Research

‘Smart window’ technology opens new possibilities for transportation noise control

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Nearly every time a highway or airport expansion is proposed, transportation planners face opposition from residents who fear the increased noise levels in their homes and businesses. Traffic noise is often mitigated with physical noise barriers, but the large, thick walls often draw opposition as well.

A new technology developed by University
 of Minnesota mechanical engineering professor 
Rajesh Rajamani as part of 
a research project funded
 by the National Science
 Foundation could soon
 provide a nearly invisible
 solution for transportation 
noise cancellation—and 
give transportation planners another tool for overcoming project opposition.

Noise enters homes close to airports and highways primarily through windows, and windows can transmit ten times the sound energy as walls can, says Rajamani. With this in mind, researchers set out to reduce the amount of transportation noise transmitted through windows.

To accomplish this goal, researchers created a method of active noise control for windows. Active noise control works by using speakers to generate a sound wave that is a mirror image of the undesirable sound wave. Superimposing an “anti-noise” wave of the same amplitude as the undesirable noise wave results in a reduced decibel level of noise in the environment.

The research team began by designing thin, transparent speaker panels to fit in the empty space between the two panes of a double-pane window. Then, the researchers tested the effectiveness of the new speakers, using them to cancel out undesirable transportation noise from outside the home while preserving the desirable noise from inside the home.

In addition to mitigating traffic noise, this new technology offers other surprising benefits. Researchers have found that the “smart window” speakers can actually be used as home audio speakers without losing any of their noise-control benefits.

Read the full article in the February issue of Catalyst.

Bicycling, Traffic and Safety

Three common questions about bike lanes, answered

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If you’ve ever driven near a bike lane and not known what to do, you’re not alone.

A forthcoming video from the Local Road Research Board seeks to answer common questions about on-street bike lanes and help bicyclists and motorists better understand the rules. The video is due to be released this spring; in the meantime, we thought we’d give you a sneak preview by addressing three common misconceptions about bike lane rules and safety. 

1) Are bicyclists required to use a bike lane, when present?

No. Although bike lanes usually provide the smoothest, safest and most efficient method of transportation — for everybody — they are not required to use them. They are allowed to ride outside bike lanes to make turns or avoid debris, and they still have the option of using an adjacent trail where available.

2) Are vehicles allowed to enter bike lanes?

Yes, but only to park or turn onto a driveway or street. Motorists should treat bike lanes like any other lane of traffic and yield to approaching bicyclists, but they do have the right to enter bike lanes when turning.

3) Do bicyclists have to follow the same rules as motorists?

Yes. Bicycles are considered vehicles under Minnesota state law and have the same rights and responsibilities. Cyclists are required to obey stop signs and signal their turns, just like motorists.

A federal project funded 75 miles of new bike lanes in four communities, including Minneapolis.
A recent federal project funded 75 miles of new bike lanes in four communities, including the city of Minneapolis. Biking in these areas increased 50 percent; 7,700 fewer tons of carbon dioxide were emitted and gas consumption was reduced by 1.2 million gallons. (Source)

Watch for the LRRB’s new bike safety video on Crossroads this spring. In the meantime, check out MnDOT’s tips on bicycle safety.

Freight and Railroads, Traffic and Safety

Demonstration project helps truck drivers find safe places to park

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With freight traffic increasing on U.S. roadways, commercial truck drivers often struggle to find safe and legal places to park. If parking spaces are not available at a nearby rest area or truck stop, drivers may be forced to pull over in unsafe locations or continue driving and become dangerously fatigued. Drivers may also risk violating federal hours-of-service rules, which require them to rest after 11 hours of driving.

In response to this issue, a team from MnDOT, the University of Minnesota, and the American Transportation Research Institute
 is developing a system that can identify available truck parking spaces and communicate the information to drivers—helping them determine when and where to stop. System benefits include improved safety, reduced driver fatigue, and better trip management.

The system uses a network of digital cameras suspended above a parking area to monitor space availability. Image processing software developed by researchers at the U of M’s computer science and engineering department analyzes the video frames and determines the number of available spaces.

