Category Archives: research

General research posts.

Materials and Construction, research

New Project: Holistic design and selection criteria for unbound geomaterials used in pavement systems

Leave a comment

Unbound geomaterials used in roadway base layers strongly influence pavement durability, yet current practices in Minnesota often focus narrowly on gradation and index properties. This research seeks to fill that gap by examining mechanical behavior alongside hydraulic, water retention, and suction characteristics to better understand how these materials perform within real-world environmental and pavement systems.

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

Pavement base layers serve two essential purposes: providing mechanical support that prevents fatigue, settlement, and rutting, and enabling drainage that protects the structure from elevated pore pressures and freeze‑thaw damage. Although millions of tons of these materials are used annually, past studies rarely consider the full interaction between the base layer, surface conditions, and environmental factors.

The project’s primary goal is to develop a new holistic guideline for selecting unbound geomaterials and designing pavement foundations. By integrating both mechanistic and hydraulic considerations, the long‑term objective is to support a shift toward design approaches that enhance roadway performance while reducing maintenance needs and costs.

The Objectives:

This project aims to develop a new holistic unbound geomaterial selection and pavement foundation design guideline. This will be achieved through the completion of four primary objectives:

  1. Review of current roadway foundation design practices and guidelines of MnDOT and local counties and cities in Minnesota.
  2. Collection and analysis of existing data from the literature on the topic (including the extensive previous work of the research team).
  3. Developing a holistic design and material selection framework that explicitly takes material drainage characteristics, material mechanical characteristics, unsaturated soil mechanics properties, and prevailing environmental characteristics into account.
  4. Extensive laboratory and field testing to demonstrate and verify the new approach.
  5. Evaluating and modifying the pore suction resistance factors and seasonal multipliers used in MnPAVE.

Project Details:

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.

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.

research

Innovation at work: Minnesota Mousetrap award winners

Leave a comment

Originally published by the Center for Transportation Studies, July 6, 20205 as Minnesota Mousetrap award winners: Crack Wagon De-Tack Sprayer and Curb Stop Wrench Truck Storage Solution | Minnesota LTAP

Congratulations to the recipients of Minnesota’s 2026 Build a Better Mousetrap awards! All Minnesota submissions were forwarded to the national mousetrap program in June. Awardees from across the country will be chosen by the National LTAP & TTAP Association in four categories.

Minnesota Pioneer Award

The City of St. Cloud’s Crack Wagon De-Tack Sprayer was recognized with the Minnesota Pioneer Award, given to a locally relevant product or tool that is among the first to solve a maintenance problem with a homegrown solution.

Problem: Spraying crack filler typically requires the work of multiple laborers and creates an unsightly mess of toilet paper, which is used for absorbing the sticky residue.

Solution: For $360, City of St. Cloud staff members created a 25-gallon flat-bottom tank that holds water and Dawn dish soap, complete with an attached hose and wand that can be used by one person to apply the solution. This eliminates the need for a follow truck to spray soapy water over the cracks, reducing the number of laborers on the road and amount of toilet paper clean-up. It’s an environmentally friendly solution that benefits both workers and residents.

SMART Transformation Award

The City of Waite Park received the SMART Transformation Award for its Curb Stop Wrench Truck Storage Solution. This recognition is awarded for a locally relevant significant change to any transportation activity or process that is SMART (Specific, Measurable, Achievable, Realistic, and Time-bound) and results in improved efficiencies. 

Problem: City of Waite Park staff members prefer to use crew cab pickup trucks for their work because of the interior storage capacity. But there’s an issue: longer truck cabs mean shorter beds. When storing and transporting materials such as curb stop wrenches, which are around 10 feet long, creative solutions are required.

Solution: The agency constructed a storage apparatus and installed it onto a ladder rack that sits above the truck bed. The device consists of exhaust tubing secured to front and rear plates with u-bolts and is equipped with a locking mechanism built from common gate hardware. The wrenches slide right into the tubes and are secured for transport — a convenient storage solution for just $175.

Honorable mention: City of St. Paul’s Improved No Parking Stake

Problem: City of St. Paul workers were frequently injured while hammering wooden “No Parking” signs into the ground.

Solution: By affixing a metal spike to the bottom of each sign, the signs can easily be pushed into the ground, removing the hazard of hammering entirely. This solution also decreases the sign installation time — an added bonus for staff members.

Learn more about award-winning projects from previous years.

The Minnesota Build a Better Mousetrap Competition is sponsored by the Minnesota Local Road Research Board and administered by MnLTAP.

