Building on previous MnDOT-sponsored work, researchers have developed a nondestructive method of assessing pavement thickness using 3D ground-penetrating radar (GPR). A vehicle equipped with an array of transmitting and receiving antenna pairs travels at traffic speed collecting full-width GPR data for analysis, minimizing the amount of pavement coring required.Continue reading Evaluating Pavement Thickness With 3D Ground-Penetrating Radar
Katie Walker, formerly of Hennepin County, was recently named director of MnDOT’s new Office of Research & Innovation (formerly the Research Services & Library section), a role in which Walker will lean on her experience leading organizational change at Hennepin County.Continue reading New Office, Director to Foster ‘Culture of Innovation’
Researchers have found that peat has high potential to replace commercial compost in MnDOT’s standard bioslope and bioswale design for roadside ditches, and that taconite tailings performed comparably to the sand currently specified in MnDOT designs, with the additional benefit of removing phosphates.
Finding alternatives to commercial compost and sand for use in bioswales will help MnDOT meet regulatory requirements for stormwater runoff, while reducing the costs and environmental effects of transporting and storing these materials.
“The results of this project will very much facilitate the development of green infrastructure by reducing its cost to MnDOT and Minnesota local agencies, helping them to do more with less,” said Dwayne Stenlund, Erosion Control Specialist, MnDOT Erosion Control and Stormwater Management.
What Was Our Goal?
The objective of this project was to evaluate peat and muck excavated from construction activities, taconite tailings from area mining operations, and other stormwater quality filter media for use in bioswales and bioslopes along Minnesota highways. Laboratory and field tests of these products would examine their capacity to absorb water, retain pollutants and support plant growth to determine if they are beneficial and practicable in these designs.
What Did We Do?
Researchers began by conducting a comprehensive literature review on the use of bioslopes and bioswales as stormwater treatment best management practices. Then they collected peat and muck near a highway construction project, as well as locally sourced sand, compost, taconite tailings and commercial peat.
These materials, as well as various combinations of materials, were used in laboratory experiments to determine how well they:
- Absorbed water, using a falling head test to measure saturated hydraulic conductivity, which indicates the rate at which water infiltrates a material.
- Retained pollutants, using leaching experiments to quantify how well they removed copper, lead, zinc, nitrate and phosphate.
- Sustained plant growth, using bioassays and greenhouse studies.
Finally, researchers conducted pilot field tests on three plots containing a 50/50 percent peat and sand mixture, and another three plots with a 50/50 percent compost and sand mixture. Between April and August of 2017, they monitored water infiltration, discharge water quality and vegetation establishment for these sites.
What Did We Learn?
“Ultimately, a combination of peat and taconite tailings will compare favorably with current MnDOT specifications for bioslope and bioswale design,” said Kurt Johnson, Research Fellow, University of Minnesota Duluth Natural Resources Research Institute.
Researchers found that peat has a strong potential for replacing commercial compost in MnDOT’s standard bioslope and bioswale designs, and that taconite tailings also performed comparably to the sand currently specified in these designs. However, muck has little potential to replace commercial compost or peat due to its low permeability, poor infiltration and filtration properties, and lack of support for plant growth.
Results for the three properties of interest follow:
- Infiltration rate: While muck had an unacceptably low hydraulic conductivity, peat performed at least as well as compost, and taconite tailings as well as sand. Pilot tests showed that a 50/50 mix of peat and taconite tailings had a similar water storage capacity to a 50/50 mix of compost and sand.
- Pollution retention: Muck absorbed only 50 percent of metals; salvaged peat, commercial peat and compost performed well, absorbing more than 80 percent. However, only taconite tailings showed the potential to remove phosphate. None of the materials removed nitrate.
- Plant growth: Mixtures of compost or peat with sand or taconite tailings all performed well in providing a viable substrate for plant growth. Mixes containing compost performed the best in plant growth trials. Muck was difficult to mix with any other material, and its value for plant growth was minimal. Greenhouse study results showed no difference between sand and taconite tailings in their effect on plant growth response.
