Minnesota: Are You Ready to Mumble?

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

MnDOT Tests Crowdsourcing to Improve Road Condition Reporting

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.

MnDOT Plow Drivers Invent New, Hybrid Plow Design

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 and 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)

Making SMART Signals even smarter

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.)

Travel behavior study shows drivers are spending less time traveling

Something unprecedented has happened to Americans’ travel patterns. Even before the recent recession, total distance traveled per person had started to decline, and the rate of total vehicle travel had begun to steadily decrease as well.

In a new five-part series of research reports sponsored by MnDOT and the Metropolitan Council, University of Minnesota researchers are delving into a set of rich data encompassing more than four decades of travel behavior surveys to enable the region’s transportation planners to better understand how its residents make decisions about whether, when, where, and why to travel.

In the first study, researchers examined how changes in the accessibility of destinations—such as jobs, shopping, and leisure activities—have changed travel behavior in the past 20 years.

“We started with a detailed analysis of travel surveys conducted by the Metropolitan Council in 1990, 2000, and 2010,” says David Levinson, the study’s principal investigator and RP Braun/CTS Chair in the Department of Civil, Environmental, and Geo- Engineering. “We found that people are spending slightly less time in motion and more time at home. We also found that accessibility is a significant factor in determining not only travel behavior but overall time budgeting in general. In short, each person has to decide how they will use the time allotted to them each day, and many of those decisions are directly related to the transportation and land-use systems in place.”

A deeper look into the data sheds additional light on the relationship between accessibility and travel behavior. For example, trip durations for workers have gone up for all activities between 1990 and 2010. More noticeably, distances for trips have increased markedly: workers take jobs farther from their homes and shop farther from their homes. Travel speeds also increased for the average worker, due to more travel on faster suburban roadways that carry a larger share of all travel. In contrast, for non-workers, trip durations and overall travel time have gone down.

“Interestingly, although time, distance, and speed per trip has generally risen for workers, the number of those trips is declining,” Levinson says. “As a result, overall, fewer miles are being traveled and less time is being allocated to travel.”

Total time spent shopping also decreased for workers and for males, likely caused in part by an increase in online commerce. “The Internet has provided electronic accessibility, much as the transportation network has in the material world,” Levinson explains. “It helps to facilitate commerce, communication, education, and leisure. This may lead to a decreased need for people to travel, and account for more time spent at home.”

Jonathan Ehrlich, planning analyst with the Metropolitan Council, says the research “helps us get more value from our travel surveys and will aid in understanding how travel is changing, and what the risks are in the assumptions and models we use for planning and forecasting.”

The findings will prove useful not just for Twin Cities transportation planners but for planners and engineers worldwide. “Our models can be easily adapted to data from other cities or for other activities besides work,” Levinson says. “This creates an approach that can be used to gauge the impact of a transportation project from an accessibility standpoint and determine how that project will translate into time allocation.”

Other parts of the study will look at changes in telecommuting behavior over time, the effect of transit quality of service on people’s activity choices and time allocation, changes in travel behavior by age cohort, and analysis of bicycling and walking in light of land-use and transportation system changes.

Crossroads will feature coverage of these projects as they are completed.

Using History to Predict Bridge Deck Deterioration

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.

Winter seminars highlight research on work-zone safety, culvert design, and more

Join us in person on the U of M campus or tune in online to the CTS winter research seminars. The seminars will highlight a sampling of the latest transportation research at the U of M.

Here’s this year’s seminar schedule:

Each seminar will be held in Room 50B at the Humphrey School of Public Affairs. Or, if you can’t make it in person, you can watch the seminars live online or view recordings posted after the events. For details about the live broadcasts, see the individual seminar web pages.

There’s no cost to attend, and each seminar qualifies for one Professional Development Hour.

Hope to see you there!

MnDOT, Alabama center team up for national pavement research

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).

Study reveals how Minnesota industries rely on transportation

Results of a newly released MnDOT research report shed new light on the role transportation plays in our state’s economic competitiveness, and highlight the unique challenges faced by some of the state’s major industry clusters.

The report, authored by Professor Lee Munnich of the University of Minnesota’s Humphrey School of Public Affairs, underscores the importance of a reliable transportation system in facilitating economic growth. Munnich examined the impact of transportation on Minnesota’s competitive industry clusters — geographically concentrated, interconnected groups of companies and institutions that share knowledge networks, supply chains and specialized labor pools.

MnDOT Research Project Engineer Bruce Holdhusen said MnDOT’s goal with the study was to discover how its investment decisions could help support job creation and economic prosperity.

“The idea is to look at the companies and industries that are already bringing money into the state, figure out what their transportation challenges are, and then use that information to see what kind of investments we could make to support their continued growth,” Holdhusen said.

MnDOT is incorporating the results of the study into its statewide freight planning. The industry clusters-approach also is being used by MnDOT in a statewide effort to talk with manufacturers, other shippers, and carriers about their transportation priorities and challenges.  MnDOT will focus on its Metro District starting this summer.  Two similar projects have been undertaken in Greater Minnesota, with a third study starting later this year. (Results from one study, in southwest Minnesota/District 8, are available online.)

