All posts by Shannon Fiecke

Marketing and Communications Manager, MnDOT Research Services
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.

Research

Newly funded studies tackle big transportation questions

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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

Materials & Construction

Environmental

Planning

Maintenance Operations

Traffic & Safety 

Traffic and Safety

Major Ramp Metering Upgrade Reduces Freeway Delays

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Motorists are experiencing less delay on metro-area highways, thanks to major changes to the Twin Cities’ ramp metering system.

The Minnesota Department of Transportation has reconfigured ramp meters to be more in sync with real conditions. With changes to the turn-on and turn-off criteria, the meters are actually running for a shorter period of time and are only activated when needed.

Ramp meters are traffic lights placed on freeway entrance ramps that control the frequency that vehicles can enter the highway. Sensors embedded in the pavement collect the vehicle traffic data used to time approximately 440 ramp meters.

Staff at the Regional Transportation Management Center, which manages the ramp meters, say the whole system is operating better because of changes that were implemented approximately one year ago (based off a 2012 study).

University of Minnesota-Duluth professor Eil Kwon developed the system’s new software algorithms. In a case study of Highway 100, he found that the delay on the mainline dropped by nearly half.

On northbound Highway 100, the amount of “delayed vehicle hours” — defined as the vehicle hours of traffic flow with speeds less than 45 mph — that motorists experienced dropped 48 percent during the months of October and November in 2012 when compared to the same period in 2011. During the same time period, total volume on that section of northbound Highway 100 increased by 2.7 percent, Kwon said. In spring 2013, the amount of delayed vehicle hours had been reduced by 17 percent.

These results are preliminary, as additional analysis is needed to determine if these results are typical throughout the system on other freeway corridors. However, based on a personal savings of $16.50 per hour, the scenario described above represents a cost savings to motorists of $1,353 to $3,447 per day (depending on the season). That’s as much as $339,150 to $861,640 per year for just a six-mile stretch of highway.

More efficient

Under the old system, each ramp meter would turn on based on current traffic conditions, but the criteria to turn on were easily met, causing the meters to turn on too soon. The old system did not have turn-off criteria, allowing meters to run until a pre-set time of day.

With the new system, improvements were made to make the meters respond more appropriately to current traffic conditions. The turn-on criteria were improved so that meters come on only when needed, and turn-off criteria were added, allowing meters to turn off when traffic conditions improved.

The new metering system is particularly effective at reducing the number of meters operating on light traffic days.

“On days like the ones leading up to Thanksgiving, where traffic may be 10-to-15 percent less than normal, instead of, say, 150 ramp meters being on at a particular time, now maybe only 50 ramp meters will be operating,” explained MnDOT Freeway System Operations Engineer Jesse Larson.

Upgrades to the ramp metering system also allow for a better picture of what traffic is like at a given moment, because it’s now based on corridor density rather than traffic flow.

Traffic flow is the measurement of the number of vehicles passing a given point. Using traffic flow was flawed, in that similar traffic flows can occur at different speeds. The old system couldn’t differentiate between 1,000 cars passing by at 20 miles per hour versus 1,000 cars passing at 60 miles per hour, for example.

Corridor density, on the other hand, is the number of vehicles per lane per mile. By measuring density instead of traffic flow, the system has a more accurate picture of what current conditions are like on the freeway.

Another bonus: ramp meters will no longer release a bunch of cars simultaneously once an entrance ramp fills up. That’s because the system can now detect the ramp filling up and release the extra cars gradually instead.

The amount of hours vehicles wait at entrance ramps fell by nearly 50 percent during the fall months along a section of Highway 100.
Twin Cities ramp meters now turn on and off based on live traffic conditions.

Related Resources

Development of Freeway Operational Strategies with IRIS-in-Loop Simulation study

Maintenance Operations

Road Surface Monitors Could Help Reduce Salt Usage

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MnDOT is testing a mobile road condition monitor that uses infrared technology to detect hazardous ice, snow or wet conditions without even touching the pavement.

