While the end of winter brings warmer temperatures and green grass, it also heralds the beginning of one of the most difficult times of year for drivers: pothole season.
Manik Barman, a professor in the Swenson College of Science and Engineering at the University of Minnesota Duluth and a scholar with the Center for Transportation Studies, discusses what causes potholes, the work that goes into fixing them and how drivers can stay safe on uneven roads.
Q: What causes potholes?
Prof. Barman: Minnesota’s roads endure exceptionally harsh weather conditions. Severely cold temperatures, heavy snowfall, de-icing salt and relentless freeze-thaw cycles significantly influence the state of roads in our region. Potholes are generally a secondary distress symptom following primary structural issues — such as cracks — caused by traffic load, material wear and weather. When water infiltrates the pavement, it expands as it freezes, which creates internal micro-cracks. Once the ice thaws, it leaves behind hollow voids that cannot support weight. Consequently, the load from passing vehicles disintegrates this weakened asphalt, transforming minor flaws into significant potholes.
Q: How are potholes patched?
Prof. Barman: Potholes need to be repaired to ensure the safety of all road users. Different patching methods and materials are available, including conventional asphalt mixes, cold mixes and specialized proprietary materials. Historically, winter potholes were temporarily patched using a cold mix as a stopgap measure until more permanent patching could be applied. Since patching with hot mixes is usually performed in non-winter seasons, crews have often had to visit and repair the same pothole multiple times.
Q: How have repair methods changed?
Prof. Barman: In recent years, innovations have been made in both methods and materials, and the University of Minnesota has been involved with many projects designed to help crews make Minnesota roads safer. Hot mixes are the best to repair potholes, and on-site equipment has advanced so they can be used during winter, too. By heating existing materials around the pothole, hot mixes enhance the bonding of the patch and lead to better long-term conditions. Among these new patching materials, the University of Minnesota Duluth’s taconite-based patching material is fast-setting, lasts significantly longer and can be applied more easily in winter.
Q: What should Minnesotans know about potholes?
Prof. Barman: Transportation agencies work hard to mitigate the hazards of pothole-infested roads through preventive maintenance and periodic repair projects. However, given Minnesota's volatile climate — specifically the relentless freeze-thaw cycle — potholes remain an unavoidable reality of our local infrastructure.
Here are some pothole tips for drivers:
- Anticipate potholes and consider scheduling extra time to drive slowly and cautiously.
- Watch for vehicle damage after pothole encounters.
- Report pothole occurrences to transportation agencies in your city, county and/or MnDOT as soon as possible.
- While frustrating, potholes are a byproduct of the same extreme weather that defines our region. Staying calm and focused ensures you make safer decisions behind the wheel.
Q: How is the University of Minnesota advancing road maintenance techniques and technology?
Prof. Barman: My research is dedicated to the theme of “Better Roads,” focusing on the development of innovative and sustainable pavement materials, designs and maintenance strategies. A key outcome of my research work was a pothole patching guide and decision framework for Minnesota: easy-to-follow flashcards were developed for maintenance crews to select the most effective patching method based on specific pothole characteristics. We also determined the most cost-effective pavement crack sealing method for Minnesota roads so we can decrease moisture infiltration and stay ahead of the freeze-thaw cycles that create potholes. One of my recent projects focuses on mitigating the tenting of asphalt pavement cracks in frigid winter temperatures, which is also a significant factor for pothole formation.
Manik Barman, Ph.D., is a professor in the Swenson College of Science and Engineering at the University of Minnesota Duluth and a scholar with the Center for Transportation Studies. His scholarly focus is on pavement design, rehabilitation and maintenance. He is currently researching pavement rehabilitation and maintenance issues, fiber reinforced concretes for long-lasting pavement rehabilitation and asphalt mixtures for low-volume roads.
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About the Center for Transportation Studies
The Center for Transportation Studies at the University of Minnesota is a national leader in transportation research, engagement and education. CTS collaborates with public-sector, industry and academic partners to shape transportation systems that are sustainable, serve the needs of all users, support a strong economy and improve our collective quality of life. Learn more at cts.umn.edu.
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