Research Reports

This report presents the findings of a research study to identify transferrable lessons from behavior-change and culture-building models that could help inform state efforts to reduce vehicle miles traveled (VMT) by 20 percent by 2050. It includes a literature review of academic and public agency documents as well as interviews and focus groups. This project demonstrates that the similarities between transportation- and non-transportation-focused behavior-change methods can provide important lessons for application of strategies to support the reduction of VMT in Minnesota, providing MnDOT and partners across the state many opportunities to achieve reductions in VMT.

This Research Summary is part of the final deliverable for Report 2025-21, "School start times impact on students walking or biking to school: Safe routes to school."

Some school districts schedule elementary schools with early start times for various reasons. Such start times sometimes necessitate travel before sunrise during winter months. Intuitively, this could potentially conflict with a desire for increased use of active transportation, e.g. from the Safe Routes To School program, to reduce motor vehicle travel and associated traffic congestion from driving students to school. Since prior literature has identified that parents are concerned about child safety around traffic, it is possible that travel before sunrise (where visibility is reduced) would also be a concern to parents and further discourage active transportation. To answer this question, we conducted a stated preference survey of parents about their child's travel choices, asking parents to rank the importance of various factors including travel before sunrise. Due to concerns about whether stated parental preferences would align with actual behavior, we also conducted a revealed preference survey using StreetLight data on travel to elementary schools. Survey distribution and data collection occurred in February in Minnesota, during a period of late sunrise. Overall, the results from all data analyses are aligned. Early school start times were associated with slightly higher use of active transportation in both stated and revealed travel patterns. Parents ranked travel before sunrise only as a moderate concern behind distance, infrastructure, crossing busy roads, and child's age. We did not find data to conclude that travel before sunrise significantly limits use of active transportation.

Asphalt rejuvenators, or recycling agents (RA), are used to incorporate higher amounts of Reclaimed Asphalt Pavement (RAP) in Hot Mix Asphalt (HMA) without detrimentally impacting the long-term performance of the pavement. The National Road Research Alliance (NRRA) Flexible Team constructed field test sections as part of a mill and overlay project in northern Minnesota in August of 2019. These field sections included wearing courses with 40% RAP that incorporate seven different RA products, with the dosage determined by the supplier to meet a target extracted and recovered performance grade (PG) of XX-34. In addition to the RA test sections, there were control sections with 40% RAP and 30% RAP (the maximum level allowed on the remainder of this project). The objective of this research project was to evaluate the effectiveness of the seven RA products over time and evaluate their performance as compared to the control mixtures. This was accomplished through a combination of binder (chemical and rheological) and mixture characterization and performance testing using different laboratory aging levels, field core testing, and performance monitoring of the field sections over time. This report documents the results after four years in service with cores taken annually. The study showed that all RAs exhibit improved rheological properties in 1-year field cores. However, the benefits of RA diminish with field aging, and after four years, some RAs show comparable properties with controls. In terms of mixture properties, the inclusion of RA enhances both rheological properties and fracture and fatigue crack resistance initially.

This research summary is part of the final deliverable for Report 2025-22, "Comparison of Compost and Proprietary Soil Amendments for Vegetation Establishment," Published in March 2025.

Post-construction roadside soils often suffer from compaction, low fertility, and poor structure, challenging vegetation establishment and stormwater management. This study evaluates the effectiveness of organic amendments (OAs) and proprietary amendments as alternatives to traditional methods. The study involves greenhouse experiments (pot and mesocosm) and field experiments to evaluate vegetation growth and water quality across different amendment and soil applications. Results show that compost amendments significantly improve vegetation growth, with yard-waste compost outperforming others. Biochar shows early growth potential but requires nutrient supplementation for sustained performance. Proprietary amendments support rapid vegetation establishment, enhanced root density, and reduced nutrient leaching, with Sustane 4-6-4 exhibiting consistent growth across application rates. The field study validates greenhouse findings and shows increased biomass and root density with compost amendments, while proprietary amendments result in high nutrient retention and runoff quality. This study highlights the potential use of OAs and PAs to reduce erosion and support long-term vegetation growth. The findings provide practical guidelines, benefits and implementation steps for managing roadside soils after construction activities.

Connected and automated vehicle (CAV) technology has the potential to significantly increase work zone safety. Each day, MnDOT maintenance employees and contractors are at risk of being involved in crashes when performing road work. To mitigate this risk, MnDOT uses truck mounted attenuators – or crash cushions – to help protect roadside workers)

This research summary is part of the final deliverable for Report 2025-19, "Assessing the Deterioration of Pedestrian Assets," published in February 2025,

This research summary is part of the final deliverable for Report 2025-01, "Value of Dedicated Right-of-Way: Transit Service Reliability and User Impacts," published in February 2025.

Transit services connect people to jobs and opportunities, fostering vibrant communities and multimodal travel along service corridors. A transit right-of-way (ROW) can help buses bypass congestion and stay on schedule. Many studies have proved that transit ROWs effectively improve service reliability and reduce user costs. However, these studies often focus on one or two service corridors, limiting comprehensive impact assessment. This project addresses this gap by investigating service reliability for all route segments across a transit system. We derived reliability metrics at the route segment level using high-resolution automatic vehicle location (AVL) and automatic passenger count (APC) data collected in the Twin Cities metropolitan area. We then collected and integrated data from various sources via spatial-temporal computing to capture service characteristics, operating environments, traffic conditions, and land-use features along route segments. We applied the Gradient Boosting Model (GBM) to examine nonlinear relationships between these factors and bus travel time reliability. Lastly, we used the trained model to estimate potential improvements in reliability with dedicated ROWs. Through these steps, we worked with members of the Technical Advisory Panel (TAP) to illustrate our methodology and demonstrate its utility for transit agencies. Specifically, the results proved that the ratio of bus lanes and busways was associated with more reliable travel time along route segments. We also found that route segments along a few service corridors with unreliable services can greatly benefit from implementing a dedicated ROW.