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  →
Multi-modal, Policy and Planning, research

Integrating travel demand management into transportation planning

Leave a comment

Reprinted from Catalyst, June 22, 2026

Minnesota’s transportation landscape is rich with options designed to get travelers to their destinations safely and quickly. These modes, ranging from commuter bike trails and public transit to rideshares, buses, rail, roads, streets, and highways, are strategically interlinked; improvements or disruptions in one place reverberate across the greater transportation network.

Travel demand management (TDM) is an approach to transportation planning that encourages more efficient travel through a combination of mode choice and infrastructure design. This “big picture” approach centers the specific needs of local communities to create viable options for people to shift away from single-occupancy vehicles for at least some trips. Among the benefits of more efficient road use are improved congestion and air quality and reduced costs for road maintenance and construction.

A UMN research study led by Kaitlyn Denten, infrastructure policy researcher at the Institute for Urban and Regional Infrastructure Finance within the Humphrey School of Public Affairs and a CTS scholar, aimed to investigate how TDM strategies can best be integrated into highway construction projects.

In Minnesota, two factors are bringing the TDM approach to the forefront. The Transportation Greenhouse Gas Emissions Impact Assessment (Minn. Stat. §161.178 [2025]) is now part of highway construction and reconstruction projects. This statute requires projects to meet state greenhouse gas (GHG) and vehicle miles traveled (VMT) goals by either modifying the project, halting the project, or offsetting the GHG and VMT created by the project. 

Additionally, the Metropolitan Council, through its 2023 Regional Travel Demand Management Study Action Plan, recommended that a study be conducted to identify how TDM strategies could be incorporated into all phases of highway construction. The Met Council’s goal is to improve commuting, meet climate objectives, and reduce or delay the need for costly highway expansion projects.

In response to the Met Council’s recommendation, the UMN research team first conducted a nationwide scan to identify best practices for integrating TDM into highway projects. Examples in Colorado, California, New Jersey, Delaware, and Washington show how local, state, and federal transportation agencies and other entities coordinated to better understand local travel patterns and solve complex challenges. The scan revealed how TDM has been used to inform planning and policy, improve design and construction, encourage mode choice, and manage demand or emergency situations.

The researchers also studied Minnesota examples. The 2007 collapse of the I-35W Bridge in Minneapolis diverted 140,000 daily commuter trips. MnDOT, the Met Council, and regional stakeholders created travel alternatives from the time just after the collapse through the bridge’s reconstruction, which was completed in September 2008. TDM strategies included new transit services, fare subsidization, teleworking programs, and expanded park-and ride facilities.

In Duluth, a more northern expanse of Interstate 35W became a “mega project” between 2010 and 2012. During this time, 3 bridges and 12 miles of roadway pavement were replaced, shoulders and safety features were added, and intelligent transportation systems components were installed for emergency communications. TDM strategies helped facilitate communications between local and state entities, transit services, and the MnDOT construction teams to improve travel alternatives and ease the flow of traffic during this prolonged disruption.

TDM is becoming a more defined and important part of future transportation planning. “Ultimately, integrating TDM into highway projects enhances travel options and creates modal choices for travelers,” Denten says. “This reduces delay during peak times and improves safety and efficiency for construction crews. It can also remove the need for travel and push travel to non-peak times. Further, holistic TDM approaches for highway construction projects could lead to more efficient transportation systems and perhaps delay or remove the need for a highway project in the first place.”

The study offers best practices to help policymakers, planners, engineers, and local officials within the Metropolitan Council and beyond incorporate TDM into their projects. These strategies provide opportunities to shape policies and projects that respond to unexpected and intermittent challenges while supporting Minnesota’s long-term goals of reducing highway construction costs, climate impacts, and travel disruptions.

This research project was sponsored by the Applied Research in Transportation (ART) Program, which addresses time-sensitive research questions in a 6- to 12-month timeframe. CTS and the Minnesota Department of Transportation contributed initial funding to launch this pilot program in 2024, with the Metropolitan Council joining in 2025. To reinforce the applied nature of the program, ART projects must directly address a current process, document, or policy need with an initial focus on sustainability in transportation and climate change impacts. 

—Amy Goetzman, contributing writer

Environment, research

Reducing Phosphorus Pollution from Ponds

Leave a comment

Ponds and historic wetlands are essential for preventing excessive phosphorus from reaching downstream waters. These systems remove solids, nutrients, metals and hydrocarbons from stormwater runoff as particles settle to the bottom. However, low oxygen levels in the water can cause phosphorous to be released from bottom sediments. This project examined the effectiveness of strategies to limit that release and reduce negative downstream impacts.