In a second phase of this project, “Development and Regionalization of In Situ Bioslopes and Bioswales,” MnDOT will conduct further laboratory tests on alternative materials for bioslopes and bioswales, and expand field tests to several sites in Minnesota that have been constructed using these materials. Researchers also recommend the development of specifications and detail drawings for the use of these materials.
This blog pertains to Report 2017-46, “Comparing Properties of Water Absorbing/Filtering Media for Bioslope/Bioswale Design,” published November 2017.
Lane-departure crashes on curves make up a significant portion of fatal crashes on rural Minnesota roads. To improve safety, solutions are needed to help drivers identify upcoming curves and inform them of a safe speed for navigating the curve.
“Traditionally there are two ways to do this: with either static signage or with dynamic warning signs,” says Brian Davis, a research fellow in the U of M’s Department of Mechanical Engineering. “However, while signing curves can help, static signage is often disregarded by drivers, and it is not required for roads with low average daily traffic. Dynamic speed signs are very costly, which can be difficult to justify, especially for rural roads with low traffic volumes.”
In a recent project led by Davis on behalf of MnDOT and the Minnesota Local Road Research Board, researchers developed a method of achieving dynamic curve warnings while avoiding costly infrastructure-based solutions. To do so, they used in-vehicle technology to display dynamic curve-speed warnings to the driver based on the driver’s real-time behavior and position relative to the curve. The system uses a smartphone app located in the vehicle to provide the driver with visual and auditory warnings when approaching a potentially hazardous curve at an unsafe speed.
“Highway curves [make up] 19 percent of the total mileage of the paved St. Louis County highway system, yet these curves account for 47 percent of all severe road departure crashes,” says Victor Lund, traffic engineer with St. Louis County. “In-vehicle warnings will be a critical strategy to reduce these crashes.”
To begin their study, researchers designed and tested prototype visual and auditory warning designs to ensure they were non-distracting and effective. This portion of the study included decisions about the best way to visually display the warnings and how and when audio messages should be used. “To create the optimal user experience, we looked at everything from how to order the audio information and when the message should play to the best length for the warning message,” says Nichole Morris, director of the U’s HumanFIRST Lab and co-investigator of the study.
Next, a controlled field test was conducted to determine whether the system helped reduce curve speeds, pinpoint the best timing for the warnings in relation to the curves, and gather user feedback about the system’s usefulness and trustworthiness. The study was conducted with 24 drivers using the test track at the Minnesota Highway Safety and Research Center in St. Cloud, Minnesota. The selected course allowed drivers to get up to highway speeds and then travel through curves of different radii, enabling researchers to learn how sensitive drivers are to the position of the warnings.
Based on the study results, the system shows both feasibility and promise. “Our in-vehicle dynamic curve warning system was well-liked and trusted by the participants,” Davis says. “We saw an 8 to 10 percent decrease in curve speed when participants were using the system.”
The project was funded by MnDOT and the Minnesota Local Road Research Board.
Roadside fencing that protects endangered turtles, a toolkit for identifying potentially acid-producing rock and a device that could save MnDOT $200 million a year in pavement damage are just a few of the advancements that MnDOT hopes to make in the near future, thanks to seven recently funded research implementation projects.
Each spring, the governing board for MnDOT’s research program funds initiatives that help put new technology or research advances into practice. This year’s picks aim to improve the environment, reporting of traffic signal data, notification of lane closures and the design and quality of pavements.
Here’s a brief look at the projects (full proposals here):
Protecting the Environment and Wildlife
- To avoid the leaching of potentially acid-generating rock during excavation projects, MnDOT hopes to develop a GIS-based risk-screening tool that identifies areas where PAG rock might be encountered. Guidance will be developed for identifying and handling PAG rock.
Found in bedrock throughout the state – especially northern Minnesota, PAG minerals can release acid upon contact with air or water, a danger to aquatic and human life.
“Anytime we dig, there is the potential to expose this stuff,” said Jason Richter, chief geologist.
- Reducing roadway access for small animals, including endangered turtles, is a priority for MnDOT and the Minnesota Department of Resources. MnDOT will analyze the effectiveness of different types of small animal exclusion fences tried across the state and develop a standard set of designs for future projects.
