Category Archives: Maintenance Operations

Maintenance Operations

Adding Snowplow Camera Images to MnDOT’s Traveler Information System

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MnDOT installed network dash cameras and ceiling-mounted cameras on 226 snowplows, approximately one-quarter of MnDOT’s snowplow fleet. The cameras, integrated with the onboard mobile data computer and automated vehicle location equipment, automatically captured snapshots of road conditions during plowing. The snapshots were incorporated into several facets of MnDOT’s 511 traveler information system: the desktop and mobile versions of the website and the 511 app. Motorists and MnDOT alike found the project to be valuable, with the up-to-the-minute imagery helping members of the public and MnDOT’s maintenance staff make well-informed decisions during winter storm events.

“The largest barrier to implementation involved the development of the software package for integrating snowplow cameras into the current AVL system. It required a great deal of back-and-forth to get things right,” said oe Huneke, Maintenance Decision Support Systems (MDSS)/AVL Section Manager, MnDOT Office of Maintenance.

“We did research to make sure the cameras did not block drivers’ views, taking state and federal regulations into consideration, and we tested the cameras to make sure they were capturing images at the right resolution,” said Jon Bjorkquist, Maintenance Technology Development/ Implementation Coordinator, MnDOT Office of Maintenance.

What Was the Need?

Reliable information about road conditions during winter weather allows motorists to make informed travel decisions and helps MnDOT responders maintain roads. While meteorological updates on a winter storm and automated status reports on Minnesota’s snowplow fleet are important sources of data, they do not provide visual information about road conditions.

In 2015, a pilot project allowed MnDOT to take road condition pictures from cameras mounted on selected snowplows during winter storms. The system was limited, however. Few snowplows were outfitted with these cam-eras, images were not available to the public, and network infrastructure did not allow for easy scaling. A larger scale program was needed to capture road imagery taken from snowplows across Minnesota and to share the pictures with Minnesota motorists.

What Was Our Goal?

MnDOT sought to install cameras on a sizable portion of MnDOT’s snowplow fleet. In addition to making hardware and network enhancements to collect and compile the image data, MnDOT also set out to make the photos avail-able in near-real-time to its internal maintenance staff and the traveling public.

Camera mounted on the ceiling of a MnDOT snowplow cab.
To capture images of road conditions, MnDOT mounted cameras in the cabs of one-quarter of MnDOT’s snowplow fleet.

What Did We Do?

In 2015 and 2016, MnDOT installed network dash cameras and ceiling-mounted cameras on 226 snowplows, approximately one-quarter of the agency’s total snowplow fleet. The cameras, integrated with the onboard mobile data computer and automated vehicle location (AVL) equipment, automatically captured snapshots of road conditions during plowing. This system included the following key operational features:

  • The dash cameras automatically recorded images whenever the computer-AVL system was on.
  • The cameras recorded an image of the road ahead of the plow.
  • Images were taken once every five minutes and were only retained if the plow was moving at least 10 mph.
  • The cameras were capable of taking operator-initiated snapshots and video clips.
  • Video clips could be classified into three categories: accident, general interest or work zone.

The system sent the plow camera images and metadata (geolocation, plow, camera and conditions) to a MnDOT server upgraded to accommodate the data. MnDOT set a data retention schedule for mobile snapshots and video segments as well as the data server.

Plow images were incorporated into several facets of MnDOT’s 511 traveler information system, including the desktop and mobile versions of the website and the 511 app. Plow images plotted at 10-minute intervals on the 511 maps provided motorists with up-to-the-minute, easily accessible information on road conditions. The images were also incorporated into MnDOT’s internal website called Condition Acquisition and Reporting System.

What Did We Learn?

The project demonstrated the successful integration of various hardware, software and network systems, carrying the road weather imagery step by step from the cameras to the public 511 interface. The project also succeeded in scaling up an earlier, modest effort to furnish snowplows with cameras.

In addition, MnDOT collected input on the value of the cameras from a range of interested parties: the public, snowplow operators and supervisors, and MnDOT management staff.

The public response was overwhelmingly positive, with 319 Facebook users responding to a MnDOT post about the cameras. All the respondents used positive emote icons (“heart” or “thumbs up”). Several members of the public provided responses through Facebook and MnDOT’s “Contact Us” Web page about the value of being able to view actual road conditions, though others expressed concern about the cost of the system.

