Tag Archives: MnDOT

Materials and Construction, research

New Project: Evaluating and implementing ground penetrating radar for monitoring moisture fluctuations in in-service roads

Leave a comment

Moisture fluctuations within pavement foundations—driven by rainfall, freeze–thaw cycles, and groundwater changes—can significantly impact pavement performance, especially on Minnesota’s low volume roads. Traditional moisture measurement methods, such as in place sensors or falling weight deflectometer testing, tend to be costly, intrusive, slow, and offer limited spatial coverage. Ground penetrating radar (GPR), however, provides a faster, non-invasive, and more affordable way to assess subsurface moisture over large areas, making it particularly useful for local agencies with limited resources.

To receive email updates about this project, visit MnDOT’s Office of Research & Innovation to subscribe.

This research aims to advance the validation and practical use of GPR for evaluating pavement moisture in real‑world low‑volume road settings. The study includes conducting GPR surveys on test sections equipped with moisture sensors, comparing datasets, and assessing how effectively GPR can identify areas affected by drainage or moisture issues. To support broader implementation, the project also involves creating an automatic detection algorithm capable of identifying moisture variations in unbound pavement layers.

The algorithm will be refined into a user‑friendly software tool featuring modular code, a graphical interface, and documentation. Ultimately, the project will deliver implementation recommendations designed to strengthen decision‑support tools and technical guidelines, helping Minnesota’s transportation agencies more effectively monitor and manage pavement moisture conditions.

“For this research to reach its full potential, participation from local engineers and practitioners is essential,” said Eyoab Zegeye, research operation engineer at MnDOT’s Office of Materials and Road Research. “Based on our encouraging findings, the next step is to evaluate whether this approach could be implemented on real low‑volume roads and develop testing and reporting protocols that can be quickly adopted by local agencies. County and municipal staff have the closest understanding of their road networks, challenges, and resource limitations. Their involvement ensures that the tools developed are realistic, usable, and aligned with real‑world needs.”

The Objectives:

  1. Validate and implement GPR-based pavement moisture assessment methods on low-volume roads.
  2. Evaluate GPR’s ability to efficiently survey large pavement areas and monitor moisture conditions.
  3. Identify pavement sections potentially affected by drainage issues using GPR data.
  4. Conduct GPR surveys on low-volume road test sections equipped with in-situ moisture sensors and compare the results.
  5. Develop an automatic detection algorithm to evaluate moisture variation within unbound pavement layers.
  6. Validate the algorithm and implement it as software with modularized code, a graphical user interface, and a user manual.
  7. Produce implementation recommendations to enhance decision-support tools and technical guidelines for assessing moisture fluctuations in Minnesota’s low-volume roads.

Project Details:

  • Estimated Start Date: 7/16/2025
  • Estimated Completion Date: 6/30/2027
  • Funding: MnDOT and Local Road Research Board
  • Principal Investigator: Halil Ceylan
  • Co-Principal Investigators: Sunghwan Kim
  • Technical Liaison:  Eyoab Zegeye

Details of the research study work plan and timeline are subject to change.

To receive email updates about this project, visit MnDOT’s Office of Research & Innovation to subscribe.

Traffic and Safety

Upstream and Downstream Traffic Calming Benefits of Roundabouts

Leave a comment

Roundabouts have been repeatedly shown to reduce fatal and serious crashes, in part by slowing vehicles as they move through intersections. Less was known, however, about how far those speed-reducing effects extend beyond the intersection itself or how they compare with other intersection types. To better understand these upstream and downstream impacts, MnDOT and local transportation agencies worked with investigators to measure vehicle speeds at roundabouts, signalized intersections and all-way stop-controlled intersections. The results showed that roundabouts provide traffic calming benefits beyond the intersection, supporting their continued use as a safe and effective design alternative.

Continue reading Upstream and Downstream Traffic Calming Benefits of Roundabouts →
Materials and Construction

Incorporating Environmental Assessments of Paving Roadways 

Leave a comment

To limit the environmental impacts of transportation projects, agencies need to identify the sources of greenhouse gas emissions throughout a project’s life cycle. By identifying specific sources and activities that generate emissions, the Minnesota Department of Transportation (MnDOT) can take steps to reduce its carbon footprint. This project explored the use of life cycle assessments and Environmental Product Declarations to measure and reduce the emissions associated with MnDOT paving projects, specifically the transportation of asphalt from production plants to job sites and subsequent paving activities.