Improved Reporting of Traffic Signal Data
- A centralized hub of traffic signal data could benefit future vehicle-to-infrastructure (V2I) applications and assist with the modeling of transportation project impacts. Methods and tools will be developed for a regional database of intersection control information that extracts data from MnDOT’s recently acquired Central Traffic Signal Control System and soon-to-be adopted Signal Performance Measure application.
Real-Time Notice of Lane Closures
- In this pilot project, 20 MnDOT arrow board messages will be equipped with technology that automatically reports lane closures on 511 and highway message boards, providing more timely motorist notification.
Longer-Lasting Roads and Improved Quality Control
- This summer, a new quality assurance device called the Rolling Density Meter will be deployed on several pavement projects, eliminating the need for destructive sample cores.
“This is the ultimate in compaction control,” said Glenn Engstrom, Office of Materials and Road Research director. If contractors obtain the right level of density when paving asphalt roads, MnDOT could eliminate $200 million per year in premature road failure.
- In 2018, MnDOT plans to require Intelligent Compaction (a pavement roller technology that reduces workmanship issues) on all significant asphalt projects. A vehicle-mounted mobile imaging device will be piloted that collects necessary supportive roadway alignment data, without the need for survey crews.
- Upgrades to MnDOT’s pavement design software, MnPAVE, (incorporating recycled unbound and conventional base material properties) will help increase the service life of Minnesota roads.
Winter weather events have a regional and often national impact. “Storms never stop at the state line,” said Tom Peters, research and training engineer, MnDOT Maintenance Operations. “That’s why it’s so important for us to know about winter maintenance efforts around the country, and particularly at neighboring states with similar climates.”
MnDOT leads the Clear Roads Transportation Pooled Fund Project (clearroads.org), a national winter maintenance research consortium. In 2015, Clear Roads launched a national survey to collect and report the annual winter maintenance operations of state DOTs. The effort included nearly 50 data points related to equipment, materials and costs.
The results, which are available at clearroads.org/winter-maintenance-survey as a Microsoft Excel-based spreadsheet, are available at no cost for users to examine, analyze and parse as needed. Beyond the raw data, the spreadsheet includes calculated statistics and an interactive map for plotting key metrics.
The results quantified much of what was known only anecdotally and provided useful, actionable data. “Data trends by geographic region and over time let us make more informed operations decisions,” Peters said. “We can also draw on this information to communicate with management, elected officials and the public about how MnDOT’s winter operations fit in a national context.”
As the lead state, MnDOT commits significant administrative time and attention across the agency to Clear Roads. “It’s rewarding and satisfying to see such a useful product as one of the payoffs for all this effort,” Peters said.
Additional data collection for the 2015-2016 winter season is already complete. Look for an update to the online database later this year.
Research in Progress
Clear Roads has nearly a dozen research projects in progress, including:
- An investigation of equipment factors that cause fatigue in plow operators
- A survey of state of practice for contracting for snow and ice control by state DOTs
- A synthesis of best practices for plow route optimization and facility placement
- Development of a decision support tool to quantify the impact of capital improvements on the cost of winter maintenance operations
At its September meeting in Omaha, Nebraska, the Clear Roads Technical Advisory Committee funded five new projects:
- Utilization of GPS/AVL Technology: Case Studies
- Standards and Guidance for Using Sensor Technology to Assess Winter Road Conditions
- Emergency Operations Methodology for Extreme Winter Storm Events
- Weather Event Reconstruction and Analysis Tool
- Training Video for the Implementation of Liquid-Only Plow Routes
What is Clear Roads?
Clear Roads is a 33-member pooled fund program dedicated to winter road maintenance research. Led by MnDOT, Clear Roads projects evaluate winter maintenance materials, equipment and methods; develop specifications and recommendations; study and promote innovative techniques and technologies; and develop field guides and training curricula. Learn more at clearroads.org.
Can Twin Cities roadsides be used to grow habitat for endangered bumble bees? Are unseen factors affecting safety at rural intersections? How should Minnesota transportation agencies be preparing for connected vehicle technology?