The full report is available online, and examines a wide range of industries, including forest products, medical devices, robotics and processed foods. We’ve pulled out a few interesting tidbits below.

Recreational Vehicles (Northwest Minnesota)

A semi truck driving on a snowy highway.
Minnesota winters are great for snowmobiling, but not always great for shipping snowmobiles. (Photo by Dave Gonzalez, MnDOT)

As noted in the report, Minnesota’s extreme winter weather poses unique challenges to its economic competitiveness. Ironically, nowhere is this more evident than in the state’s snowmobile-producing northwest corner.

Polaris and Arctic Cat (together with smaller, more specialized firms like Mattracks) employ thousands of Minnesotans, producing a wide variety of recreational vehicles and accessories that are sold and distributed all over the world. While the companies’ snowmobiles might fare well in a blizzard, the trucks that deliver them don’t. A bad snowstorm can cause delays in both supply and product shipments; it can also prevent employees from getting to work, or even shut down a plant altogether. On a larger scale, these issues make it difficult for the companies to expand at their ideal rates.

The report notes that MnDOT’s 511 system is an important source for many companies to identify and respond to potential shipping delays. It recommends continuous improvements to the system.

The Mayo Clinic (Rochester Area)

Metal FedEx containers at an airport.
Air carriers like FedEx have limited capacity for refrigerated shipments, which creates challenges for shipping medical lab samples. (Photo by Dave Gonzalez, MnDOT)

The Mayo Clinic has become synonymous with the Rochester metropolitan area, and for good reason: it employs 37,000 residents and brings in 500,000 unique patients each year from all 50 U.S. states and 150 countries. As you might imagine, generating that much activity in a community of only 110,000 people creates some unique and significant transportation challenges.

Unlike most competitor institutions (Johns Hopkins in Baltimore, for example), the Mayo clinic is located in a relatively small metropolitan area. The local airport has an older navigation system and offers less direct commercial air service. As a result, it depends on high-quality transit and freight service to help accommodate the constant flow of visitors and supplies. The shipping of highly perishable lab samples is also a challenge, as air carriers have limited capacity for refrigeration. Finally, adverse weather conditions can affect emergency services dispatchers’ ability to send fast modes of transportation such as helicopters.

Hospitality and Tourism (Brainerd Lakes Area)

Boats docked on a lake at dawn.
Lakeside resorts a great way to enjoy Minnesota’s scenic beauty — but getting there can be a challenge. (Photo by Dave Gonzalez, MnDOT)

The oil boom in North Dakota has generated a lot of wealth in a short amount of time, and resorts like the Grand View Lodge in Nisswa would love to capture some of it by enticing new vacationers from the west. The trouble is, the area is inconvenient to reach from that direction.

A four-lane highway makes it easy for visitors from St. Cloud or the Twin Cities to visit resorts in the Brainerd area, but travelers coming from the Dakotas face a more circuitous route. Air travel options help to an extent, as visitors from even farther distances can fly into Fargo and then drive in from there. St. Cloud also has daily air service from Chicago, which helps maintain a constant flow of visitors.

Related Materials

New Tool Measures Impact of Heavy Trucks

A new tool developed by the Local Road Research Board helps cities and counties assess how much increased heavy vehicle traffic affects local roads.

Researchers created an analysis method and corresponding spreadsheet tool that city and county engineers can use to calculate the impact of heavy vehicles on asphalt roads beyond what was planned in the original pavement design.

The information will help agencies optimize services, such as garbage collection, for the least amount of damage. It will also help agencies better plan roads in new developments, as well as redesign existing roads that are nearing the end of their lives.

Lack of Data

Heavy trucks cause local roads to deteriorate more quickly than passenger vehicles, but it is challenging to quantify the impacts, especially for areas where traffic was not forecast at the time a road was designed.

Many local engineers in Minnesota have requested information about the impact of heavy vehicles in light of new construction, commercial distribution facilities and hauling routes. This information is needed to assist in local road planning and maintenance.

Two Methods

In a newly completed study, investigators developed two methods for calculating heavy vehicle impact:

  • Calculate the additional bituminous material (and associated costs) that would have been required to construct the pavement had the heavy truck traffic been predicted when the pavement was designed.
  • Calculate the portion of a pavement’s design life, measured in equivalent single-axle loads (ESALs), consumed by unanticipated vehicles.

“Before this project, there wasn’t an easy way for an engineer to determine how much a specific truck was going to decrease the life of a road,” said  Deb Heiser, Engineering Director, City of St. Louis Park.

Whereas previous research has calculated the impact of extremely heavy vehicles over the short-term (typically the course of a construction project), this project calculates the impact of long-term increases in traffic from vehicles that are heavy, but still mostly within normal legal weight limits.

The tool can be used for a single street segment or an entire road network. Users can also compare current situations with proposed ones to evaluate the impact of potential changes in heavy traffic levels.

Related Resources

Minnesota transportation research blog

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