Surveys of MnDOT snowplow drivers and supervisors and interviews of MnDOT managers revealed that supervisors and managers had a largely positive view of the program as well. Drivers provided mixed reviews. Comments from these groups yielded the following recommendations about implementing a program of this nature:

  • Perform outreach efforts that clearly communicate benefits to achieve broad buy-in from snowplow drivers. Provide training and follow-up instruction on use of the cam-era’s features to encourage drivers to use the manual snapshot and video features.
  • Address drivers’ concerns about privacy (such as “Big Brother is watching”) directly, and understand that these concerns have lessened over time. Supervisors should be advised not to react too quickly to privacy concerns.
  • Address concerns about in-cab distraction by adjusting the system configuration or hardware. This might include making dash camera screens dimmable at the driver’s option, or placing screens and cameras out of critical sightlines.

What’s Next?

This project was a success, with snowplow camera images providing significant benefits to MnDOT staff and the traveling public. Based on this work, MnDOT plans to install camera systems on additional snowplows in the state fleet—as deemed necessary by district management—and to continue displaying snowplow images on MnDOT’s 511 system.

This post pertains to Report 2017-41, “Installing Snowplow Cameras and Integrating Images into MnDOT’s Traveler Information System,” published October 2017.

Maintenance Operations

Pothole Patching Study Yields Best Practices Guidance

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Researchers identified four pothole repair methods suitable for Minnesota: cold mix, hot recycled asphalt, mastic material and mill-and-fill with hot-mix asphalt. They tracked the performance of each method at five sites in northern Minnesota for two years. Using the results from this monitoring period, researchers developed decision trees for selecting an appropriate repair method and best practices for using each method. The decision trees were developed in two formats: as a flowchart that can be used in a maintenance guide and as flash cards that can be laminated and used by maintenance crews for quick reference in the field.

“We wanted to develop a decision tree for choosing the right pothole repair method that could be laminated for use in the field,” said Susan Lodahl, Assistant State Maintenance Engineer, MnDOT Office of Maintenance.

“This project offers help deciding what kind of pothole patch is appropriate for the conditions, including the pothole dimensions, location in the roadway and the season,” said Manik Barman, Assistant Professor, University of Minnesota Duluth Department of Civil Engineering.

What Was the Need?

Repairing potholes is one of the most public of road crews’ duties. Drivers notice cracks and holes, and feel the effects of short-term repairs that kick up gravel as wheels roll over patched holes.

Selecting the appropriate patching method and materials varies depending on several factors, including the size of the pothole and its location on the roadway. Patching methods and materials face seasonal challenges too. In northern Minnesota, asphalt plants shut down for the winter and don’t reopen before March, if then. Potholes that are repaired in cold weather aim for short-term fixes with patches that can be replaced when warm weather returns or when the pavement can be milled and overlaid with hot-mix asphalt (HMA). Road crews have tried applying HMA in winter using various heating systems and in-place recycling methods, but even warm weather patches only offer semipermanent repair.

Whether it’s spring, summer, fall or winter, choosing the best, most cost-effective or durable pothole repair method has remained a complicated puzzle, one that MnDOT would like to help road crews solve.

What Was Our Goal?

MnDOT funded this research to help road crews choose patching methods that match specific repair conditions. Researchers explored patching tools, materials and methods to identify those most appropriate to specific pothole conditions, road locations and time of year. They also evaluated the effectiveness of different methods based on durability, road safety, ride quality, driver satisfaction and other factors.

A researcher conducts a test on a pothole
A researcher conducts an on-site permeability test to determine how well a pothole repair seals and resists water penetration.

What Did We Do?

Research began with a comprehensive literature search of pothole repair methods in Minnesota and other states. From this search, investigators identified four repair methods that best suit Minnesota: cold mix, hot recycled asphalt, mastic material and mill-and-fill with HMA.

With help from the study’s Technical Advisory Panel, researchers identified five sites in MnDOT District 1 near Duluth, Minnesota, where they oversaw 20 pothole repairs. Investigators monitored these repairs for about two years before assessing the methods and their best applications. Researchers then developed decision trees to help road crews choose the most suitable method for each repair and compiled best practices to provide further guidance.