Continue reading Incorporating Environmental Assessments of Paving Roadways  →
research, Traffic and Safety

Research finds pedestrian-focused infrastructure can boost safety

Leave a comment

Article reprinted from CTS News, August 12, 2026.

Published MnDOT Report: Behavioral Investigation of Temporary and Permanent Pedestrian Infrastructure

Pedestrian injuries and fatalities have significant personal, societal, and financial impacts, making it crucial to identify effective strategies to improve pedestrian safety. A research project by the UMN’s Human Factors Safety Laboratory (HFSL) evaluated the effectiveness of both temporary (i.e., quick-build) and permanent pedestrian-focused intersection features, such as curb extensions and pedestrian refuge islands. Researchers sought to understand how these features changed pedestrian and driver behavior — and how that affected safety.

Minnesota, in line with nationwide trends, saw an increase in pedestrian deaths between 2013 and 2022 (from 1.55 to 2.33 deaths per 100,000 nationwide). Similar high-income countries generally experienced a decrease in pedestrian deaths in the same period. “This remains a hot-button topic for research in the traffic safety space,” said HFSL research associate Curtis Craig, lead investigator on the project and CTS scholar, in a webinar discussing the research. The project was sponsored by the Minnesota Department of Transportation and the Minnesota Local Road Research Board.

Several unique factors make U.S. roadways especially challenging for pedestrians. “The high incidence of large trucks and SUVs makes it more difficult to see pedestrians, and any impact would be more severe because of the greater mass and geometry of the front grills on those vehicles,” Craig said. “There’s also simply a large preponderance of high-speed, multi-lane roads, which is a high-risk factor for pedestrians and drivers.”

Pedestrian-friendly infrastructure strategies aim to reduce those risks. With guidance from Minneapolis’s Vision Zero 2023–2024 pedestrian safety plan, researchers identified 12 intersections in Minneapolis and St. Paul to study before and after the installation of quick-build pedestrian infrastructure and concrete infrastructure. Quick-build infrastructure includes temporary or plastic features, such as bollards replicating bump-outs and sidewalk extensions. The goal of the study was to compare the safety influence on driver behavior of these quick-build features with those of permanent concrete infrastructure.

The study evaluated a mix of signalized and unsignalized intersections with temporary and permanent infrastructure features in a variety of income areas and with various levels of pedestrian and vehicle traffic. The team recorded driver behavior in pass-through and right-turn intersections. Data was collected in staged and natural pedestrian crossings using both in-person observations and video to record driver speeds, stops, and pedestrian behavior. The video footage was analyzed with the help of artificial intelligence algorithms.

The study found that whether permanent or temporary, the presence of the installations generally improved the rates of drivers stopping for pedestrians and led to a small but significant decline in traffic speeds at intersections. Temporary median refuges reduced the average speeds of drivers in free-flowing traffic at both signalized and unsignalized intersections. Since high driver speed is associated with a higher likelihood of pedestrian fatalities and higher injury severity, this is an especially meaningful benefit, Craig noted.

However, using flexible delineators as temporary curb extensions slightly reduced the likelihood of drivers stopping for pedestrians compared to permanent infrastructure, particularly at signalized intersections. The researchers noted a decline in stopping rates, for right-turning drivers at signalized intersections outfitted with temporary curb extensions, while the permanent, concrete curb extensions appeared to perform slightly better. The researchers speculated that the presence of bollards or other features surrounding the temporary infrastructure created a distraction, or “clutter,” that diverted drivers’ attention away from pedestrians as they navigated the intersection turn. “It’s a more visually complex environment, with more cars and more pedestrians to look out for,” Craig said.

The flexible delineators used cost between $30 and $100 each plus labor for installation, and most intersections require 12 delineators. Meanwhile, permanent concrete extensions cost about $18,000 each (or more if installation requires interaction with the sewage system) and median islands cost as much as $55,000. However, the study emphasizes that fatal pedestrian crashes have a tremendous cost. Beyond devastating personal and societal impacts, researchers point to a 2020 assessment by the U.S. Centers for Disease Control and Prevention that tallied more than $68 million in medical and work-loss costs related to pedestrian fatalities.

