Reports

Modern asphalt mixtures are usually a combination of various materials from different sources, including reclaimed asphalt pavement (RAP) and recycling agents (RAs), and are used to attain sustainable growth. However, the lack of a well-established method for determining compatibility between various sources and types of virgin binder, aged binder within RAP, and RAs has been a major impediment in current asphalt material selection and specification. Therefore, 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 primary evaluation consisted of laboratory-prepared materials that used three RAP sources, three asphalt binders (one PG 58–28, two PG 64–22), and two RAs (petroleum-based and bio-oil-based) for both binder and mixture characterization. The binder tests consisted of rheological characterization using the dynamic shear rheometer (DSR) and thermal analysis using the differential scanning calorimeter (DSC), whereas the mixture tests included complex modulus (E*), semi-circular bend (SCB), and disk-shaped compact tension (DCT) tests. The results indicated that the rheological characterization of asphalt binder and mixture may not adequately capture the incompatibility between virgin binder, RAP, and Ras. However, binder DSC analysis and mixture fracture tests have shown promising results for evaluating the compatibility of various mixture components. Therefore, the findings of this study provide agencies with a framework to select the most compatible component materials from various sources for their projects.

This study explored the feasibility and acceptability of using stay in-place fiberglass reinforced plastic (FRP) jackets and underwater steel reinforced grout for timely bridge piling repairs in Minnesota without dewatering. One of the goals of the project was to determine the current state of practice to this corrosion repair and inspection by researching other projects using similar repairs and to develop a survey to other departments of transportation to gather their experience with this type of repair. Another goal was to document the entire repair process on bridge 9462. Two different products, Five Star PileForm F Jacket and grout system and Denso SeaShield FX-70 and grout system, were installed, and contractor feedback was collected during the installation. This type of repair had a very limited impact to the surrounding area compared to a cofferdam-type repair. In fact, the repair was practically invisible to the drivers on the bridge and boaters were able to pass under the bridge while repairs were taking place. The contractor preferred the Denso product due to the jacket being stiffer, which made the jacket want to shut, since visibility in the water was zero. The jacket’s seam was easier to line up. Both products had identical installation steps, and both seemed to be a viable alternative to bridge pile repairs based on the performances from other projects found during the research.

We envisioned a project—a future—where the community is at the forefront of planning and implementation of new technology. Technologies are often developed by select companies and universities, and then tested in communities. Instead of leading with a solution, Community Driven CAV started by understanding community needs and assets, and then creatively explored ways that connected and automated technologies could address them. We wanted the community to drive what technology and use cases we plan for, develop and test. We sought to upturn the usual way of doing business to create a stronger and more equitable transportation future. First the project team conducted three community listening sessions to understand the community’s transportation challenges. Next a workshop with community members and technical experts was held to discuss how CAV technology could potentially help address the identified transportation challenges. This work resulted in potential demonstration concepts for the Creative Enterprise Zone and a Community-Driven Planning Framework, which can be used by others looking to do community led planning.

Asphalt milling is an essential construction activity. It requires concentrated high-intensity applications of force to the existing pavement to remove the asphalt material. The impact that the induced stresses have on the pavement below the mill line is unknown. Consequently, selected milling parameters rarely consider the impact the milling may have on the remaining layers. This study evaluates milling parameters to provide an enhanced understanding of their impacts on the layer directly below the mill line. Five parameters were evaluated and include the time between milling and post-mill overlay construction, existing pavement structure, temperature while milling, depth of milling relative to layer interface, and rotor speed. Pre- and post-milling cores were collected adjacent to each other and evaluated for physical and mechanical properties. The measured properties of the pre- and post-milling cores were statistically compared to determine the impact of milling operations on the integrity of the asphalt concrete immediately below the mill line. Based on the results from this study, it was determined that leaving milled pavement exposed for longer periods of time or milling at cooler temperatures can cause a decrease in the strength of the layer below the mill line and a decrease in the expected pavement life of the new pavement structure. The depth of milling or changing the rotor speed while milling did not have significant impacts on the layer directly below the mill line. In consideration of the results of this study, research with a wider variety of pavements and milling conditions is warranted.

This Research Summary is part of the final deliverable for Research Report 2024-33, "Development and demonstration of a novel Red Light Running Warning System using connected v2i technology.'

Running red traffic signals is a major cause of traffic collisions and resulting injuries and fatalities. Despite extensive prior work on systems to reduce red light violations, they continue to be a major problem in practice, partly because existing systems suffer from the flaw of providing the same guidance to all drivers. As a result, some violations are avoided, but other drivers ignore or respond inappropriately to red light running systems, resulting in safety issues overall. We present a novel method of providing accurate warnings to individual drivers to avoid the broad guidance approach of most existing systems. Recognizing if a driver will run red lights is highly dependent on signal phase and timing, traffic conditions along the road, and individual driver behavior, the proposed warning system contains three parts: a traffic prediction algorithm, an individual warning signal optimizer, and a driver warning display. The traffic prediction algorithm predicts future traffic states along the road towards the signalized intersections using the latest traffic conditions obtained through vehicle-to-vehicle and vehicle-to-infrastructure communications. Then, an optimization problem is formulated to compute the optimal warning signal based on predicted traffic states and driver reaction model. Finally, the optimal warning signal is shown on the display screen to advise driver on how much braking is needed to avoid running the red light. The results of both simulated driving scenarios and real-world road tests show that the proposed system provides more effective and accurate warning signals to drivers, helping them avoid running red lights.

This report is issued to comply with 2022 Minnesota Statutes 174.185.1 Changes to this section were made in the 2024 Legislative Session but do not become effective until July 1, 2025 (see Appendix D). The statute requires a life-cycle cost analysis for every project in the reconditioning, resurfacing and road repair funding categories constructed after July 1, 2011. The LCCA is a comparison of life-cycle costs among competing paving materials using equal design lives and equal comparison periods. Documentation required by the statute includes: • Lowest life-cycle cost • Alternatives considered • Chosen strategy • Documented justification, if the chosen strategy is not the low-cost option

Managing MnDOT’s network of roadways to a satisfactory level of performance requires pavement investment selection methods and activities that consider performing the “right fix” at the “right place” at the “right time” and the “right way.” Although these investment selections consider a broad assortment of investment methods and activities beyond traditional maintenance, maintenance investments and activities play a significant role in roadway pavement performance, often affected by the availability of localized and regionalized resources. To optimize roadway pavement maintenance investment methods and activities, MNDOT Maintenance has determined that the Smooth Roads Project Management Team should be re-established to address this topic.

MnDOT has conducted an annual Omnibus Survey since 1987 (except 2007) in order to gauge public attitudes about various MnDOT services. Participating offices in 2012 included: Maintenance; Traffic Safety and Technology; Transit, including the Bike and Pedestrian programs; Communications; and Customer Relations.

MnDOT has conducted an annual Omnibus Survey since 1987 (except 2007) in order to gauge public attitudes about various MnDOT services. Participating offices in 2012 included: Maintenance; Traffic Safety and Technology; Transit, including the Bike and Pedestrian programs; Communications; and Customer Relations.