In search of enhanced pavement damage detection practices, researchers investigated two innovative additives to asphalt binders: graphite nanoplatelets and taconite concentrates. They also examined the ability of microwave energy to restore subsurface cracking.Continue reading Innovative Materials and Technologies for Sustainable Pavement Infrastructure
This article was originally published in Catalyst, May 2021.
Strategies for managing stormwater runoff have been steadily undergoing a shift in recent decades toward “green” infrastructure. This is a potentially beneficial change, but transportation professionals are beginning to recognize a need for better information on how to properly design, implement, and maintain these facilities.Continue reading A Long-Term Approach to Green Stormwater Infrastructure
Transportation is the number one emitter of greenhouse gas emissions in Minnesota and medium to heavy duty trucks contribute to about 40% of transportation carbon pollution.
While electric cars and buses are becoming more common, medium and heavy duty electric trucks are still in their infancy, and the nationwide infrastructure needs to support them still has to be determined.
In a new study, MnDOT will identify the electric charging infrastructure needed along Minnesota highway corridors to support clean freight transportation.Continue reading New Project: Identifying and Optimizing Electric Vehicle Corridor Charging Infrastructure for Medium- and Heavy-Duty Trucks
This article was originally published in Catalyst, August 2020.
Using “green” infrastructure is a useful strategy for handling city stormwater, which may contain deicers and other contaminants from streets and sidewalks. Choosing the right method and ensuring it doesn’t cause unforeseen damage, however, is another matter.Continue reading Green Stormwater Infrastructure: Tradeoffs and Maintenance
Climate change scenarios have been fairly well-tested and vetted. Moore et al. (2015) found that one of the noteworthy impacts on upper Midwest cities is an increase of storm magnitude of 39% (moderate scenario) to 163% (pessimistic scenario). However, the impact of these scenarios on stormwater infrastructure are not well understood and documented. There are some important financial decisions that need to be made for stormwater infrastructure in the present and near-future, requiring demonstration and discussion of the impacts of climate change on stormwater infrastructure.Continue reading New Project: Climate Change Adaptation of Urban Stormwater Infrastructure
Proprietary technologies, industry competition and federal regulatory concerns are slowing the advent of defined standards for connected and autonomous vehicles (CAVs). Researchers investigated the state of CAV implementation to help local agencies begin preparing for the infrastructure needs of these vehicles. CAV-friendly options are considered for eight infrastructure categories. Since truck platooning is the likely first application of this technology, and optical cameras appear imminent as an early iteration of sensing technology, researchers suggest that wider pavement striping and well-maintained, uniform and visible signage may effectively serve the needs of CAVs in the near future while enhancing infrastructure for today’s drivers.Continue reading Preparing Roads for Connected and Autonomous Vehicles
New solutions are urgently needed to address Minnesota’s aging pavement infrastructure since current materials and technologies can’t keep up with the rate of deterioration and limited funding. MnDOT recently entered into a contract with the University of Minnesota to further explore new materials and technologies – including taconite and Graphite Nanoplatelets (GNP) – that could offer cost-effective solutions for longer-lasting pavement.
The university has investigated the use of taconite aggregates for more than a decade (see ongoing and completed research), and started investigating GNP-reinforced asphalt materials more than three years ago (see recently completed research). Both materials present very unique properties that can be used to better build and maintain asphalt pavements.
This research project will focus on two applications with significant potential in the pavement area:
- Early detection and repair of cracking by developing a novel asphalt material in which GNP materials, taconite concentrate, and conventional asphalt binders are combined for damage sensing and healing. The material damage will be assessed by measuring the electrical resistance, while the damage healing will be achieved by applying microwave to the material.
- Thermal enhancement of tack coat bonding between asphalt overlay lifts, using GNP and taconite concentrate and microwave heating. Poor bonding can result in many different pavement distresses that decrease the pavement structural strength and life, ranging from top-down cracking, potholes and fatigue failure.
Improving pavement durability
The latest data shows that 15 percent of roads in Minnesota are in poor condition, at a cost to each motorist $480 per year. Low-temperature cracking is one of the main causes of pavement failure in Minnesota. Studies have shown that early detection of damage and cracking and timely repair is essential for extending the lifespan of the pavements.