Continue reading Reducing Phosphorus Pollution from Ponds →
Materials and Construction, research

New Project: Are Current Rigid Pavement Roundabout Designs Working in Minnesota?

Leave a comment

As roundabouts become more commonplace in Minnesota, the role they play in the improvement of traffic flow and safety increases. Although rigid roundabouts were originally designed with the assumption that they would behave like rigid pavements on motorways, their performance can be affected by the unique traffic patterns and stresses they experience. The irregular shapes of their concrete slabs face distinct braking, stopping, accelerating, and drainage conditions, which increase the likelihood of cracking and other forms of pavement distress. Heavy trucks navigating sharp curves add additional strain. While concrete pavements are generally durable, pavement wear is greatly affected by elements characteristic of roundabout design.

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

This research seeks to evaluate and improve the performance of concrete roundabouts in Minnesota, with the aim of extending their service life and increasing their overall effectiveness. The project will start with a comprehensive field survey throughout the state, collecting information on different roundabout designs and documenting the types and levels of pavement distress present. The data will be analyzed to identify performance trends and gain a clear understanding of each design’s advantages and shortcomings. In addition to the field investigation, the study will conduct an in-depth structural review of factors such as joint spacing, dowel bar placement, slab geometry, and drainage features.

Using insights from both the field observations and structural analysis, researchers will propose design strategies to improve the durability of Minnesota’s roundabouts. These recommendations have the potential to strengthen roundabout design practices and contribute to a safer, more dependable transportation system.

“With the rapidly growing number of concrete roundabouts being constructed throughout Minnesota, it is important that we monitor their performance and adjust our design methodologies to ensure that the traveling public can utilize them safely, while maximizing the investments spent on their construction and maintenance,” said Thomas Burnham, research operations engineer with MnDOT’s Office of Materials and Road Research. “This research project is set up to accomplish these goals.”

The Objectives:

  1. To measure rigid pavement roundabout performance for various traffic loads and design features.
  2. Using pavement system performance data, identify any design changes that could minimize maintenance.
  3. Create state-of-the-art guidelines and recommendations for improving the design, function and lifespan of concrete roundabouts in Minnesota.

Project Details:

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

Exploring the Factors Driving Vitality in Transportation Corridors: Lessons from Minnesota

Leave a comment

Thursday, July 16, 2026, 10:00 am–2:00 pm

In Person

Bell Museum
The Nucleus Conference Room
2088 Larpenteur Avenue West
Saint Paul, MN 55113

About the Event

In a follow up to a March webinar, Economic Impacts of Freeway Corridors, this in-person event will share preliminary findings from an ongoing MnDOT research project studying the economic impacts of freeway corridors. There are many discussions about rethinking freeway corridor designs in Minnesota and nationally. Economic impacts should be considered when selecting a design alternative, but these are difficult to quantify. This research aims to provide a framework to better estimate the impacts of freeway corridor alternative projects by also considering mode, scale, land uses, community engagement practices, and environmental impacts.

Sponsored by the Institute for Urban and Regional Infrastructure Finance (IURIF) at the Humphrey School of Public Affairs, this event will focus on community engagement around infrastructure transformation. Presenters will discuss the intersection of 38th and Chicago in Minneapolis and share insights about how MnDOT approaches engagement for projects in Northeast Minnesota. In addition, IURIF researchers will lead an open discussion of each facet of the research around the economic impacts of freeway corridors, including community engagement, land use, environmental aspects, and socioeconomic impacts.

Speakers

Alexander Kado is a senior project manager with the City of Minneapolis Office of Public Service, where he oversees critical infrastructure investments shaped by community voice. He is currently directing two legacy projects of immense civic significance: the redevelopment of George Floyd Square and the creation of the Minneapolis Democracy Center — a transformation of the former Third Precinct building into a space for civic participation. Guided by a commitment to equitable urban outcomes, Alexander bridges technical precision with social advocacy. He holds a master’s degree in city and regional planning from the University of North Carolina – Chapel Hill and a BS in mechanical engineering from the University of Minnesota Twin Cities.

Duane Hill is a 1988 graduate of North Dakota State University with a BS in civil engineering. He has more than 38 years of engineering experience, mostly in the transportation field with the Minnesota Department of Transportation. Duane’s experience includes highway design, project management, environmental, construction engineering, bridge engineering and field operations management. Duane has been the district engineer in MnDOT District One since March 2012.

Registration

The event is free, but registration is required.

Register