Life cycle assessments and Environmental Product Declarations (EPDs) help transportation agencies measure and reduce greenhouse gas emissions from infrastructure projects. This study examined how these tools can assess emissions from asphalt transportation and paving operations. Findings showed that construction activities can be a major source of emissions, especially when projects require thicker pavement layers or involve long hauling distances. Emissions were lower for projects with faster paving speeds, higher production rates, and portable asphalt plants located close to the work site. To support broader implementation, investigators also created a web-based system to streamline the submission, storage, and management of EPD data, enabling MnDOT to more efficiently integrate environmental considerations into procurement and project planning.

Low slump concrete overlays are an effective way to extend the life of bridge decks, but MnDOT’s current low slump mixture has begun showing extensive cracking after installation, prompting the agency to seek a revised mixture that reduces cracking while still achieving low permeability and a minimum compressive strength of 4,000 psi. MnDOT evaluated a new low slump concrete mixture, both with and without glass fibers, alongside the existing mix, and found that each version of the new mixture provided adequate strength and electrical resistivity. Although the fiber‑reinforced option costs more and requires slightly more finishing effort, it significantly reduces crack sizes by about 50%, improving toughness and potentially extending service life.

Research consistently shows that roundabouts and J-turns offer notable safety and traffic flow benefits, yet MnDOT and local agencies often face scrutiny from business and community stakeholders who worry that changes in traffic patterns or driver behavior could harm nearby businesses. This multi‑step research effort confirmed that roundabouts and J-turns continue to deliver positive outcomes by documenting supportive public and stakeholder perceptions, improved traffic operations, and substantial safety benefits. Investigators also analyzed revenue trends for businesses within a half-mile of these intersections across Minnesota and found no negative economic impacts. To further support adoption, the project produced a public education video that MnDOT and local governments can use when planning and implementing future roundabouts and J-turns.

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.

High vehicle speeds significantly increase the likelihood of fatal and serious injury crashes. To support efforts to improve safety on lower-volume urban roads, this project examined how centerlines and edgelines affect vehicle speeds and lateral positioning.

Results showed that vehicles traveled more slowly and farther from the opposing traffic lane when centerlines and edgelines were not present. Drivers also provided significantly more lateral space to parked vehicles and shoulder bicyclists when no centerline was present. Based on these findings, centerlines should be optional on relatively straight two-lane urban streets with speed limits below 35 mph, widths greater than 20 feet and average annual daily traffic volumes below 6,000.

The MnDOT Library was filled with creativity and collaboration on Aug. 19 as MnDOT’s Innovation Community of Practice hosted a hands-on demonstration of MnDOT’s Complete Streets engagement kits. About 40 participants –from MnDOT and external partners including Bolton & Menk, the Metropolitan Council, SRF, HR Green, Goodhue County, SPPM and streets.mn explored how the kits improve engagement and bring street design ideas to life. Nissa Tupper, with MnDOT’s Office of Sustainability and Public Health and creator of the kits, guided attendees through the Complete Streets approach while explaining the origins and practical features that make the kits a versatile planning tool. Participants experienced how the kits make street design more visual, accessible and interactive by helping communities easily “see and feel” different options. The kits are available in every MnDOT district and can be used for freestyle brainstorming or structured gameplay, making them well suited for tabling events, workshops, trainings and project open houses.

The following research was referenced in the development of the kits:

• Complete Streets from Policy to Project Guidebook
• How do Complete Streets Matter for Communities? The Case of Richfield, MN 
• Assessing the Economic Effects of Context Sensitive Main Street Highways in Small Cities

Thursday, September 17, 10:00-11:15 a.m.

Join MnDOT's Office of Research and Innovation and the MN Local Road Research Board for this month's Research Radar: Bridge Maintenance. Come learn about new and innovative research that helps extend the life of Minnesota's bridges and support long-term, sustainable maintenance.

MnDOT is joining the national Week Without Driving campaign onOct. 1 – 8. This challenge encourages us to experience daily travel without driving – whether by walking, biking, rolling, using public transit, or asking for rides from family or friends.

MnDOT staff are participating because, as transportation professionals who influence plan, design, engineer, construct, and maintain the transportation system for all modes, it is important to understand the experience of Minnesotans who cannot drive (whether permanently or temporarily) and rely on transit, walking/rolling, biking, or catching rides.

We invite you to participate in a way that fits your life. Pledge for the entire week, pledge not to drive yourself for part of the week or learn more about travel options in your area and barriers nondrivers experience.

MnDOT is hosting the following webinars to build awareness of the campaign:

• MnDOT Week Without Driving webinar series: When Driving is Not an Option – Disussion with author, Anna Zivarts (register via link), September 21, virtual (stop by the MnDOT Library and check out a copy of Zivarts’ book!)
• MnDOT Week Without Driving webinar series: Getting Back into Biking (join via link), September 29, virtual