No two intersections in the study could be considered identical; the presence or lack of on-street parking, construction, and variations in pedestrian behaviors influenced each crossing. Craig said that future engineering projects considering the use of quick-build infrastructure need to weigh the many variables that define each intersection. Ultimately, when transportation infrastructure prioritizes pedestrians, public safety improves on Minnesota’s streets.

—Amy Goetzman, contributing writer

Related MnDOT research

Many MnDOT and LRRB projects have looked at pedestrian safety. Here is a sample of them.

Bridges and Structures, research

Evaluating a New Low Slump Concrete for Bridge Decks 

Leave a comment

For over 30 years, MnDOT has used the same low slump concrete overlay mixture to extend the service life of bridge decks. However, MnDOT suspected that changes in the materials used in the mixture over time may have contributed to increased cracking. This project evaluated a new mixture design, with and without glass fibers, to reduce cracking, improve sustainability and lower costs.

Continue reading Evaluating a New Low Slump Concrete for Bridge Decks  →
Materials and Construction, research

New Project: Design guidance and best practices for the use of light fill for sustainable road construction

Leave a comment

Lightweight Fill (LWF) materials—including Tire Derived Aggregates (TDAs), expanded shale/clay, foamed glass, and recycled glass aggregates—show strong potential for sustainable road construction, yet important knowledge gaps remain. Their environmental impacts, long‑term performance, and construction requirements are not fully understood, especially under Minnesota’s freeze‑thaw cycles and high groundwater conditions. Concerns such as leachate production, potential trench settlement, and challenges faced by local road departments highlight the need for further investigation.

To receive email updates about this project, visit MnDOT’s Office of Research & Innovation to subscribe.

This research seeks to address these gaps by reviewing existing practices, evaluating both environmental and mechanical performance, and developing data‑driven recommendations for using LWF materials in road construction. A detailed assessment will help clarify how these materials behave in pavement structures and embankments and how they interact with water‑sensitive environments. A decision matrix will be used to compare LWF materials and support future project planning.

To achieve these goals, the study will evaluate environmental impacts such as leachate risks, analyze long‑term structural integrity, and conduct Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) to assess sustainability and financial feasibility. The research will also develop recommended construction techniques that improve performance and support Minnesota’s climate goals and broader sustainability initiatives.

“Lightweight fill materials show promise for sustainable road construction, and Minnesota looks to learn from what has been done previously,” said Andrew Witter, Sherburne County Public Works Director and County Engineer. “This project will evaluate how these materials behave in local conditions and develop guidance for local counties and cities. The results will help agencies make informed decisions for the benefit of the transportation infrastructure in Minnesota.”

The Objectives:

  1. Document existing research and practices related to LWF materials in road construction.
  2. Evaluate the environmental impacts of LWF materials, focusing on leachate risks and interactions with water-sensitive environments.
  3. Analyze the long-term performance and structural integrity of LWF materials in both pavement structures and embankments.
  4. Compare LWF materials in a decision matrix to guide future project decisions.
  5. Perform Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) to assess the sustainability and financial feasibility of LWF materials.
  6. Provide recommendations to develop construction techniques that optimize the use of LWF materials and align with Minnesota’s climate goals and broader sustainability initiatives.

Project Details:

  • Estimated Start Date: 06/25/2025
  • Estimated Completion Date: 06/30/2027
  • Funding: Local Road Research Board
  • Principal Investigator: Michele Lanotte
  • Co-Principal Investigators: Angela Farina
  • Technical Liaison: Andrew Witter

Details of the research study work plan and timeline are subject to change.

To receive email updates about this project, visit MnDOT’s Office of Research & Innovation to subscribe.

research, Traffic and Safety

New Project: Does lowering speed limits reduce driver speeds on urban streets?

Leave a comment

In 2019, the Minnesota Legislature passed a law reducing barriers for cities to systematically lower speed limits. The City of St. Louis Park followed this guidance by reducing speed limits in 2021, but initial speed data collected before and 6–8 months after the changes showed little to no short‑term impact. Because driver behavior is habitual and may change slowly, advocates suggest that greater reductions in operating speeds may emerge over time, highlighting the need for repeat monitoring between 2025 and 2027.