What Did We Learn?

The best practices describe the best uses of each of the four pothole repair methods along with guidelines for preparing the pothole for repair and placing the patching materials.

Cold-mix patches should be placed only in shallow potholes with depths of 2 inches or less. Deeper potholes should be repaired in two lifts, each compacted with a handheld compactor to prevent dishing or denting when the cold mix settles.

Hot mixes using recycled materials should be avoided. The aged binder slows the heating process, and its fines inhibit the bonding of the new binder and aggregate. The new binder also doesn’t seem to rejuvenate the old, and the patches age more rapidly. When hot mix is used for pothole repair, a handheld compactor is required. Recycling mixers such as the Stepp SRM 10-120 should be used to create virgin hot patch material using asphalt oil and sand or small aggregate.

Mastic material provides a smooth driving surface but appears to dish in potholes along longitudinal cracks because the material lacks the strength to support loads. Mastic should only be used on centerline joints and longitudinal joints along shoulders, where it stays in place. It should not be used in wheel paths.

Mill-and-fill with virgin HMA, when constructed with care, can be effective in eliminating dishing and raveling at the patch-pavement interface. Sufficient tack material must be used, and trucks should not be allowed to drive on the tack. The pothole should be filled with the proper amount of HMA, and the patch must be compacted sufficiently. Failure to carefully apply mill-and-fill can lead to significant deterioration at the patch-pavement interface after about 100 days, which can contribute to additional damage in the distressed area.

Using the findings from this study, researchers developed guidelines for patching method selection, placement, compaction practices and moisture control. They also developed decision trees for selecting the appropriate repair method for conditions. The decision trees are available in two formats: as a flowchart for use in maintenance guides and as flash cards for quick reference by maintenance crews in the field. The final report includes best practices and a step-by-step pictorial guide to patching.

Simple Decision Tree for Comprehensive Field Evaluation of Asphalt Patching Techniques

What’s Next?

The decision trees and best practices developed in this study can be easily combined into a patching guide that, with laminated flash cards, can be distributed to MnDOT road crews around the state. This research could be amplified by repeating the process with more pothole repairs in other areas of Minnesota to increase data for performance evaluation and analysis of best practices.

This post pertains to Report 2017-25, “Comprehensive Field Evaluation of Asphalt Patching Methods and Development of Simple Decision Trees and a Best Practices Manual,” published June 2017. 

Environment, Maintenance Operations, Research

New recommendations aim to help roadside turfgrass thrive

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Keeping Minnesota’s roadsides green is about more than just aesthetics—healthy turfgrass can improve water quality, reduce erosion and road noise, and provide animal habitat. However, harsh conditions such as heat, drought, and salt use can make it difficult for roadside turfgrass to thrive.

In 2014, as part of a study funded by the Minnesota Local Road Research Board (LRRB), researchers in the University of Minnesota’s Department of Horticultural Science identified a new salt-tolerant turfgrass mixture that could be used on Minnesota roadsides. But, when MnDOT began using the mixture, called MNST-12, the agency experienced a series of installation failures.

Now, led by Professor Eric Watkins, the research team has identified new best management practices for installing and establishing this type of salt-tolerant turfgrass.  The study, funded by the LRRB, specifically focused on watering practices, soil amendments, and planting date for both seed and sod.

“Newer improved seed or sod mixes like MNST-12 may have differing requirements for successful establishment compared to other species or cultivars that contractors and other turf professionals are more familiar with,” Watkins says. “Since all of these management practices are prescribed—or not prescribed—in the MnDOT specifications, generating data that can inform future specifications is a valuable outcome of this work.”

The study, which was conducted over several years, included experiments on how water should be applied to new MNST-12 turfgrass installations, the use of soil amendments at the time of establishment, and the effect of the seeding or sodding date on the success of a new planting.