Each dollar spent in the early-stage of pavement life could eliminate or delay $6 to $10 in future rehabilitation or reconstruction costs.
A series of recent studies funded by the National Cooperative Highway Research Program (NCHRP) and MnDOT showed that the GNP-modified asphalt binders and mixtures exhibit a significant improvement in both mechanical and compaction properties. The combination of the previous research and the proposed research will fully explore the properties of GNP-taconite modified asphalt binders and mixtures as a multi-functional pavement material, which will address various needs of MNDOT, including high fracture resistance, efficient compaction process, and cost-effective pavement preservation operations. By addressing these needs, the result of this research will lead to an innovative and efficient means to improve the long-term durability and resilience of asphalt pavements in Minnesota.
The two-year research project aims to explore the damage sensing and healing capability of asphalt binders and mixtures modified by GNP and taconite concentrates. The essential idea is to combine GNP and taconite concentrates with asphalt binders to make the final asphalt products electrical conductive. By measuring the change of electrical resistance, researchers will be able to determine the damage extent. When the damage extent reaches a certain level, the University will apply microwave to the pavement to generate heat, which will heal the cracks through viscous flow of warm asphalt binder. In addition, the thermal bonding capabilities of a novel tack coat material also modified with GNP and taconite concentrate will be investigated. The research will consist of four parts:
- Electrical conductivity tests on GNP-taconite modified asphalt binders and mixtures
- Modeling of relationship between electrical resistance and damage extent
- Investigation of self-healing capability through microwave
- Investigation of a microwave-based tack coat system to enhance thermal bonding in asphalt paving
Join us at the 28th Annual CTS Research Conference to hear about new learning, emerging ideas, and the latest innovations in transportation. This year’s event is scheduled for November 2 at The Commons Hotel in Minneapolis.
Attendees will learn about research findings, implementation efforts, and engagement activities related to a variety of transportation topics. This year’s keynote presentations feature:
- Joung Lee, policy director at AASHTO, on how we pay for transportation infrastructure
- Joshua Schank, chief innovation officer at LA Metro, on policy innovation at his agency
To browse the full program or register for attend, visit the CTS website.
Researchers studied driving behavior at four multilane roundabouts to better understand the relationship between traffic control designs and driver errors. Data collected showed that certain traffic control changes decreased turn violations but failed to eliminate yield violations. Researchers were unable to identify long-term solutions for improving roundabout design and signage, and recommended further research to improve the overall safety and mobility of multilane roundabouts.
“Even though the study did not provide a silver bullet on how to prevent crashes at multilane roundabouts, it did create an efficient tool to analyze and quantify driving behavior data,” said Joe Gustafson, Traffic Engineer, Washington County Public Works.
“This study has advanced our knowledge in multilane roundabout safety and is one step closer to providing much needed improvements to roundabout design guidance,” said John Hourdos, Director, Minnesota Traffic Observatory, University of Minnesota.
What Was the Need?
Roundabouts have been shown to improve overall in-tersection safety compared to traditional traffic signals. However, noninjury crashes are sometimes more frequent on multilane roundabouts than on single-lane roundabouts due in part to driver confusion. Common driver errors such as failing to yield and turning violations on multilane roundabouts have contributed to an increase in noninjury crashes.
Given the benefits of improved mobility, traffic throughput and injury reduction of multilane roundabouts, reducing the noninjury crash rate at multilane roundabouts is important to facilitating their use by Minnesota cities and counties. Identifying solutions to reduce common driving violations would be more sustainable than the current practice of converting multilane roundabouts back to single-lane roundabouts.
In a previous study on a two-lane roundabout in Richfield, Minnesota, researchers demonstrated that traffic control changes could reduce some of these driver errors. However, more data was needed to support study results. Understanding driver behavior and improving traffic control devices are key factors in designing safer multilane roundabouts.
What Was Our Goal?
With limited research on modern multilane roundabouts, the Minnesota Traffic Observatory sought to collect more data to evaluate the correlation between traffic control design features and collisions. Instead of conducting manual observations, researchers used an innovative video analysis tool to collect and process recorded videos of driving behaviors at test sites. Based on the analysis, they attempted to identify driver behaviors and error rates to help reduce noninjury crashes at multilane roundabouts.