Maintenance crews hope the device, called the High Sierra Surface Sentinel, could help them better determine when it’s time to apply salt when they’re plowing. The mobile sensor reports air temperature, surface temperature and road friction data.

“The biggest reason we’re looking at this is for the friction reading,” said MnDOT Salt Solutions Coordinator Joe Huneke. “Typically, when operators are patrolling their route and the road looks like it’s getting icy, they’ll err on the side of caution and apply salt — and it may not need it.”

The device being tested by snow and ice crews in northern Minnesota would also provide real-time surface weather conditions. Currently, plow operators and supervisors must enter road conditions into a computer or relay them by phone, a time-consuming process that operators are not always able to perform in a timely manner.

The biggest potential benefit, however, is lower salt consumption.

“Sometimes you get a light cold snow event where it might look like there’s a little ice on the road, but, in fact, you have good friction numbers and you don’t need salt. Once you put chemical down, you’re committed to it,” Huneke said.

District 1 snow and ice crews are evaluating the unit pictured below for its accuracy and effectiveness in determining slippery conditions. It will be compared with another device tested in District 3 that also uses infrared technology to determine how slippery the road is, and technology being tested in District 6 that uses gravitational force to determine the road surface friction.

MnDOT it testing a mobile surface condition sensor that provides real-time surface weather condition of roadways.
MnDOT it testing this mobile road condition sensor, which provides real-time surface weather condition of roadways.

Related Research

MnDOT’s Office of Maintenance has its own research program designed to let maintenance personnel test innovative ideas to keep our roads smooth, snow-free and safe. They even put out a monthly bulletin featuring new ideas and technologies. (You can find the back issues here.)

Other winter maintenance research projects are featured in MnDOT’s 2011-2013 Maintenance Operations Research Report  (PDF, 9 MB, 98 pages)

Traffic and Safety

Minnesota: Are You Ready to Mumble?

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In the search for a quieter rumble strip, Minnesota may have found a winner in California.

California’s standard rumble strip design outperformed Minnesota’s and Pennsylvania’s in a comparison study along a rural highway near Crookston, Minnesota. (Read the recently published report.)

“California’s rumble strip still gave significant feedback to drivers, but it was significantly less noticeable outside the vehicle,” said engineering consultant Ed Terhaar, who performed a noise analysis with acoustical engineer David Braslau on behalf of the Minnesota Local Road Research Board.

A California-style sinusoidal rumble strip, installed along a Polk County Highway.
A California-style sinusoidal rumble strip, installed along a Polk County Highway.

Although they serve as an effective warning to drivers, rumble strips can cause unwanted noise when a vehicle drifts over a centerline or edgeline.

Both the LRRB and the Minnesota Department of Transportation, which is sponsoring a companion study, are interested in finding a new design that still captures the driver’s attention, but minimizes the sound heard by neighboring residents.

Polk County tests

Terhaar and Braslau’s research showed that Minnesota and California’s designs produce a similar level of interior noise. Although external decibel levels are not that different from each other either, Minnesota’s rumble strip has a considerably stronger tone that can be heard further away.

“California’s sound is less sharp, less intrusive and less noticeable,” Braslau said. “Minnesota’s has a really sharp peak. So while the absolute sound level of California’s isn’t all that much lower, its perception is less.”

Testing was performed using three different vehicles – a passenger car, pickup truck and semi-trailer truck – at three different speeds – 30, 45 and 60 miles per hour.

In general, Pennsylvania’s rumble strip had both a quieter interior and exterior sound than California’s and Minnesota’s.

Like Pennsylvania, California’s rumble strip has what is called a sinusoidal design – a continuous wave pattern that’s ground into the pavement (it’s the style commonly used in Europe and has been called a “mumble strip” because it’s quieter). The main difference between the two is that California’s wave length is 14 inches, while Pennsylvania’s is 24 inches.

Minnesota’s design is much different than the sinusoidal pattern used by the other two states.

