Category Archives: Bridges and Structures

Report examines condition of Minnesota’s roads and bridges to inform future investments

Reprinted from CTS News October 6, 2026

From freight, commercial, and public transit to personal commuters, delivery drivers, and emergency services, millions of vehicles travel Minnesota roadways each year. As the number of drivers on the roads grows, ensuring safe and reliable transportation infrastructure is crucial. A recent analysis performed by the Transportation Policy and Economic Competitiveness (TPEC) Program examined the performance and condition of Minnesota’s roadways at the county level from 2018–2024.

Using data regularly collected and maintained by the state, the TPEC team — led by Camila Fonseca-Sarmiento, director of fiscal research at the Institute for Urban and Regional Infrastructure Finance at the UMN’s Humphrey School of Public Affairs and a CTS scholar — assessed condition, safety, and performance trends of Minnesota transportation infrastructure and how these measures have changed over time. Bridge and pavement conditions were categorized as being in good condition, fair condition, or poor condition.

Pavement conditions and trends

The data examined focused on two roadway networks in Minnesota — the National Highway System (NHS) and the County State-Aid Highway (CSAH) system. The NHS, which includes interstates and local and national highways, makes up just 10 percent of statewide lane miles but carries a majority of vehicle traffic. The CSAH system carries significantly less traffic but is more than double the length of the NHS. Pavement types across these roadway networks were evaluated by surface distress or visible defects, ride quality or pavement smoothness, the overall condition of pavement, and the estimated time until the end of the pavement’s service life. Among the analysis’s key insights:

  • More than 80 percent of NHS roads and more than 60 percent of CSAH system roads are in good condition.
  • The CSAH system has more than double the number of roads in poor condition than the NHS.
  • Interstates consistently have the highest pavement quality.
  • Counties with an interstate highway tend to have the most vehicle traffic and pavement in good condition.
  • Counties in northwest Minnesota have the most CSAH roads in good condition while the metro area has the fewest.

Bridge conditions and trends

The team’s research found that the bridge network across Minnesota, comprising 13,500 bridges, remains generally well maintained. Some key trends identified:

  • Bridge conditions have been slowly declining since 2019, with the number of bridges in fair condition increasing.
  • As the population grows, the share of bridges in good condition declines.
  • Counties in northwest Minnesota have a higher rate of bridges in poor condition.

These insights indicate that more bridges will require greater levels of maintenance and preservation efforts in the years to come.

Crash trends

The COVID-19 pandemic altered the driving habits of many — as more people stayed home, fewer vehicles traveled the roads. While the total number of crashes across Minnesota has declined since 2020, the severity of crashes has risen slightly. Among the key crash trends from the report:

  • Minnesota counties average 929 crashes per 100,000 people.
  • Counties in southwest Minnesota have higher rates of property damage, injury, and fatal crashes.
  • Counties in northwest Minnesota have lower rates of property damage, injury, and fatal crashes.
  • Between 2019 and 2023, crashes statewide causing property damage decreased by 22 percent and fatal and injury crashes decreased by 13 percent.
  • Severe weather or wildlife encounters may be contributing to increased crashes in some counties.
  • As the population grows, crash rates increase.
Minnesota county map shaded by rates per 100,000, ranging from 0–500 to 1501+, with some areas marked NA

“The findings emphasize the importance of continued monitoring and investment in Minnesota’s transportation infrastructure,” Fonseca-Sarmiento says. “Understanding how roadway and bridge conditions vary throughout the state is essential for prioritizing resources when investing in the transportation network and improving safety. As transportation demands continue to evolve, data-driven decision-making will remain crucial to ensure a reliable and resilient transportation network for Minnesotans.”

— Krysta Rzeszutek, CTS digital editor

Related MnDOT Research from 2026

Evaluating a New Low Slump Concrete for Bridge Decks 

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  →

CTS Webinar: Infrastructure Materials and Performance

Tuesday, April 21, 2026
noon–1:30 p.m. CDT, Virtual

About the Event

Understanding how infrastructure materials perform over time is critical to making informed design, construction, and maintenance decisions. This webinar will feature two recent University of Minnesota research efforts that examined the real-world performance of commonly used transportation infrastructure materials.