Researchers tested turfgrass watering requirements using an automated rain-out shelter. Photo: Matt Cavanaugh

Based on their findings, the researchers recommend these changes to MnDOT specifications:

  • No soil amendments are necessary, but adequate seedbed preparation is important.
  • Seeding is preferred to sodding between August 15 and September 15.
  • Sodding can be permitted throughout the year, but only if the installer is able to supply frequent irrigation.
  • When watering in sod, attention should be given to the species being used and local rates of evapotranspiration (evaporation from both the soil and plant leaves). Sod installers can anticipate using between 100,000 and 170,000 gallons of water per acre to ensure a successful establishment.
  • Sod can be mowed as soon as sufficient root growth prevents an operator from manually pulling up pieces by hand, but it should not be mowed if wilting from heat or drought.

Currently, the researchers are using the results of this project to develop methods for educating and training stakeholders, including turfgrass installers, on these best management practices. They are also developing systems that could be used by installers in the field to help maximize the success rate of turfgrass installations.

“These best management practices can help limit installation failures and reduce maintenance inputs for future installations, providing both an economic and environmental benefit,” Watkins says.

“The knowledge and improved specifications we gained through this research will allow us to make our contractors more successful, which makes MnDOT successful,” says Dwayne Stenlund, MnDOT erosion control specialist. Because local agencies often rely on these MnDOT specifications as a guide for their projects, they will also benefit from the improved practices.

Stenlund also says the new specifications—especially those related to watering requirements—could allow for a clearer understanding of the true cost and value of turfgrass installation and maintenance work, which could ultimately improve the accuracy of the project bidding process.

In another project, the research team is exploring other turfgrass stresses, such as ice cover and heat. They are also testing additional turfgrass species and mixtures in an effort to continue improving MnDOT specifications for roadside turfgrass installations.

Maintenance Operations

AVL Technology Enables Smarter, More Efficient Mowing Operations

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A pilot project was begun to study the use of AVL technology in mowing operations. Potential benefits include improved mowing efficiency, improved reporting and ease of supervision, reduced paperwork and reduced spread of noxious weeds.

“Using the data we get from the AVL project, we can estimate how long it will take to mow the entire system,” said Douglas Maki, Asset Management Engineer, MnDOT Metro District. “That way, we can plan far in advance of major holidays, when the most traffic comes through our system.”

“The AVL technology can be used to mark newly disruptive weed locations and anything else a mower operator might see, like potholes, damaged signs or guardrails, and excessive or dangerous debris in the field,” said Adrian Potter, Senior Associate, SRF Consulting Group, Inc.

Potter served as the project’s principal investigator.

What Was the Need?

MnDOT is responsible for mowing roadsides along 14,000 centerline miles of highways for environmental and safety reasons. This is an enormous and critical task, requiring efficient use of employee time and mowing equipment, and efforts to avoid the spreading of noxious weeds, which will lead to increased use of herbicides.

A promising technology that many departments of transportation (DOTs) have installed is automated vehicle location (AVL). AVL systems provide a precise geographic location for DOT-owned vehicles so that real-time data can be obtained on field operations. This technology has been used for snowplowing and other fleet vehicle operations. However, only a few DOTs have used it for mowing operations.

To determine if AVL technology should be used in its
mowing operations, MnDOT undertook a pilot project involving 30 of its mowers. The locations chosen were Metro District roadsides, as MnDOT had previously invested in creating a geographic information system map of noxious weeds on those roadsides.

What Was Our Goal?

The goals of the pilot project were to:

  • Generate protocols for hardware installation and software training.
  • Set up the system for communicating data from the mowers to internal MnDOT servers.
  • Develop accomplishment reports based on data collected by the AVL units.
  • Develop and provide initial training to operators and supervisors.
  • Optimize the mower routes used.

What Did We Do?

For the 2015 and 2016 mowing seasons, researchers fitted 30 Metro District tractors with AVL technology, sensors and communication equipment.

The first stage of the project focused on developing the software interface required for the AVL system. The application had to provide a view of the mower’s exact location so that the mower operator could avoid noxious weeds. Data would be collected through an in-vehicle controller unit and transferred to MnDOT for analysis via a Verizon AirCard system installed on each mower.

Mechanics installed metal racks within each of the 30 mowers to protect the Ameritrak AT-500 AVL hardware unit. A video screen was mounted on the top of the rack. A reporting system was developed for use by operators, supervisors and managers. Training sessions were scheduled at the start of each season and when new operators were hired.

Interior view of mower cab showing location of AVL unit.