“It’s not a continuous wave – it’s basically chunks of pavement taken out at certain intervals with flat pavement in between. It’s more of an abrupt design, whereas California and Pennsylvania’s are more continuous and smooth,” Terhaar explained.

The next step for researchers is to test variations of the California rumble strip design at MnDOT’s Road Research Facility (MnROAD).

The 8-inch rumble strip tested in Crookston is the typical edgeline design used by Polk County, but it was found to be too narrow for semi tires, so MnDOT will look at wider designs in its follow-up study. Researchers will also look at the impacts to motorcyclists and bicyclists, as well as the California rumble strip’s centerline striping capability.

The Minnesota rumble strip, left, and California rumble strip, right.
The Minnesota rumble strip, at left and also pictured in top photo, and California rumble strip, right.

Related Resources

Rumble Strip Noise Evaluation study

MnDOT looks for solution to noisy highway rumble strips – Crossroads article

Traffic and Safety

MnDOT Tests Crowdsourcing to Improve Road Condition Reporting

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The Minnesota Department of Transportation is testing a crowdsourcing application that will allow motorists to update winter weather road conditions on the state’s 511 system.

The Regional Transportation Management Center is planning a soft launch of Citizen Reporting in April, initially inviting MnDOT employees to post their experiences on routes they travel.  By next winter, the RTMC hopes to invite the public to do the same.

“We suspect that citizen reporters will be similar in ethic to the kinds of people who volunteer to be weather spotters,” said MnDOT Transportation Program Specialist Mary Meinert, who assists with day-to-day operations of 511.

511 Citizen Reporting
Iowa launched Citizen Reporting in November. Here is an example of a citizen report.

Currently,  MnDOT maintenance crews report road conditions, but Greater Minnesota lacks 24/7 coverage and its reports can become quickly outdated, especially on highways that aren’t plowed as frequently or lack traffic cameras, said 511 System Coordinator Kelly Kennedy Braunig.

Citizen reporting, especially on weekends, will help keep that information fresh.

“We try to explain on the website that we only update from 3–6 a.m., 3–6 p.m. Monday through Friday and as road conditions change, but we still get many emails requesting more frequent road condition information,” Braunig said.

Even a recent comment on MnDOT’s Facebook page pointed out the limitations in one area of the state: “Updates [only] come during government work hours.”

Growing Service

It’s actually a welcome sign that the public wants more from 511.

Seven years ago, when Braunig applied for her job, not many people used 511. In fact, at the time, she wasn’t even aware of the service, which provides information to travelers on weather-related road conditions, construction and congestion.

Today, 511’s online program and mobile app are accessed by more than 5,000 people per day during the winter (and about half as many during the summer). Data comes from MnDOT’s construction and maintenance offices, as well as state trooper data and incident response. This real-time information is available for all of Minnesota.

In the Twin Cities metro area, more than 700 traffic cameras allow MnDOT and State Patrol dispatchers to check the condition of 170 miles of highways and monitor traffic incidents at any time. Rochester, Duluth, Mankato and Owatonna also have cameras for incident management and traffic monitoring.

The 511 system’s greatest challenge is in Greater Minnesota, where road condition information is used daily by schools, ambulance personnel and truckers, as well as the traveling public, but information isn’t updated frequently outside of business hours.  Citizen reporting will be a beneficial resource.

Other states

Other northern states face similar challenges as Minnesota, but have been able to improve the timeliness of road condition data with assistance from truckers and other motorists.

In Wyoming, more than 400 citizen reporters (primarily truckers) call in road conditions to the Transportation Management Center. In Idaho, citizen reporters directly put the information into the 511 system. Minnesota will be the fifth state to adopt citizen reporting, following Iowa, which launched its service in November 2014.

Like Iowa, Minnesota’s citizen reporting will initially focus on winter roads.

To participate, people will need to take an online training module and then register their common routes, perhaps the highways they take to work or their way to the cabin on the weekends. These contributions will be marked as a citizen report on the website.

“Minnesota truck drivers are loyal users of the 511 system and we suspect they will also make some of our best reporters,” Meinert said.

