane roadways and expressways; accommodating U-turns; pedestrian and bicyclist considerations as well as winter maintenance considerations. Additional recommendations are offered to improve consistency among all MnDOT manuals and guides used for intersection design and operation.

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.

A 4-3 conversion involves changing a four-lane undivided road into one with two general travel lanes separated by a two-way left turn lane. A commonly-used guideline states that a 4-3 conversion can be considering as long as the road’s average annual daily traffic (AADT) volume does not exceed 15,000 vehicles/day but opinions vary, from lowering the AADT threshold to 10,000 vehicles/day to anecdotal evidence for successful 4-3 conversions with AADTs as high as 20,000. The main objective of this project was to identify conditions where 4-3 conversions might be feasible at AADTs greater than 15,000. After reviewing the literature, we conducted simulation studies on three different roads to identify combinations of major and minor road flow where three-lane configurations provided acceptable levels of service. Eight intersections, with 16 approaches, were then selected to represent our findings. These results were presented as summary tables that practitioners could use to make initial assessments regarding 4-3 conversion feasibility.

Pedestrian deaths are at a 30-year high nationally, accounting for 16% of total deaths in 2018 and far exceeding the previous decade of 12%, a trend mirrored in Minnesota. Previous research found an increase in local and citywide yielding at unsignalized crosswalks following an engineering and high-visibility enforcement program in Saint Paul, Minnesota. This study examined a modified engineering-focused (i.e., without enforcement) program expanded to both unsignalized and signalized intersections across the Twin Cities. The six-month study found modest improvements in yielding from baseline to treatment end (48.1% to 65.5% in Saint Paul and 19.8% to 38.8% in Minneapolis) at unsignalized engineering treatment sites but no improvements at generalization sites. No significant improvements in left- or right-turning yielding by drivers in Saint Paul were found at treated signalized intersections, but given that yielding was significantly worse at generalization sites over time, there may be some evidence that treatments mitigated performance declines among Saint Paul drivers during the study period. Yielding improvements at signalized treatment sites were more pronounced for only right-turning drivers in Minneapolis, but generalization sites showed no improvement or even worsened over time. Overall, study results suggested no shift in driving culture in either city, as found with the previous study using police enforcement, but found some evidence of local, site-specific changes in driver yielding behavior at treatment locations.

This study was driven by the need to improve consistency in the methods and approach that local agencies use to address crosswalks. This study focuses on the question of how a crosswalk should be enhanced with additional countermeasures, if any, once the decision is made to mark it. During the research portion of this project, it was found that the primary information agencies use that provides guidance for decisions on how to mark crosswalks comes from the Federal Highway Administration. A quick reference guide was developed from FHWA’s Guide for Improving Pedestrian Safety at Uncontrolled Crossing Locations, July 2018, that will help agencies determine when to use different countermeasures based on roadway type, vehicle volumes, and posted speed limits. In addition, fact sheets for twelve countermeasures identified in the document were developed to explain what the benefit of each one is, when it is best applied, and how to provide high-level planning cost for each one.