MnDOT and Local Road Research Board

Studies by the Federal Highway Administration show that American Indians have higher rates of pedestrian injury and death per capita than any other population group in the United States. The Minnesota Department of Transportation (MnDOT) has identified Native Americans as one of six priority populations in Minnesota that face disproportionate risks as pedestrians. This report summarizes efforts taken between 2016 and 2024 to document and reduce risks to pedestrians on the seven recognized Anishinaabe reservations in Minnesota. Across reservations, researchers monitored pedestrian crossings using video recorders at 23 different sites identified by Tribal transportation managers, including 10 Phase 1 sites (2016-2020) and 13 Phase 2 sites (2019-2024). Monitoring results, including pedestrian counts, interactions with drivers, and yield rates, were used to inform planning and implementation of countermeasures to reduce crash risk at six Phase 1 sites and two Phase 2 sites. These countermeasures included marked crosswalks with pedestrian landing pads, better lighting and signage; ADA-accessible pedestrian access ramps; and a pedestrian hybrid beacon. Additional countermeasures have been scheduled or planned for 2024 or later at six more locations. Post-implementation monitoring at six Phase 1 sites confirmed that countermeasures change pedestrian and driver behaviors, but not all pedestrians or drivers use countermeasures as designed. Implementation of countermeasures may change risk factors and reduce risks, but risks cannot be eliminated and will remain after countermeasures are implemented. Consultation, coordination, and cooperation among Tribal, state, and local transportation planners and engineers are essential to reducing crash risk and increasing pedestrian safety.

This research summary accompanies Report 2024-13 "Complete Streets Speed Impacts," published June 2024.

This research summary accompanies Report 2024-14, "Evaluation of Traffic Safety for Heavy Commercial Vehicles at Roundabouts in Minnesota," published in May 2024.

This research summary accompanies Report 2024-10, "Performance Evaluation of Different Detection Technologies for Signalized Intersections in Minnesota," published April 2024.

The I-35W traffic management system has been in operation for over seven years. The purpose of the project was to implement and evaluate the Bus-on-Metered Freeway System. A number of reports have been published documenting the design details, system hardware and software, system operation and evaluation of the Bus-on-Metered Freeway concept. A listing of these reports is presented in the Appendix. Appendix also includes a list of reports dealing with incident detection and/or incidents impact on capacity. One of the specific objectives within the system framework was to quickly detect incidents occurring on the freeway and provide information to the appropriate response agency so that freeway capacity reducing and hazard causing incidents could be removed as soon as possible. The purpose of this study is twofold: first, available incident records accumulated on the I-35W freeway traffic management system will be analyzed to develop a comprehensive view of the types and quantities of incidents that have occurred. Second, the incident data base and companion volume and occupancy data will be used to determine the impact of "typical" incidents and the impact of the total incident problem. Included in the report is an analysis of incident types detected, mode of incident detection, duration of incidents, and incident response activities.

Recently, speed management practices have shifted away from an historical focus on the 85th percentile speed toward a safe systems approach that is focused on promoting safer speeds in all roadway environments through a combination of thoughtful, equitable, context-appropriate roadway design, appropriate speed-limit setting, targeted education, outreach campaigns, and enforcement. This includes the incorporation of a Complete Streets approach to roadway design, which uses cross-sectional characteristics that reduce speeds and create a more accommodating environment for people biking and walking. This study aims to inform this design process by advancing our understanding of how drivers adjust their speeds based on changes in the posted speed limit and other contextual factors related to the roadway environment. Field data were collected from 19 highway corridors across Minnesota using handheld lidar guns to track drivers' operating speeds as they transitioned from high-speed rural highways to lower-speed rural and suburban communities. The study results in the estimation of a series of speed reduction factors (SRF), which detail the impacts of various site-specific characteristics on travel speeds. Various features are shown to serve as effective speed-control measures, such as single-lane roundabouts, which reduced speeds by about 7 mph. Speeds were also lower on segments that included two-way, left-turn lanes (0.7mph), depressed medians (1.2 mph), and raised medians (3.1 mph). The results also show that drivers typically begin reducing their speeds approximately 800 ft upstream of posted speed limit signs and continue to reduce their speeds to a distance 400 ft beyond the sign location. Ultimately, this study will allow for a more proactive and data-driven approach to highway design that considers the needs of all users.

This study examined the operation of static and dynamic no right turn on red (NRTOR) signs at eight signalized intersections in Minnesota (six dynamic and two static). Driver compliance with the NRTOR indications were measured using video data. Most dynamic NRTOR sign locations were pedestrian-activated, with one location having additional time-of-day activation of the NRTOR indication. Compliance rates were calculated per signal cycle and per vehicle. Per-cycle compliance rates were 60.8% for dynamic and 80.0% for static sign locations, while per-vehicle compliance rates were 87.1% for dynamic and 92.4% for static sign locations. Statistical models were further developed to confirm the statistical significance of the results and to explore the strength of the effect compared to other intersection characteristics. A survey of practitioners was included to identify the installation and maintenance costs of DNRTOR devices. The report concludes with recommendations on uses of DNRTOR.

This Research Summary is part of Report 2024-08, "Effect of Increased Precipitation (Heavy Rain Events) on Minnesota Pavement Foundations," published April 2024.

Base stabilization additives are used to increase the strength and stiffness of road foundations on weak and susceptible soils. The Minnesota Department of Transportation (MnDOT) quantifies the structural contribution of pavement layers by introducing granular equivalency (GE) factors. While numerous additives exist for improving the performance of aggregate base layers, this study focuses on proprietary additives including Base One, Claycrete, EMC SQUARED, PennzSuppress and Roadbond EN1. The laboratory study revealed that EMC SQUARED was the superior stabilizer, with an optimum dosage set 15% higher than the manufacturer recommended dosage (MRD). The long-term performance of proprietary additives was monitored by considering full-scale field implementation with optimum additive dosages obtained from laboratory investigation. Controlled sections without stabilization exhibited higher values in the California Bearing Ratio (CBR) and composite elastic modulus right after construction, while the impact of stabilizers on the increasing strength of the full depth reclaimed (FDR) base was revealed after two years of construction. Falling-Weight Deflectometer (FWD) tests demonstrated a progressive increase in the stiffness of stabilized sections over time, surpassing the control section's stiffness after two years. The economic analysis utilizing Life Cycle Cost Analysis (LCCA) indicated that stabilized sections, particularly those treated with EMC SQUARED, offered lower Equivalent Uniform Annual Cost (EUAC) values across various maintenance scenarios. These findings suggested potential cost savings over a pavement's life cycle with higher GE factors of recycled asphalt pavement base aggregate treated with proprietary additives. The findings will contribute to a comprehensive understanding of the benefits, feasibility, and design considerations associated with using commercial stabilizers in FDR base layers.

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