To receive email updates about this project, visit MnDOT’s Office of Research & Innovation to subscribe.

This study aims to evaluate whether longer‑term changes have occurred 2–4 years after the initial reductions, while also examining other Minnesota agencies that have implemented or are considering reduced speed limits. The research will gather both measured and anecdotal data, assess “after” speed conditions where needed, and analyze how effectiveness varies based on roadway characteristics and any accompanying speed reduction countermeasures. These efforts address lingering questions about how speed limit changes influence driver behavior and roadway safety over time.

Understanding speed is critical because it directly affects the safety of all road users. According to Minnesota Motor Vehicle Crash Facts 2022, speeding was the leading cause of traffic fatalities, contributing to 130 of the state’s 444 deaths. By identifying agencies that have reduced speed limits, evaluating short‑ and long‑term impacts, and analyzing site‑specific factors, this research will produce guidance to help Minnesota road agencies assess and implement effective speed limit reductions.

“There is renewed interest in lower speed limits on municipal-type streets,” said Victor Lund, traffic engineer with St. Louis County’s Public Works Department. “The objective of this research is to better understand the intersection of speed limit policy, driver behavior and safety, which will result in guidance to better inform policies, practices and speed limits that support safer streets.”

The Objectives:

  1. Identify local agencies in Minnesota that have implemented reduced speed limits or may consider implementation along with any speed reduction countermeasures that have been implemented with the reduced speed limits.
  2. Evaluate the short-term and long-term effects of speed limit reductions implemented in Minnesota through the collection and analysis of speed data.
  3. Assess how these effects vary based on site characteristics or speed reduction countermeasures that were implemented in coordination with the reduced speed limit.
  4. Based on the findings, develop a summary document to aid Minnesota road agencies in assessing potential speed limit reductions.

Project Details:

  • Estimated Start Date: 06/25/2025
  • Estimated Completion Date: 06/30/2027
  • Funding: MnDOT and Local Road Research Board
  • Principal Investigator: Peter Savolainen
  • Co-Principal Investigators: Tim Gates
  • Technical Liaison: Victor Lund

Details of the research study work plan and timeline are subject to change.

To receive email updates about this project, visit MnDOT’s Office of Research & Innovation to subscribe.

Materials and Construction, research

Evaluating the Use of Stabilizers on Gravel Roads 

Leave a comment

Gravel roads often experience significant deterioration that requires costly maintenance. To mitigate this deterioration, transportation agencies can apply chemical stabilizers to improve aggregate cohesion. This project examined the mechanical, environmental and economic performance of five gravel stabilizers and three application methods to determine the best options for reducing deterioration.

Continue reading Evaluating the Use of Stabilizers on Gravel Roads  →
Environment, research

Protecting Wildlife Along Minnesota Roads

Leave a comment

This week is Wildlife Casualty Count Week of Action in Minnesota. It highlights the impacts transportation systems have on wildlife and raises awareness of wildlife deaths resulting from vehicle collisions. Information about this effort can be found at: Wildlife Casualty Count Week

At MnDOT, we are committed to protecting wildlife through established practices and thoughtful planning. MnDOT works to minimize and mitigate impacts to protected fish, wildlife, and plant species in the design and construction of transportation projects. Read more about MnDOT’s commitment to protected species here: Wildlife – Environmental Stewardship

MnDOT’s Office of Research & Innovation supports research projects that advance wildlife protection and environmental conservation. These projects help inform how wildlife considerations are incorporated into transportation planning and construction. Explore projects guiding this work below:

Goats can play a role in multi-pronged restoration of buckthorn-invaded woodlands | University of Minnesota

Identifying Deer-Vehicle Collision Concentrations in Minnesota

Species From Feces: A New Tool to Identify Bats in Culverts and on Bridges

Assessing a New Tool for Early Detection of Endangered Turtles on Proposed Transportation Projects

Reduce Vehicle-Animal Collisions with Installation of Small Animal Exclusion Fencing

Follow MnDOT’s Office of Research & Innovation to receive the latest updates in transportation research.