Continue reading CTS Webinar: Infrastructure Materials and Performance →

Strategies to Prevent Joint Separations in Culverts

Culverts are essential components of urban and rural infrastructure that guide and channel water under roads and embankments. The most common failure affecting culverts is joint separation between segments of the concrete pipes. This project examined the predictors and factors that lead to joint separations in culverts to determine practices that will decrease future separations.

Continue reading Strategies to Prevent Joint Separations in Culverts →

CTS Webinar: Species from Feces—A New Tool to Identify Bats in Culverts and on Bridges

Wednesday, April 22, 2026, 12:00–1:30 pm, Virtual

About the Webinar

Bats frequently use bridges and culverts as roosting habitat, creating challenges for transportation agencies working to balance infrastructure needs with environmental compliance. Traditional visual surveys can be limited, especially when bats are hidden within structures or present only intermittently. 

This webinar will highlight ongoing research exploring the use of DNA analysis from bat feces (guano) as a noninvasive method to identify bat species occupying culverts and bridges. Speaker Ron Moen will discuss how this approach works, share early findings from field applications, and explore how the results could support more efficient environmental review, project planning, and species protection efforts for transportation agencies.

It is being held in conjunction with a CTS Environment and Energy in Transportation Council meeting.

Speaker

Ron Moen is an associate professor in the Department of Biology at the University of Minnesota Duluth and a senior research associate with the Natural Resources Research Institute’s Center for Water and the Environment. His research focuses on mammalian ecology, including habitat use, movement patterns, and predator–prey interactions, often using GPS radiotelemetry. His current work includes studies on moose, Canada lynx, American marten, wood turtles, bats, and other wildlife, as well as projects related to climate change impacts and carnivore monitoring in the Upper Midwest.

Registration

This webinar is free, but registration is required. Once you have registered, you will receive an email confirmation with a Zoom link. The link should not be shared with others; it is unique to you.

Follow the Research

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

Evaluating Strategies to Prevent Early-Age Bridge Deck Cracking  

Premature cracking in reinforced concrete bridge decks is expensive to repair and may lead to rapid bridge deterioration. Despite changes to mix designs, transverse cracking after casting continues to be a problem in Minnesota. This project evaluated alternative concrete mix designs and reinforcement strategies to mitigate early-age bridge deck cracking, reduce maintenance costs and extend bridge deck service lives.

Continue reading Evaluating Strategies to Prevent Early-Age Bridge Deck Cracking   →

Repairing In-Water Bridge Supports Using Innovative Methods and Materials

In recent years, advancements in bridge repair techniques and technologies promise to offer more options for strengthening an existing bridge’s in-water piles, eliminating the need to reroute both water and traffic. This project investigated other states’ experiences with several products on the market and provided an opportunity for Minnesota’s engineers to evaluate two vendors’ systems on a bridge in need of restoration. 

Continue reading Repairing In-Water Bridge Supports Using Innovative Methods and Materials →

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

Three bat species in Minnesota have been decimated due to white-nose syndrome. The northern long-eared bat is listed as endangered by the U.S. Fish and Wildlife Service, the tricolored bat listing is imminent, and the little brown bat listing is under consideration.

Continue reading New Project: Species from Feces: A New Tool to Identify Bats in Culverts and on Bridges →

New Project: Develop Element Level Bridge Performance Measures and Targets

Currently, federal bridge performance measures in the United States and measures most commonly used by state transportation agencies for bridge management are based on National Bridge Inventory (NBI) General Condition Ratings that reflect bridge component conditions (deck, superstructure and substructure).

MnDOT also collects bridge element data that provides a more granular, objective and quantitative assessment of condition, and would like to have performance measures and targets based on the bridge element data that guides a data-driven methodology to select cost-effective treatments.

Continue reading New Project: Develop Element Level Bridge Performance Measures and Targets →

Assessment of GFRP-Reinforced Bridge Deck Performance

A nonmetallic alternative to the steel rebars that reinforce concrete bridge decks has the potential to be longer lasting and more cost-effective in keeping bridges maintained in Minnesota’s harsh climate. Initial studies show that the performance of bridge decks built with glass fiber-reinforced polymer (GFRP) is comparable to—if not better than—conventionally built decks.

Continue reading Assessment of GFRP-Reinforced Bridge Deck Performance →