Minnesota is part of a 13-state consortium that shares a 511 service technology provider. States with citizen reporting recently shared their experiences in a Peer Exchange sponsored by North/West Passage, a transportation pooled fund that is developing ways to share 511 data across state lines.

“With citizen reporting we hope to give people a voice and a chance to participate,” Braunig said.

Maintenance Operations

MnDOT Plow Drivers Invent New, Hybrid Plow Design

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If the plow pictured above looks like two different plows welded together, it’s because they are.

Minnesota Department of Transportation snow plow operators in southwestern Minnesota have invented an experimental plow that uses the wind to cast snow from the road without impeding traffic or the operator’s view.

Manufactured for MnDOT by Fall Plows, the plow incorporates half of a traditional bull-dozer style plow with half of a Batwing-style plow.  It eliminates the large “ear” on the driver’s side of a Batwing style plow that can stick out into oncoming traffic during center-line snow removal.

Half of the reversible batwing-style plow, pictured at left, was combined with half of the reversible bulldozer-style plow, pictured at right.
Half of the reversible batwing-style plow, pictured at left, was combined with half of the reversible bulldozer-style plow, at right.

District 8 Willmar Maintenance Supervisor Dennis Marty said he was looking for a reversible-style plow that could be used in the heavy winds and reduced visibility from blowing snow that are prevalent in western Minnesota.

When drivers are plowing against a northwest wind in rural Minnesota, the snow coming out of the chute will sweep across the truck and blind drivers, so operators needed a plow with a reversible system so they could throw the snow with the wind.

While an express plow with chutes on both ends (batwing-style), pictured above at left, was great for throwing snow to the right, when snow plow drivers took it down narrow two-lane roads, the plow stuck 2.5 feet into the oncoming lane and its big barrel partially blocked the headlights and the operator’s view.

So operators tried a regular one-way plow (pictured below), which resembles a funnel laid on it side, and put it on a reversible system that would allow operators to turn the plow both directions, so it could throw snow to the right or the left. However, this plow couldn’t blow snow high enough to the left, so snow piled in the left traffic lane.

One-way reversible plow.
One-way reversible plow.

Marty said he spent four to five years looking for a plow that combined the batwing and bull-dozer designs, but he couldn’t find anything sturdy and maintenance-free enough. Finally, he and Maintenance Research Program Administrator Ryan Otte sat down with Falls Plows in Little Falls, Minnesota and asked the company to build one.

The plow will be useful on low-volume roads that have little traffic during the middle of the night, which allows plow operators to cast the snow with the wind.

The Willmar office began using the experimental plow last winter and will be replacing all of its plows with it. Snow plow drivers from other areas of the state have been so impressed that at least two other maintenance districts have also ordered them.

Related Research

MnDOT’s Office of Maintenance has its own research program designed to let maintenance personnel test innovative ideas to keep our roads smooth, snow-free and safe. They even put out a monthly bulletin featuring new ideas and technologies. (You can find the back issues here.)

Other winter maintenance research projects are featured in MnDOT’s 2011-2013 Maintenance Operations Research Report  (PDF, 9 MB, 98 pages)

Traffic and Safety

Making SMART Signals even smarter

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Your drive home may be a few minutes quicker today thanks to a team of researchers who are making it easier for Minnesota engineers to retime traffic signals.

It normally costs $3,500 to retime a signal due to the time involved in collecting the data and optimizing timings. But over the past several years,  MnDOT-funded research has helped develop the SMART Signal system, which not only collects traffic and signal-phase data automatically, but also identifies under-performing traffic signals and generates optimal signal timing plans with minimal human intervention.

Traffic delays typically grow 3 to 5 percent per year due to outdated signal timing; however, most traffic signals in the United States are only re-timed every two to five years (or longer).

“Large-scale deployment of the SMART Signal system will significantly change the state-of-the-practice on signal re-timing because MnDOT won’t have to retime a traffic signal based on a fixed schedule,” said University of Michigan researcher Henry Liu (formerly a University of Minnesota professor), who began developing the system in the mid-2000s. “Instead, because of the reduced cost of signal data collection and performance measurement, signal retiming becomes performance-driven rather than schedule-based.”

