Institute for Transportation

About the research

While the demand for using good quality aggregate materials for constructing both highway and local road systems has increased, local availability is often found to be insufficient. The use of recycled waste materials has been used in road construction to the maximum economic and practical extent possible with equal or improved performance. Plastic is a significant contributor to waste generation across the United States. The recent ban on imported plastic waste in developing countries is also forcing US cities and states to take issues related to plastic waste more seriously. Consequently, there is an urgent interest and need to transform plastic waste into useful materials to better to deal with it rather than keeping it in landfills. The objectives of this study are to (1) conduct a synthesis on the use of recycled plastics for roads in combination with the literature review results as part of relevant studies conducted on MnROAD by the National Road Research Alliance (NRRA) and National Center for Asphalt Technology (NCAT), (2) evaluate the feasibility of using plastic waste within roadway paving (asphalt and concrete), (3) recommend which applications will be most beneficial and practical, (4) work in partnership with the Minnesota Department of Transportation (MnDOT) to provide a summary of the work being done locally and within the pool–funded studies with NRRA and NCAT, and (5) work with MnDOT/MnROAD to demonstrate the proof–of–concept for the beneficial applications and identify practical challenges when it is fully implemented in Minnesota’s transportation infrastructure system.

About the research

Pedestrian assets are vital components of urban infrastructure systems, as they provide residents with safe access and active mobility. Like any other transportation asset, these are vulnerable to aging, severe weather, and inadequate construction practices that may lead to rapid deterioration. Generally, pedestrian assets are ill–conceived as low–risk assets and so, many deteriorated assets go untreated or treated inadequately, resulting in unsatisfactory service levels and maintenance backlogs. As such, pedestrian networks require new and more appropriate approaches for condition assessment to guide budget allocation. Under Title II of the Americans with Disabilities Act (ADA), the Minnesota Department of Transportation (MnDOT) is obligated to keep an inventory of pedestrian assets, including sidewalks and curb ramps. MnDOT reports on the compliance of assets each year. Condition rating is one measure of compliance. Condition deterioration of pedestrian assets is not well understood or documented. Understanding how, why, and at what rate pedestrian assets deteriorate will significantly improve MnDOT’s ability to forecast funding needs and will improve project scoping and delivery. Compared to the major transportation assets such as pavements or bridges, pedestrian asset management is still at its early stage. While inventory and condition data have provided a solid foundation, developing performance measures and deterioration models is essential for reliable and informed decision-making. In addition, this project will investigate and document how construction materials, design, and maintenance impact asset deterioration. Deterioration models or assessment frameworks can help determine funding needs and impact asset design and maintenance.

About the research

Fleet managers are continuously challenged with determining the optimal equipment replacement time based on increasing operation costs and decreasing economic value. In addition, they are challenged with determining if a lease or purchase provides the greatest value. Compounding upon these challenges, new equipment purchases and leases can create a negative perception among the general public. This first phase of this research—which consists of a literature review, survey to Minnesota Local Road Research Board (LRRB) members, and follow–up case studies—is strategically designed to understand existing decision support models and methods, quantitative data, and constraints that agencies have when determining the optimal equipment replacement. The second phase of this research—which consists of tool development, validation, and training—is intended to meet the identified challenges and support life–cycle cost analysis (LCCA). This tool will provide quantifiable support for the decision–making process, enabling agencies to make defensible decisions.

About the research

Pedestrian safety at signalized intersections can be improved by reducing vehicle-pedestrian conflicts. The right turn on red (RTOR) maneuver is a source of these conflicts, because RTOR drivers must cross the path of crossing pedestrians, while also searching for gaps in conflicting vehicle flow at the same time. One potential treatment to reduce conflicts is to use a dynamic blank out No Right Turn on Red (NRTOR) sign, which provides an illuminated display of the “No Turn on Red” sign that can be deactivated during conditions when it is not needed, such as when there are no pedestrians present. Because the dynamic NRTOR sign is conspicuous, this treatment may increase driver compliance with NRTOR compared to a static sign, and it may increase efficiency by allowing drivers to execute the RTOR movement at other times. However, at present there is very little guidance regarding the use of blank out NRTOR signs, and only a few studies of their potential effects.The objectives of this research are: (1) to better understand the compliance rates of static and dynamic NRTOR signs; (2) to better understand the maintenance requirements of dynamic NRTOR signs; and (3) to develop recommendations for placement of dynamic NRTOR signs in consideration of their effectiveness in improving safety and efficiency and their maintenance needs.

About the research

This study will perform a long-term assessment of Minnesota air and soil temperatures, precipitation, and freeze-thaw events, to determine the susceptibility of pavement foundation to heavy precipitation events, and to provide a foundation vulnerability assessment of the Minnesota Department of Transportation (MnDOT) road network in response to such heavy precipitation.

A two-phase research approach was developed to achieve these objectives. In the Phase 1 research, a long-term assessment of Minnesota air and soil temperatures, precipitation, and freeze-thaw events was performed. Analysis of Minnesota weather data indicated a 0.5 to 1 in. increase in precipitation before and at the end of the cold season. Based on the findings from Phase I, researchers will study the implications of increased precipitation due to climate change and the performance of road foundations using weather stations and extensive instrumentation data available at MnROAD while also developing a vulnerability map for the state road network.