What Did We Learn?

The project achieved its initial goals of developing protocols for hardware and software, creating electronic reporting and capturing real-time data.

The research team gained the following insights during the planning and field-testing stages of the project:

  • Substantial time is needed to adequately develop and test the AVL software and hardware.
  • Implementing the system also requires considerable time due to resource limitations, and after implementation, it takes multiple mowing seasons to quantify weed and herbicide reductions.
  • MnDOT mower operators and supervisors recognized the value of the AVL system in improving the efficient use of their time, eliminating the drafting of written reports, and giving MnDOT a more accurate record of acreage mowed.
  • Since the tractors operated at such slow speeds, the initial data captured were too imprecise to analyze. But with software adjustments, this issue was resolved.
  • Installation of the AVL unit could have an impact on the operation of the tractor because the additional electrical burden that the unit places on the tractor battery may require the tractor to be sent to the manufacturer for inspection.

What’s Next?

The initial success of the pilot project provided the basis for continued use of AVL technology in Metro District mowing operations during the 2017 season and possibly beyond. MnDOT is currently evaluating whether this project has provided enough data to expand AVL to other districts in the state. The investigators estimate that after full implementation, MnDOT could save $100,000 per year.

MnDOT may consider installing AVL technology in other agency equipment to optimize and monitor maintenance activities.

This Technical Summary pertains to Report 2017-11, “An Innovative Approach to Smarter Mowing, Utilizing Automated Vehicle Location to Enhance Mowing Operations,” published April 2017.

Additional materials:

Maintenance Operations, Research, Traffic and Safety

Reducing speeds to improve safety for work-zone flaggers

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When drivers approach a roadway work zone at high speeds, they put the lives of work-zone flaggers at risk. To keep flaggers safe on the job, U of M researchers are looking for better ways to capture drivers’ attention—and compel them to slow down—as they approach flagger-controlled work zones.

Kathleen Harder, director of the Center for Design in Health, and John Hourdos, director of the Minnesota Traffic Observatory, identified and tested new work-zone warning elements to more effectively capture and sustain driver attention. The project was funded by MnDOT and the Minnesota Local Road Research Board.

The project began with a simulator study in which participants completed three drives, each featuring a work zone with different warning treatments. One condition was a traditional four-sign configuration currently used to warn drivers approaching work zones. The other two conditions featured a variety of new elements, including signage with new messaging such as  a “one-lane road ahead” sign with flashing LED lights, a dynamic speed warning sign equipped with a loud warning horn that sounded if drivers exceeded the speed limit, and portable rumble strips.

“Overall, we found that the new set of elements is more effective than the elements currently used to reduce driving speeds on the approach to a flagger-controlled work zone,” Harder says.

Although adding LED lights to the one-lane road sign had no significant effect on drivers’ speeds, findings indicated that the dynamic speed sign coupled with the horn was more effective than the dynamic sign alone.

To test these new elements under real-world conditions, the researchers conducted field tests evaluating two configurations in Minnesota work zones. The first configuration followed the minimum standards outlined in the Minnesota Manual on Uniform Traffic Control Devices. The second deployed signs employing new messaging and attention-getting devices, including a dynamic speed warning sign, horn, and rumble strips.

Findings showed that the combination of the dynamic speed warning sign and the horn successfully reduced the overall speed of vehicles approaching the work zone. The portable rumble strips did not cause any significant speed reduction, but this may have been related to their location downstream from the dynamic speed sign and horn.

“Our findings reveal that the new set of elements designed to capture driver attention—including new messaging, a dynamic speed trailer, and horn—had a significant influence on reducing driver speed,” Harder says. “The experimental layout practically eliminated high-speed outliers and successfully reduced the approach speed to the flag operator.”

Maintenance Operations, Research

Winter Decision-Making Crosses State Lines

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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:

See all of Clear Roads’ current research projects at clearroads.org/research-in-progress.

What’s Next?

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.