You can view the traffic monitoring on corridors with SMART-Signal systems on this website, http://dotapp7.dot.state.mn.us/smartsignal/.

MnDOT (along with many cities and counties) embeds loop detectors in road pavements that notify a traffic signal that a vehicle is present. Staff normally must manually track wait times to determine how the signal timing is affecting traffic.

But SMART Signal automates much of this process by recording how long a vehicle waits at an intersection and automatically reporting the data (along with signal timing) to a central server. The data — viewable in real-time on this website  — can then be analyzed to determine traffic patterns and optimal signal timing.

Recent enhancements to the SMART Signal system were successfully tested on Highway 13 in Burnsville, reducing vehicle delay there by 5 percent.  The benefit could be in the double digits for corridors with worse traffic delays.

SMART Signal — which stands for Systemic Monitoring of Arterial Road Traffic — has been installed at more than 100 Minnesota intersections and is currently in the process of commercialization.

The latest research optimizes the system’s ability to reduce traffic delays by developing a framework to diagnose problems that cause delays at traffic signals and an algorithm that automatically optimizes the signal plan to address these problems. The software upgrade has since been integrated into all SMART Signal intersections.

Across the country, the financial benefit of retiming signals has been shown to be tremendous. On San Jose Boulevard in Jacksonville, Florida, for instance, traffic delays in one corridor dropped 35 percent and resulted in an annual estimated fuel savings of $2.5 million.*

“Data collection and performance monitoring are critical for improving traffic signal operations, and yet before the development of the SMART Signal system, these tasks were prohibitively expensive for most agencies because of the number of signals involved,” Liu said.

Future Applications

Liu is also looking at other potential applications for SMART Signal :

  • Improving safety at intersections with unusually high crash rates and predicting which intersections are likely to have elevated crash rates in the future.
  • Developing traffic signal timing models for diverging diamond intersections.
  • Determining how traffic and vehicle routes are affected by construction lane closures and detours on signalized highways.

A real-time adaptive signal control, which would automatically adjust signal timings based on current conditions, is not currently feasible with the SMART Signal system because it would require additional vehicle sensors. The latest SMART Signal research does, however, automate the data collection and calculations that would help the development of such a system.

Data collection
A data collection unit collects event-based traffic and signal data and sends it to a remote center for analysis.

*The Benefits of Retiming Signals,” ITE Journal, April 2004

Note: This blog post was adapted from an article in the latest issue of our newsletter, Accelerator. Click here to subscribe.

Related Resources

Research Project: Automatic Generation of Traffic Signal Timing Plan (2015)

(Development of the SMART-SIGNAL system began with Real-Time Arterial Performance Monitoring System Using Traffic Data Available from Existing Signal Systems (2009). It continued with Research Implementation of the SMART SIGNAL System on Highway 13 (2013) , which refined the system and its user interface, and Improving Traffic Signal Operations for Integrated Corridor Management (2013), which developed data-based strategies for relieving congestion by adjusting signal timings.)

Bridges and Structures

Using History to Predict Bridge Deck Deterioration

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Just how long will it be before a bridge deck needs to be rehabilitated?  Why not look to history to find out?

Researchers have put several decades of MnDOT bridge inspection records to good use by analyzing old bridge deck condition reports to calculate how quickly similar bridge decks will deteriorate.

MnDOT inspects bridges regularly, but had never used this historical data to help determine the rate of bridge deck deterioration and what factors influence it.

“We’re always trying to improve the timing of bridge deck repair projects and improve our understanding of what contributors affect the way our bridge decks deteriorate,” said Dustin Thomas, MnDOT’s South Region Bridge Construction Engineer.

Data-Crunching

From their analysis, researchers created deterioration tables that can be used to better predict the timing and costs of repairs and maintenance.