Automated Vehicle Technology, research

Rough roads? How everyday cars might help flag trouble spots

Leave a comment

Reprinted from CTS News, May 11, 2026

To assess pavement conditions throughout the state, the Minnesota Department of Transportation (MnDOT) uses a van specially equipped with advanced technology that measures roughness, cracking, and other signs of distress on a roadway’s surface. That system has its limitations, however. The vans cost about $800,000 each, and the data collection requires extensive coordination, trained personnel, and sensitive equipment that is limited to operating in warmer summer months. In addition, the data collection takes place once a year on MnDOT routes and every other year on County State Aid Highways.

van equipped with technology to measure pavement conditions
Mn/DOT’s Pathway Services, Inc. Digital Inspection Vehicle (DIV)

Could there be a more efficient and more timely way to assess the state’s road pavement conditions? To find out, researchers at the University of Minnesota (UMN) explored whether data already being generated by everyday vehicles could enhance MnDOT’s current method. 

To test this, UMN researchers equipped study vehicles with a simple plug-in scanner that captured onboard diagnostics data, explains CTS scholar Raphael Stern, the project’s co-investigator and UMN associate professor of civil, environmental, and geo- engineering. Modern vehicles already have sensors that collect this data, which can be used to monitor and optimize vehicle performance. That same data could provide clues to how a vehicle is responding to pavement beneath it, he says.

“If we could show that this can be done in Minnesota, MnDOT or local agencies can implement this technology,” says lead investigator and CTS scholar Mihai Marasteanu. “They could have a very good idea about the conditions of pavement every day—not just once a year.”

For this project, researchers adapted methodologies from Denmark’s Live Road Assessment (LiRA) project, considered to be the most comprehensive effort to use onboard vehicle sensors for continuous pavement monitoring. That initiative provided insights into both the technical feasibility and practical challenges of extracting meaningful pavement quality metrics from standard vehicle data.

Researchers tested a similar approach on three routes in Minnesota to capture a diverse range of pavement conditions under real-world driving scenarios. One route was a 15-mile loop in the northeast Twin Cities metropolitan area that covered urban and suburban road segments with consistent traffic flow. Another was a 96-mile loop between Minneapolis and Northfield, comprising a mix of urban, suburban, and rural roadways. The third was the 2.6-mile loop at MnROAD, MnDOT’s research facility near Albertville.

The plug-in scanner collected data on vehicle location, speed, and 3D acceleration; the last measures the intensity and complexity of vibrations transmitted from the road through the vehicle’s suspension system.

Across the three routes, researchers collected more than 9,000 data points. Machine learning models used 694 data values to predict pavement quality using the International Roughness Index (IRI) for a given pavement section.

Researchers compared and validated predictions against data from MnDOT and a commercial pavement‑monitoring system. Results demonstrated a correlation across diverse road conditions, although accuracy decreased in areas where pavement conditions changed quickly or road surfaces had defects. Predictions were also more accurate on highway segments than local roads because of variable urban driving environments.

Of the eight learning models evaluated, one achieved 94 percent accuracy on predicting pavement roughness. The performance of each model varied based on environmental factors, data collection conditions, and road types.

The research successfully demonstrated that vehicle sensor data can effectively support continuous infrastructure monitoring, Marasteanu says. “It could save money in the long run and give a much more accurate representation of pavement conditions over the entire year,” he notes.

The project, funded by MnDOT, included implementation guidelines for large-scale deployment, equipment standardization protocols, data-processing pipelines, and risk-mitigation strategies.

MnDOT is now exploring how to extend the research beyond the study vehicles, says Curt Turgeon, director of MnDOT’s Office of Materials and Road Research. One way will be to use commercial data sources that already collect similar information from everyday vehicles. For example, NIRA Dynamics, headquartered in Sweden, partners with automakers Volkswagen and Volvo to collect anonymized sensor data from consumer vehicles. These data streams are captured continuously throughout the year.

“MnDOT has a contract with NIRA to determine how this data might enhance our pavement management decisions as well as potentially document snow and ice response,” he says. “They also have a module that may flag potholes or other in-road hazards based upon vehicles swerving.”

—Peter Raeker, contributing writer

Related reading

Continue reading Rough roads? How everyday cars might help flag trouble spots →