Environment, Maintenance Operations, Research

10 Ways Transportation Research Keeps Minnesotans Moving in the Winter

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As the first big snow and ice storms sweep through parts of Minnesota today, we’d like to remind you of some of our great winter weather research studies. Here’s a list of some of this winter-related research from MnDOT and the Local Road Research Board:

Living snow fences

Living snow fences are trees, shrubs, native grasses, wildflowers, or rows of corn crops located along roads or around communities and farmsteads. These living barriers trap snow as it blows across fields, piling it up before it reaches a road, waterway, farmstead or community. Through multiple research efforts, MnDOT continues to advance its practices for living snow fences. Willow plants, which are which are inexpensive and fast-growing, are a new form of snow fence. MnDOT has also developed a tool that allows the agency to better offer a competitive payment to farmers.

Related studies:

Permeable pavement

According to recent studies, researchers believe Minnesota could eliminate salt usage on low-volume local roads by switching to permeable pavements. Permeable pavements — pavements that allow water to seep through them — have been studied in some Minnesota cities, and a research project is currently underway to further investigate how much salt reduction can be expected.

Related studies:

Traffic recovery during winter storms

MnDOT’s Metro District developed a way to automatically determine when to stop plowing a highway after a snow storm. The method involves measuring traffic flow to determine when road conditions have recovered. Current practice calls for maintenance workers to visually inspect traffic lanes. The automated technique could potentially be more accurate and save time and costs.

Related study:

Salt and other deicing chemicals

Minnesota winters are no joke, and Minnesotans still need to get wherever they’re going despite harsh snow and ice conditions. That’s why MnDOT is constantly researching new and improved versions of salt and other deicing chemicals to keep roads safe at the least amount of damage to lakes, rivers and groundwater.

Related studies:

Snowplow blades

A couple years ago, MnDOT snowplow operators in southwestern Minnesota invented an experimental plow that uses the wind to cast snow from the road without impeding traffic or the operator’s view. This winter, MnDOT intends to test multiple types of snowplow blades as part of a larger research project comparing types of deicers.

Related study:

Snowplow technology

While a lot of research has been done on the plow itself, MnDOT hasn’t forgotten to invest in research to improve in-cabin snowplow technology as well. Some of the great technology recently developed to assist snowplow drivers, includes a driver assist application that a MnDOT plow driver used last winter to navigate a storm and rescue stranded motorists. The agency is also studying equipment factors that can cause fatigue in snowplow operators.

Related studies:

Salt-resistant grasses

When the snow melts every spring, the damage salt does to roadside grass is obvious. That’s why researchers have spent years looking into developing and implementing salt-tolerant grasses on roadside settings. The result of this effort has been the introduction and use of salt-tolerant sod and seed mixtures that are made up primarily of fine fescue species. MnDOT is also studying how chlorides are transported within watersheds in order to better focus efforts to reduce deicer usage in  areas where it will have the biggest environmental impact.

Related studies:

Cold-weather cracking prediction test

MnDOT has developed a test that can tell whether a contractor’s proposed asphalt mix will cause the road to crack in the winter. Building roads using better asphalt mixes leads to less cracking and fewer potholes. The test is expected to save the state about $2 million per year.

Related studies:

Pedestrian snow removal

It’s not all about cars and trucks. Minnesotans still ride bikes and walk in the winter. That why MnDOT assembled a comprehensive review of existing practices and policies from other states, as well as a summary of valuable publications that could be referenced while developing a new policy.

Related study:

Maintenance Decision Making

MnDOT research led to the development of a Maintenance Decision Support System and related components provide real-time, route-specific information to snow plow drivers, as well as recommended salt application levels. These recommendations have reduced chemical usage while still achieving performance targets for snow and ice clearance.

Related studies:

Environment, Maintenance Operations, Research

Knowing While Mowing: GPS Keeps Maintenance Workers Out Of the Weeds

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As temperatures fall and days get shorter, MnDOT Metro District maintenance workers are wrapping up a season of mowing grass along roadsides and in medians that they hope will prove a little more efficient than in the past.

Thanks to a research project that installed GPS devices in tractor cabs, operators have a better sense of exactly which areas they need to mow and which areas should be left alone. Five Metro District tractors were tested in 2015. This year, more than 40 tractors were fitted with the automated vehicle location (AVL) technology, which includes a GPS antenna, an on-board central processing unit (CPU) and an in-cab screen with a user interface.