Researchers looked at the inspection history and construction details of 2,601 bridges to determine the impact of factors such as type of deck reinforcement, depth of reinforcement below the driving surface, traffic levels and bridge location.

Using the inspection data, researchers developed curves that show how long a bridge deck is likely to stay at a given condition before dropping to the next. They developed separate curves for each variable that had a significant impact on deck deterioration rates.

What They Found

Several factors were found to have a notable impact on how quickly bridge decks deteriorate:

  • Decks without epoxy-coated bars built between 1975 and 1989 deteriorate more quickly than other bridge decks.
  • Bridges with less traffic showed slightly slower rates of deterioration than highly traveled bridges.
  • Metro area bridges drop to a condition code of 7 (good) more quickly than bridges in other parts of the state. This may be due to increased chemical deicer usage or because maintenance activities like crack-sealing are more likely to be delayed on larger metro bridges  because of the difficulty accessing middle lanes.
  • When a new deck is installed on an existing bridge, the deck performs like a brand-new bridge and so MnDOT should use the deterioration table for the re-decking year, rather than the year the bridge was originally constructed.

MnDOT plans to incorporate future bridge inspections into the dataset to enhance the predictive value of the deterioration tables.

Related Resources

The impact of overlays on bridge deck deterioration in Minnesota was not clear, but redecked bridges were found to perform similarly as brand-new decks.
Materials and Construction

MnDOT, Alabama center team up for national pavement research

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The nation’s two largest pavement test tracks are planning their first-ever co-experiments.

The Minnesota Department of Transportation’s Road Research Facility (MnROAD) and the National Center for Asphalt Technology (NCAT) began discussing a formal partnership last year and have now asked states to join a pair of three-year research projects that will begin this summer.

Representatives of the test tracks are meeting next week in Minneapolis at the 19th Annual TERRA Pavement Conference. They said the partnership will develop a national hot mix asphalt cracking performance test and expand the scope of existing pavement preservation research at the NCAT facility in Auburn, Alabama, to  include northern test sections in Minnesota.

MnROAD plans to build test sections at its facility and also off-site on a low- and high-volume road, which may include concrete test sections if funding allows. These Minnesota test sections will supplement 25 test sections built by NCAT on an existing low-volume haul route in 2010 and an off-site high-volume test road planned for this summer in Alabama to assess the life-extending benefits of different pavement preservation methods. Both agencies have also been developing performance tests to predict the cracking potential of asphalt mixes, and they will now work together on that research as well.

“We will collect and analyze the data in similar ways, and I think we’ll have a greater appeal nationally, as we cover a range of climate conditions,” said MnROAD Operations Engineer Ben Worel.

Participation in the pavement preservation study is $120,000 per year for the initial research cycle, which will drop to $40,000 after three years; the cracking study will run three years at $210,000 per year.  Alabama will be the lead state for this effort.

State departments of transportation are asked for commitment letters this month if they are interested in joining either study, even if they do not have SP&R (State Planning and Research) dollars available at the time. Participating agencies will get to design the scope of the research and be kept advised of the ongoing findings, so they can benefit early from the project. Initial planning meetings will be done through a series of webinars in March and April of this year with participating agencies.

At a January 8 webinar, speakers said the research will help states determine how long pavement preservation treatments will last.

“Many DOTs have really well-designed and well-thought-out decision trees, where they can take pavement management data and end up with a rational selection of pavement alternatives. But the issue of extending pavement life is the really big unknown, because references provide a broad range of expected performance,”  NCAT Test Track Manager Buzz Powell said.

Another benefit is that states can learn how pavement treatments hold up in both hot and cold climates.

“It’s 14 degrees right now in Mississippi. It rains about every three days, freezes and then thaws,” said Mississippi Chief Engineer Mark McConnell. “So we need to know how pavement preservation is going to work in the north as well.”

For additional information, contact Ben Worel (ben.worel@state.mn.us) at MnROAD or Buzz Powell (buzz@auburn.edu) at NCAT.

mnroad_ncat
Aerial views of the pavement test tracks at MnROAD (left) and NCAT (right).