Minnesota’s next round of transportation research projects will attempt to solve these and other questions facing the state’s transportation community. The Transportation Research and Investment Group, which governs MnDOT’s research program, and the Minnesota Local Road Research Board, which represents cities and counties, recently met and selected 21 transportation research projects for funding in fiscal year 2018.
A couple of MnDOT’s most interesting projects will evaluate the reuse of wastewater at safety rest areas and truck stations and develop a system to optimize the location of 80 truck stations due for replacement in the next 20 years. MnDOT will also partner with the Local Road Research Board to evaluate the use of personal warning sensors for road construction workers.
In addition to the problem of stripping underneath sealcoats on some city streets, other top research projects for local governments involve pedestrian safety enforcement and investigating whether rural, low-volume roads should be treated differently than urban roads for stormwater runoff. Current regulations govern runoff the same, regardless of daily vehicle count or surrounding land use.
“The selected research studies, which typically take one to three years to complete, will address some of the most major policy, environmental and maintenance dilemmas facing transportation practitioners,” said Linda Taylor, director of MnDOT Research Services & Library.
Below is a list of the selected projects, with links to associated need statements. Final project scopes will become available once contracts are approved. For further information, go here.
Bridges & Structures
- Understanding and Mitigating the Dynamic Behavior of Rural Intersection Conflict Warning Signs and Digital Message Signs Under Wind Loading (PDF)
Materials & Construction
- Remaining Service Life Asset Measure, Phase 1 (PDF)
- Experimental and Computational Investigations of High Density Asphalt Mixtures
- Pavement Thickness Evaluation using 3D Ground Penetrating Radar (PDF)
- Is Seal Coating Counterproductive or Not? (PDF)
- Cost/Benefit Analysis of the Effectiveness of Crack Sealing Techniques (PDF)
- Characterization of Runoff Quality from Paved Low Volume Roads and Optimization of Treatment Methods
- Monitoring and Habitat Assessment of Declining Bumble Bees in Twin Cities Metro Roadsides
- Development and Regionalization of In Situ Bioslopes and Bioswales (summary unavailable)
- Investigating Wastewater Reuse at Truck Stations and Rest Areas (PDF)
- Truck Station Location Optimization (PDF)
- Personal Warning Sensor for Road Construction Workers (PDF)
- Adaptive Management to Improve Deicing Operations (summary unavailable)
Traffic & Safety
- Pavement Markings – Wet Retroreflectivity Standards (PDF)
- Evaluation of the Effectiveness of Stop Lines in Increasing the Safety of Stop-Controlled Intersections (PDF)
- How Locals Need To Prepare for the Future of V2V/V2I Connected Vehicles (PDF)
- Prepare Local Agencies for Future of V2V/V2I and Connected Vehicle Technologies (PDF) (there will be two separate projects evaluating new vehicle technologies- both proposals responded to the same need statement )
- Examining Optimal Sight Distances at Rural Intersections (PDF)
- Evaluation of Sustained Enforcement, Education, and Engineering Measures on Pedestrian Crossings (PDF)
- Cloud-Based Dynamic Warning System (summary unavailable)
The Humphrey School of Public Affairs, in partnership with the Bush Foundation, presented a State Government Innovation Award to recognize great work and to encourage an environment that allows agencies to deliver better government services to Minnesotans through creativity, collaboration and efficiency.
The project, titled Unmanned Aircraft Systems (UAV) Bridge Inspection Demonstration Project, found that using drones for bridge inspections improves safety, lessens traffic disruption and reduces work time. For one type of bridge, inspection time shrank from eight days to five.
In the video, Jennifer Zink, MnDOT state bridge inspection engineer, explains the project, along with Tara Kalar, MnDOT associate legal counsel; Cassandra Isackson, director of MnDOT Aeronautics; and Bruce Holdhusen, MnDOT Research program engineer.
The initial drone project drew significant media coverage and a lot of attention from other state departments of transportation from all over the country.
A second phase of the project was approved year and is currently underway. A third phase is already in the planning stages.