Trisha Stefanski, Metro District asset management engineer, expects one of the biggest benefits of the project to be a reduction in herbicide use. Maintenance crews use herbicide to control the spread of noxious weeds that sometimes get spread during mowing operations. Mapping exactly where noxious weeds are, and providing that information to operators on a real-time, in-cab screen and user interface helps them mow around those areas.

“We’re really hoping it will reduce the amount of herbicide that we’re putting on our roadways by 50 percent,” Stefanski said. “We’re not certain that will be the number, but that’s what we’re hoping for. We think just not mowing those areas will not spread as many noxious weeds and so we don’t have to apply as much herbicide.”

Metro District operators, such as Jesse Lopez, give the AVL technology rave reviews.

“Basically you can see what you shouldn’t mow and what you should mow. So, it makes it easy for me. It’s just like playing a game,” Lopez said. “This actually helps me to optimize what my job is. I know exactly where I’m at and where I’m going. I think everyone should use it – absolutely everybody who is in a mowing situation or a plowing situation.”

In addition, the AVL technology helps maintenance supervisors keep tabs on exactly where their operators are in real time. It also helps supervisors complete reports by automatically providing the geographic areas where mowing has been completed.

Stefanski says the project has gone really well, and she hopes collecting more data over another mowing season will show real savings on herbicide use. In the meantime, she is thinking of other ways AVL technology could be applied to maintenance operations.

“What I really like about the project is that we are taking something used in a lot snow plows and a lot of other technologies – cars, other things, maybe UPS uses them – and we’re putting it into maintenance operations,” Stefanski said. “Having it for mowing, we can also use it for smooth pavements. We can also use it for other things in mowing operations.”

Maintenance Operations

Driver-assist system helps keep plows on the road

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Darryl Oeltjenbruns, snowplow driver in District 7, operates the only driver assist system, or DAS, equipped snowplow in the state. The system helps snowplow operators see road alignments and features such as turn lanes, guardrails and road markings. (Photo by Chase Fester)
Darryl Oeltjenbruns, snowplow driver in District 7, operates the only driver assist system, or DAS, equipped snowplow in the state. The system helps snowplow operators see road alignments and features such as turn lanes, guardrails and road markings. (Photo by Chase Fester)

By Sue Roe, MnDOT Communications

Southwest Minnesota has the highest average wind speeds in the state—bad news for MnDOT snowplow operators who often drive in low visibility to clear roads.

“We have more days when the wind blows than when it doesn’t,” said Chase Fester, MnDOT District 7 transportation operations supervisor. “We struggle with the wind.”

That’s why District 7 is piloting a snowplow driver-assist system (DAS) developed by University of Minnesota researchers to combat the blowing snow and fog that often cause zero visibility. The DAS helps snowplow operators see the road alignment and features, such as turn lanes, guardrails, and road markings. Even in less extreme winter weather, snowplow operators gain assurance of their lane location using the system.

The driver assist system displays a white box on the screen when an obstacle, or in this case a mailbox, is located. If the object appears in the lane, such as a car stuck in a snow drift, the box turns red and gets bigger as the snowplow gets closer to the object. (Photo courtesy of MnDOT District 7)
The driver assist system displays a white box on the screen when an obstacle, or in this case a mailbox, is located. If the object appears in the lane, such as a car stuck in a snow drift, the box turns red and gets bigger as the snowplow gets closer to the object. (Photo courtesy of MnDOT District 7)

The DAS was developed and refined over the past 20 years under multiple research projects funded by MnDOT and the USDOT’s University Transportation Center program. Professor Max Donath, director of the University of Minnesota’s Roadway Safety Institute, led the work. In addition to plows, the DAS technology has also been applied in other specialty vehicles such as patrol cars and ambulances. Numerous vehicles using the system have been deployed in both Minnesota and Alaska.

The DAS uses GPS technology and a front-mounted radar to provide an image of the road and any obstacles in front of the operator. The image is displayed on a monitor inside the cab of the plow. The system also vibrates the operator’s seat as a warning if the plow veers too close to the roadway’s centerline or fog line.

“If the driver gets within one foot of the fog line on the right side, the right side of the seat vibrates. If the driver gets too close to the centerline on the left side, the left side vibrates,” said Fester.

The vibrations continue until the driver moves back into the center of the lane. The driver can also turn off the warning feature to clear snow from the shoulder.

