Institute for Transportation

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

• Identify current best practices for designing and implementing pedestrian safety countermeasures for year-round maintainability.
• Document the design characteristics that make pedestrian safety countermeasures easier to maintain during the winter while using existing MnDOT and local agency equipment.
• Review MnDOT and select local agency winter maintenance plans, polices, maintenance agreements, and procedures regarding the safety and accessibility of pedestrians and recommend options for agencies to deal with winter maintenance of pedestrian infrastructure.

About the research

As asphalt pavement oxidizes and ages, bio-materials can be used to restore flexibility to the asphalt pavement. These materials can be used in conjunction with asphalt emulsions to seal and soften weathered pavement. In the current global trade climate, there also exists a need to develop new domestic markets for US agriculture products.

This study investigates further development of using soybean-derived oils to rejuvenate pavement materials. This study is presented with 1:1 matching funds from the United Soybean Board that supports the further formulation and development of a bio-based asphalt rejuvenating fog seal.

The objective of this project is to improve current bio-rejuvenator sealant formulation and achieve stiffness reduction in oxidized, aged asphalt surfaces. The penetration of bio-rejuvenating sealers into the aged-pavement is important for reducing stiffness and restoring flexibility. This research will develop an asphalt emulsion with and without the bio-rejuvenator. The asphalt emulsion will act as the vehicle for the soybean-based rejuvenator. Surface tension reducers for the water-phase will be studied to improve the penetration of the bio-sealant into the asphalt. Particle size of the emulsion is also an important factor for penetration of the bio-sealant. The material developed in this research will be tested at MnRoads on the shoulder of the pavement. Cores will be taken to study the effect of bio-rejuvenating seal on the asphalt. The Minnesota Department of Transportation (DOT) will perform friction testing on the control and test sections to determine the extent surface friction was impacted due to the application of the bio-sealant. The four main steps in this project are (1) bio-sealant emulsion formulation, (2) bio-sealant emulsion application, (3) investigation of stiffness reduction, and (4) studying the effect of the sealant on friction.

About the research

Reduced traffic volumes resulting from COVID-19, along with the strain on enforcement during the pandemic, are thought to have produced higher speeds and more aggressive driving. Understanding the magnitude of speeding and other driver behaviors requires measurement and contrast. This project quantifies reductions in volume and the resulting differences in travel speeds across Minnesota along regular roads and within two work zones prior to and during the novel COVID-19 pandemic. The work includes a review of total crashes as well as fatal and serious injury crashes and includes a survey of law enforcement opinions. Findings based on 125 Automatic Traffic Recorders (ATR) and traffic Sensors quantify volume reductions, which, of course, were lower in 2020 but which varied considerably by location and month. Average speeds overall along with both the number and percentage of vehicles traveling greater than 15 mph over the posted speed limit increased in 2020. This information supports benchmarking and agency decision making.

About the research

The strength and durability of reinforced concrete (RC) bridges are adversely affected by the deterioration of their structural members. When investigating bridges in need of maintenance and repair, the deterioration due to the corrosion of steel rebars is commonly found to be a primary source of structural damage and degradation. To ensure the safety and performance of RC bridges while reducing their direct and indirect costs, an accurate estimate of the extent of reinforcement section loss has central importance for a wide spectrum of engineers and decision-making authorities.

This research project investigated the steps required to achieve such rebar section loss estimates. To achieve this purpose, field assessments of rebar section loss were correlated with available predictive models and later calibrated to condition-specific field data. The outcome, which has been delivered in the form of steel reinforcement section loss guidance tables, directly contributes to understanding variability in rebar section loss when making loss predictions for use in structural evaluation. This facilitates planning preventive and/or corrective actions tailored to the condition state of deteriorating bridge elements.