New bridge repair method offers promising results





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Transportation Research Update
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BRIDGES AND STRUCTURES

Repairing In-Water Bridge Supports Using Innovative Methods and Materials [ [link removed] ]

Man in boat making bridge repairs

Structural repairs to a bridge that has supportive elements in a river, lake or other body of water can mean high costs and substantial disruption to the environment and area traffic. To remove the water and prepare the site for repairs, engineers would typically build a temporary wall and run pumps to keep the area dry for the duration of the project. The bridge’s deck might also be removed for easier access, and boat and vehicle traffic might be rerouted until the work is completed.

In recent years, innovative construction materials and methods have been developed to offer a potentially faster and easier solution for repairing a bridge’s piles without removing the surrounding water. After learning of other states’ successes with these proprietary bridge pile repair systems, MnDOT and LRRB partnered on a demonstration project in Minnesota to compare two vendors’ systems on a bridge near St. Cloud. Both systems provided viable results, giving engineers in the state a new option to consider when repairing in-water bridge supports.



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TRAFFIC AND SAFETY

Assessing Reliability and Resilience on Freeway Corridors [ [link removed] ]

Traffic jam on metro freeway

The Twin Cities freeways struggle with traffic congestion and delays when on- and off-ramps are not spaced effectively. Poor placement creates geometric friction, with cars weaving among lanes as they enter and exit the freeway. Understanding the effects of geometric friction can assist MnDOT in future planning efforts to reduce congestion and increase travel-time reliability.

Freeway corridors and networks are susceptible to variations in travel times and performance. Increasing the resilience—the ability to withstand disturbances such as accidents and poor weather—of the freeway corridors and network is an important aspect of maintaining a high level of service. MnDOT used a Travel-Time Reliability Estimation System and resilience model with weather-related data to evaluate individual and corridor-wide operational resilience. The results indicated lower reliability and resilience in freeway segments with higher geometric friction.



Examining Driver Preferences for Lane Line Patterns and Widths [ [link removed] ]

Stretch of highway showing different road markings

MnDOT research has indicated the need to change the dimensions of lane markings on highways in Minnesota. In a recent study, drivers indicated a preference to increase the width of white lane markings from 4 inches to 6 inches and to extend their length from 10 feet to 12.5 feet. Making these changes along with using black contrasting markings to highlight the white lane markings could lead to fewer crashes and safer driving in Minnesota.

In this project, 56 licensed drivers rated different pavement markings on a test route based on visibility and preference. Additionally, drivers completed a post-test survey further indicating their preferences for the width and length of white pavement markings along with the spacing between them. Test results also evaluated technology used by automated vehicles to recognize the pavement markings.



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MATERIALS AND CONSTRUCTION

An Innovative Practical Approach to Assessing Bitumen Compatibility as an End Means of Material Specification [ [link removed] ]

pavement fiber

Modern asphalt mixtures are usually a combination of various materials from different sources, including reclaimed asphalt pavement (RAP) and recycling agents (RAs), but the lack of a well-established method for determining compatibility between various materials and types of binder has been a major impediment in current asphalt material selection and specification.

The objective of this study was to evaluate various binder and mixture testing methods to characterize the compatibility between complex components of asphalt mixtures, specifically from the perspective of assessing their cracking performance. The study found that rheological characterization of asphalt binder and mixture using the dynamic shear rheometer may not adequately capture the incompatibility between virgin binder, RAP, and RAs. However, thermal analysis using the differential scanning calorimeter, and mixture fracture tests have shown promising results for evaluating the compatibility of various mixture components. Findings suggest that this may be the best method for agencies to use to select the most compatible component materials from various sources for their projects.



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MULTIMODAL

Increasing Service Reliability by Adding a Dedicated Right of Way for Buses [ [link removed] ]

Bus on red-painted dedicated route

MnDOT research has developed a modeling tool that identifies the bus route segments that would benefit most from the installation of a dedicated right of way (ROW) for buses. Transit service reliability is one of the most requested service improvements. By implementing a transit ROW where needed most, MnDOT can improve transit reliability and better serve riders who use transit to commute to work, complete errands and engage with the community.

This project analyzed bus route reliability and contributing factors, such as traffic lights and traffic volume, to better understand where low reliability service occurs and if an ROW would be beneficial. Test results indicated that an increased ratio of bus lanes and busways led to more reliability, but only when the ratio exceeds 20%. Other factors associated with more reliable transit service are higher free-flow speeds, fewer traffic signals and longer route segments. Additional analyses identified specific route segments along several service corridors that would benefit most from an ROW.



Modeling and Predicting the Deterioration of Pedestrian Assets [ [link removed] ]

Pedestrians on sidewalk

MnDOT research has developed a modeling framework to predict the deterioration stages of pedestrian assets. Using this framework, pedestrian infrastructure managers can better determine which assets, such as sidewalks or pedestrian bridges, need to be repaired most urgently. Prioritizing pedestrian asset maintenance, repair and replacement will lead to construction savings, lower life cycle costs, safer pedestrian use and higher accessibility compliance.

This project created a comprehensive pedestrian asset dataset that integrated intricate and expansive historical data from MnDOT detailing pedestrian access routes, land use data and climate data. Using this data, researchers developed a framework for modeling the deterioration of pedestrian infrastructure. The results demonstrated that the model could be used to inform and assist decision-making for pedestrian asset management, allocating resources and determining maintenance schedules.



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UPCOMING EVENTS

*MnDOT webinars*

*April 9, 2025, School Times Impacts on Students Walking or Biking to School [ [link removed] ]
*Join us for a webinar on April 9 from 2-3 p.m. on how school start times influence in student’s decision to walk and bike to school. Led by MnDOT’s Safe Routes to School (MnSRTS) Program, this webinar will share research findings, policy considerations, and strategies to make active transportation a safe, convenient, and confident choice for all students. Safe Routes to School programs improve safety, reduce traffic and improve air quality near schools through a multidisciplinary approach that is structured around evaluation, education, encouragement, equity, engagement, and engineering.

*April 17, 2025,* Research Radar: *Environmental Innovations [ [link removed] ]
*Join us on April 17 from 10-11 a.m. for a webinar on Environmental Innovations. This webinar will feature: Identifying Deer-Vehicle Collision Concentrations in Minnesota, [ [link removed] ]Species From Feces: A New Tool to Identify Bats in Culverts and on Bridges, [ [link removed] ]Assessing a New Tool for Early Detection of Endangered Turtles on Proposed Transportation Projects [ [link removed] ]

Other events

* *April 4, 2025*, CTS Webinar: Innovative Soil Solutions for Sustainable Design [ [link removed] ]
* *April 25, 2025, *CTS Webinar: Effect of Tree Shade on Winter Maintenance Operations [ [link removed] ]
* *April 30, 2025, *CTS Webinar: Pedestrian Safety and Driver Behavior Near an Automated Vehicle [ [link removed] ]
* *Aug. 5, 2025, **2025 Salt Symposium [ [link removed] ] *
* *Aug. 25 to 27, 2025*, 2025 MAASTO Annual Conference [ [link removed] ]
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