The DAS is currently installed in one truck in District 7. The $75,000 cost makes it difficult to install in every truck in the district or the state, although having at least one system in every district may be possible, Fester said.

Fester said the system proved its worth one day in February when blizzard conditions caused zero visibility and forced many road closures in southwest Minnesota. He was called out at 2 a.m. Feb. 8 to assist a stranded state trooper and several motorists on a 12-mile stretch of Hwy 60 between Windom and Heron Lake. Fester drove a pickup behind the DAS-equipped snowplow, driven by Darryl Oeltjenbruns, to reach them.

As the DAS identified stranded vehicles on the way to Heron Lake, Fester and Oeltjenbruns checked to make sure they weren’t occupied with people. Once they made it to Heron Lake, they stopped at the community center, where the state trooper and the stranded motorists he brought in were located.

On the way back to Windom, Fester and the state patrolman continued to check on stranded vehicles as the DAS-equipped snowplow led the way. If the vehicles weren’t in the ditch, motorists drove behind the two MnDOT vehicles. If their vehicles were in the ditch, motorists rode in a Suburban that was also being escorted to Windom. After returning to Windom, the motorists were dropped off at motels or truck stops.

“When we first went out, there were about six stranded vehicles. Coming back from Heron Lake, there were about 15,” Fester said. “At one time, we had 12 vehicles in line as we drove back to Windom, driving about 10 to 15 miles per hour.”

Later that morning the DAS system was used again to locate other motorists.

“We continued to use it until about 10 a.m. or 11 a.m. that day,” Fester said. “The system worked great and kept everyone safe. It was an interesting morning.”

(Reprinted and adapted with permission from an article by Sue Roe in MnDOT’s Feb. 17, 2016 Newsline.)

Maintenance Operations, Research

Willow shrubs could be next great Minnesota snow fence

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The benefits of living snow fences and other snow control tools to keep roadways clear of blowing and drifting snow have been known for decades, and MnDOT has been using a variety of these techniques for years to catch  snow before it gets to a road.

Living snow fences often consist of trees, grasses and even corn stalks left standing in a farmer’s field.  Now willow shrubs are being added to the list as a fast-growing, inexpensive snow control measure.

What’s new

WillowSeptember
Fish Creek willow shrubs (left) grow alongside corn in September 2015.

Researchers recently completed a study that investigated whether willow shrubs could make good living snow fences. While typical snow-fence plants, such as dogwood or cranberry shrubs, can take five to 20 years to establish themselves, shrub willows were effective at trapping snow after just two growing seasons, according to the study.

In spring 2013, researchers installed three varieties of shrub willow side-by-side in two-row and four-row configurations along about a quarter of a mile of Highway 14 in Waseca, where snow drifts are an issue. In April 2014, they cut the shrubs down to the ground  to encourage branching and bush density. Though the trimmed willows had little impact on drifting snow the first winter, each willow-shrub plot was collecting two to three metric tons of snow by the second winter, according to the research report. Researchers believe that after three or four growing seasons the willow shrubs could catch the entire mean annual snowfall on the site.

In the four-row configuration recommended by researchers, costs of raising, furnishing, planting and mulching came to about $3.60 per plant, which is dramatically less than the contract bid cost for traditional living snow fence species that cost more than $50 per plant. In addition, the willow shrubs could be harvested and sold as biomass every few years to provide an income source.

Past research

Willow trees is just the latest advancement in the state’s snow control program. A 2012 research project evaluated the costs and benefits of living snow fences and provided MnDOT with a payment calculator to determine how much to compensate landowners for installation and maintenance costs.

A recent research implementation project created a mobile-friendly Web version of the payment calculator tool.  The website also contains a tool for designing a own snow fence.

MnDOT has used these tools and other promotional efforts to nearly double the number of farmers with contracts for corn rows enrolled in the Living Snow Fences program.

What’s next

The willow species recommended by researchers will be evaluated further in 2017 when they install it as a living snow fence on a new construction site on Highway 60 between Windom and Mountain Lake. Researchers also recommend a future study to compare volume of road salt use before and after installation. They also want to look into identifying appropriate buffer distances to keep willow roots from interfering with cropland root systems.

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