Bees, butterflies and other pollinators busily work on our behalf to help our crops and wild plant life reproduce. Most plants cannot produce fruits and seeds without the aid of these little bugs.
MnDOT is taking steps to ensure that the habitat these creatures depend on gets the protection it needs.
In addition to recently signing an agreement with five other state DOTs to improve pollinator habitat along Interstate 35, a key migratory corridor for Monarch butterflies, MnDOT has just completed a review of other state and local government practices to identify more opportunities to use existing right-of-way to protect pollinators.
“State roadways have acres and acres of habitat ideal for pollinators,” said MnDOT Commissioner Charlie Zelle, during the announcement about the I-35 initiative. “With some careful planning, we can ensure that Monarch butterflies and other creatures that pollinate are able to thrive, which ultimately benefits our food sources and us.”
New Opportunities for Protecting Pollinators
A Transportation Research Synthesis (TRS) released this week underscores MnDOT’s commitment to maintaining roadside habitat for pollinators.
MnDOT set out to learn about the experiences of other state departments of transportation and local agencies in maintaining pollinator landscapes on highway rights of way through partnerships with individuals, groups or local agencies.
Results of the literature review are supplemented with findings from a survey of selected state DOTs and Minnesota counties. Nine state DOTs describe current practices or plans to develop new pollinator-specific partnerships; existing partnerships that have been expanded to address pollinators; and Adopt-a-Highway programs that support maintenance of vegetation in the right of way.
The Transportation Research Synthesis (TRS) may lead to enhancements to MnDOT’s existing practices or the development of a new pollinator-specific partnership program.
While MnDOT does not have a community partnership that focuses solely on promoting pollinator habitat, its Community Roadside Landscape Partnership Program allows Minnesota communities to partner with MnDOT to establish and maintain landscaping in the ROW along highways that traverse their communities, and these landscaping treatments may benefit pollinators.
MnDOT has also partnered with the Minnesota Board of Water and Soil Resources and the Minnesota Department of Natural Resources to establish more than 20 native seed mixes for use on Minnesota roadsides. MnDOT’s online PlantSelector tool includes a seed mix tab to help designers and novices select the right seed for the right place.
Developing the guidance needed to begin using drones for bridge inspections statewide is among the Minnesota Department of Transportation’s latest batch of research implementation projects.
MnDOT recently announced the selection of a dozen research implementation projects for funding in Fiscal Year 2017. In addition to continuing MnDOT’s pioneering drone research, top initiatives aim to improve the accuracy of bridge load ratings and map slopes statewide to identify locations that are vulnerable to flash flooding.
Each winter, MnDOT solicits proposals from staff who want to put local or national research into practice in their day-to-day work.
The state research program’s governing board then selects projects for funding based on benefits, impacts on the department and support from management.
Project champions take previously proven concepts and help MnDOT turn them into useful practices and procedures to make the state’s transportation system better. Funds can be used for equipment, consultant services or researcher assistance.
“The research implementation program fills the gap between research and deployment of new methods, materials and equipment,” Bruce Holdhusen, MnDOT Research Services senior engineer, said.
Here are the 12 newly funded research implementation projects by category:
Bridge and Structures
- Improving Quality of Bridge Inspections Using Unmanned Aircraft Systems (UAS)
- Prestressed Concrete Beam Shear Rating
- OmniScan Phased Array Ultrasonic Corrosion Imaging System
- MnDOT Slope Vulnerability Assessments
- Ultra-thin Bonded Wearing Course (UTBWC) Snow and Ice and Wind Effects
Materials and Construction
- Cold In-Place Recycling (CIR) for Bituminous Over Concrete (BOC)
- Geogrid Specification for Aggregate Base Reinforcement
- Balanced Design of Asphalt Mixtures
- Cone Penetration Testing (CPT) Design Manual for State Geotechnical Engineers
Policy and Planning
- One-year Pilot Test and Evaluation of ASTM DOT Package Compass Portal
Traffic and Safety
- Improve Traffic Volume Estimates from Regional Transportation Management Center (RTMC)
- Understanding Pedestrian Travel Behavior and Safety in Rural Settings