Focusing on these goals, thin-walled Shelby tube samples will be collected from the MnROAD test facility to determine the hydraulic and thermal properties of pavement materials, in addition to a comprehensive review of existing laboratory data available in the MnROAD database. The thermal and hydraulic properties will be compiled with the in-situ monitoring data to develop mechanistic-based models for predicting the susceptibility of pavement foundation to heavy precipitation events. The developed mechanistic-based prediction models will generate a pavement foundation vulnerability map using a geographic information system (GIS).

About the research

Minnesota Department of Transportation (MnDOT) staff has experienced that pavement markings do not perform well on seal coat and micro surface treated roadways, referred to as “challenging surfaces.” This report serves as a beginning point and organized approach in addressing pavement marking practices on challenging surface roadways.

The project objective was to document existing district practices and issues through several key tasks, which include a literature review, field review, and analysis of existing practice and performance. This effort identified the need for a field trial to provide control in the evaluation of these markings on challenging surfaces. An outline was developed for a future field trial effort, which will evaluate the marking performance of different combinations of pavement marking materials and installation practices.

These project findings will be used in conjunction with the resulting field trial evaluations to improve MnDOT guidance and standard practice that will result in better performance, efficiencies, and roadway safety.

About the research

This project summarizes the development of a scalable, reliable, and practical process for viewing, querying, understanding, and making consistent, objective, and cost effective decisions regarding pavement marking needs, durability, and quality. The research team developed a Web-based pavement marking management system through the development environment of Microsoft Visual Studio 2005 ASP.NET in conjunction with ESRI’s ArcGIS Sever Enterprise 9.2 SP4 functionalities to manage and produce the GIS map resources. The web site hosting itself was done on a Windows based server operating Internet Information Services (IIS). The resulting web based mapping tool provides MnDOT staff the ability to map and query pavement marking retroreflectivity information and serves as a significant resource to both district and central office staff in developing short and long-term pavement marking plans.

About the research

It is becoming increasingly apparent that it is necessary to explore alternative options for cement and concrete production used in public infrastructure to reduce carbon footprint. One possible process is to bubble CO2 in the fresh concrete during production to sequester CO2 and possibly to reduce cement content in the concrete without compromising system performance. Concrete with reduced cement content will exhibit reduced shrinkage reducing the risk of early age cracking. Other CO2 sequestration techniques such as dissolving it in batch water and manufacturing CO2enhanced aggregates also need to be assessed.

Confirming these benefits would be a breakthrough in simultaneously reducing the CO2 footprint while enhancing concrete performance.

Two questions are therefore raised – how much CO2 is sequestered, and what are the effects on the performance of the pavement? The goal of this research is to address these questions through testing, measurements, and the observation of concrete made with CarbonCure technology. The work will also include an assessment of the reduction of the CO2 footprint compared to control mixtures based on determining the amount of CO2 bound in the mixture as well as potential changes in maintenance needs of the pavement over the life of the pavement under traffic and environmental exposure.

About the research

The use of roundabouts in rural areas of the US is growing rapidly. For roundabouts constructed with concrete pavement, joint layout can be especially challenging. To reduce the need for sophisticated joint layouts, consideration is being given to constructing roundabouts without joints and instead using structural fiber-reinforced concrete (FRC) to bridge any cracks that might occur. In 2018, Minnesota’s first jointless FRC pavement roundabout was constructed at the intersection of Minnesota Trunk Highway 4 and County State Aid Highway 29.

The National Road Research Alliance (NRRA) sponsored a study to document the construction and performance of Minnesota’s first jointless FRC roundabout. One of the key objectives was to carry out a three-year performance monitoring regimen of the roundabout to better understand its in-situ performance when exposed to traffic loading and environmental conditions. This report documents the third-year performance of the roundabout as per the requirements of Task 3 of the work plan.

About the research

While pedestrian safety countermeasures contribute to reducing vehicle-pedestrian crashes, their impacts on winter maintenance operations are sometimes overlooked during design. There is a need to investigate the best practice guidance and solutions for the design, installation and maintenance of pedestrian safety features for year-round maintenance. To address this, we conducted a search of literature as well as agency interviews to identify and document current best practices for designing and implementing pedestrian safety countermeasures for year-round maintainability. The countermeasures reviewed included curb ramps, crosswalk markings, corner radii, curb extensions, refuge islands, and speed humps and raised crosswalks. The information collected allowed for the development of conclusions and recommendations for these features. The design dimensions and features of pedestrian curb ramps are established by the Americans with Disabilities Act and should have a slope of greater than 1:12 and a maximum cross slope of 1:50. Durable materials can be used for crosswalk markings, and these can be grooved into the pavement to provide protection from abrasion. Bulb-outs should use a 1:2 or 1:3 upstream taper and a 1:3 downstream taper. When used, tight radii of 15 feet or less should be employed. Refuge islands can range from 6 feet or greater in width, 24 feet to 40 feet in length, with a 4-foot or greater walkway width. Finally speed humps and tables should be between 3-4 inches in height, with lengths of 12-14 feet (humps concave in shape) and up to 22 feet (tables).