What Did We Do?
The research team selected four multilane roundabouts in Minnesota — two in Mankato, one in Lakeville and one in St. Cloud — to observe undesirable driving maneuvers. At each roundabout site, researchers mounted video cameras at key locations to record one to two weeks of driving behavior. Only one roundabout could be observed at a time because only one set of specialized video equipment was available.
The raw videos were processed to produce a data set for analysis. Researchers used TrafficIntelligence, an open-source computer vision program, to automate extraction of vehicle trajectories from the raw footages. They used the same software to correct any errors to improve data reliability. The resulting clean data from the recorded videos were supplemented with historical crash frequency data reports obtained from the Minnesota Department of Public Safety. Collectively, data from both sources allowed researchers to thoroughly investigate the frequency and crash types from the four roundabouts. A statistical analysis of the data revealed that turn violations and yield violations were among the most common driving errors.
Researchers also looked at how violation rates vary with the roundabout’s location and relevant design features. Based on these findings, researchers proposed signage and striping changes to reduce driver errors at the two Mankato test sites. After the changes were implemented, they collected additional video data.
What Did We Learn?
This study provided one of the most comprehensive analyses to date of driving behavior at multilane roundabouts. Researchers were successful in finding solutions for reducing turn violations, but they were unable to identify solutions for yield violations despite the vast amount of data.
Minor differences in the design at each roundabout presented specific challenges. The analysis focused on how each varying design feature impacted driving behavior. Proposed traffic control changes such as extending solid lines between entrance lanes, adjusting the position of yield signs and adding one-way signs successfully decreased turn violations. However, data from before and after traffic control changes showed an insignificant impact on decreasing yield violations. Importantly, the study produced a list of ineffective traffic control methods that can be eliminated from future studies, saving engineers time and money.
The TrafficIntelligence tool was crucial in efficiently processing and cleaning large amounts of raw video. With improvements made to the software program, the tool should be an asset to future research on roundabouts and to other studies requiring observations of driving behavior.
The traffic control changes that were successful at reducing crashes at two-lane roundabouts should be implemented by traffic engineers. In particular, large overhead directional signs or extended solid lines between entrance lanes should be installed to help reduce turning violations. The analysis method used in this study could also be used for a robust before-and-after evaluation of future modifications to traffic control devices.
Additional research could further scrutinize the data already collected, and researchers recommend that more data be collected to examine additional traffic control methods and other intersection design elements to improve the overall safety and mobility of two-lane roundabouts. This research could also serve as an impetus for the study of numerous roundabouts in a pooled fund effort involving several states.
This post pertains to the LRRB-produced Report 2017-30, “Evaluation of Safety and Mobility of Two-Lane Roundabouts,” published July 2017. A webinar recording of the report is also available.
The research project will help the State of Minnesota’s Bridge Office develop a guidance document and a tool for bridge construction time estimation to be used by MnDOT District project managers and construction staff. The tool will provide a range of production rates based on specific design criteria, being more concise based on the level of information available and will aid in evaluating the potential benefit for accelerated bridge construction (ABC) techniques.
“This research will enable District project managers, who may not have bridge knowledge or background, to complete project planning and scoping more effectively,” said Paul Johns of MnDOT’s Office of Construction and Innovative Contracting.
Mike Rief of WSB & Associates will serve as the project’s principal investigator. Johns will serve as technical liaison.
According to the initial work plan, the project is scheduled to be completed by early March 2018, and WSB & Associates will complete the following tasks:
- Conduct an existing practices literature review of current departments of transportation processes around the United States for bridge time and cost estimation.
- Review and compile actual case study bridge construction production rates and cost data for major bridge components from state-provided diaries, schedules and bridge plans.
- Evaluate and select the best software format and style for a bridge construction time estimation tool. Load state case study production rate data into estimation tool and run validation using bridges currently under construction.
- Produce a research report summarizing the literature review on best practices. Produce a user guide for bridge time estimation tool and training presentation.
- An optional task, if the budget allows, will include the development of a cost estimating tool. Cost estimation data would be gathered from the literature review and case study analysis during the development of bridge construction time estimation tool for efficiency.