As part of a demonstration project funded by MnDOT and the Federal Highway Administration, the project team is installing the system at three MnDOT rest areas and one private truck stop on I-94 west and northwest of the Twin Cities.

The U of M research team first installed the system in late 2012 at the the Elm Creek Rest Area, two miles north of Interstate 494 on I-94. As of early 2014, the system has been installed at an additional rest area, and a third site is in progress.

Next steps for the project include implementing several mechanisms that will communicate parking information to truck drivers. First, the team plans to install variable message signs along I-94 this spring. Also in the works are an in-cab messaging system and a website.

Overall results of the demonstration project will help the team determine whether this technology holds promise for use in other corridors throughout the nation.

Read the full article in the February issue of Catalyst.

Materials and Construction, Research

Innovative pavement textures reduce noise, improve fuel economy

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What if something as simple as changing the texture of the pavements we drive on could not only increase safety, but also reduce noise pollution and boost our vehicles’ fuel economy?

It’s possible, according to the latest research from MnROAD, the state’s one-of-a-kind pavement research facility. In a new report, investigators detail how quieter pavement textures, such as those applied by grinding grooves into pavements with diamond-coated saw blades (see the photo above), may also reduce rolling resistance — the force that resists a tire as it moves across the pavement’s surface.

The potential benefits to the public are significant. A 10-percent reduction in rolling resistance could reduce the U.S. public’s fuel consumption by 2–3 percent, eliminate up to $12.5 billion in fuel costs each year (as well as cutting carbon emissions). Add on the cost savings from reducing noise pollution (building noise barriers along highways can cost as much as $3 million per mile), and it’s clearly a win-win situation.

In the study, researchers used an innovative line-laser profiler to develop three-dimensional representations of test pavement surface textures. They then investigated the relationship between these surface characteristics and data on rolling resistance that was collected during a 2011 study using a special test trailer developed by researchers in Poland. This year, the same trailer will be used to conduct a second round of rolling resistance measurements at MnROAD.

The research is related to an ongoing pooled-fund study on concrete pavement surface characteristics. The goal is to produce data that will allow MnDOT to identify ideal ranges for surface characteristics that improve pavements’ quietness and ride quality while keeping them safe and durable.

Learn more
Researchers relied on rolling resistance data from a study conducted in 2011 with a test trailer developed by the Technical University of Gdańsk, Poland. This was the first time such measurements were taken in the United States.
Researchers relied on rolling resistance data from a study conducted in 2011 with a test trailer developed by the Technical University of Gdańsk, Poland. This was the first time such measurements were taken in the United States.
Materials and Construction, Research

MnROAD earns concrete pavement association award

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Staff from MnROAD, the Minnesota Department of Transportation’s cold weather road research facility in Albertville, Minn., were presented with the Marlin J. Knutson Award for Technical Achievement by the American Concrete Pavement Association in December.

The award cites the facility’s well-deserved reputation for being a place where both agency and industry ideas are put to the test. This award was presented as a tribute to the agency’s commitment to learning and putting ideas into practice.

The Marlin J. Knutson Award for Technical Achievement is presented to an individual or group who has made significant contributions to advance the development and implementation of technical innovations and best practices in the design and construction of concrete pavements.

(far right) Gerald Voigt, ACPA president and CEO, presented MnDOT with the Marlin J. Knutson Award for Technical Achievement during a ceremony in December. Receiving the award are (from left) Luke Johanneck, Bernard Izevbekhai, Roger Olson, Tom Burnham, Glenn Engstrom, Maureen Jensen and Sue Mulvihill. (Photo courtesy of the ACPA)
(Far right) Gerald Voigt, ACPA president and CEO, presented MnDOT with the Marlin J. Knutson Award for Technical Achievement. Receiving the award are (from left) Luke Johanneck, Bernard Izevbekhai, Roger Olson, Tom Burnham, Glenn Engstrom, Maureen Jensen and Sue Mulvihill. (Photo courtesy of the ACPA)

“MnROAD is helping to make roads last longer, perform better, cost less, construct faster, and have minimal impact on the environment,” said Gerald Voigt, ACPA president and CEO. “It is a model for other agencies to follow.”

MnROAD is a pavement test track initially constructed between 1991-1993. It uses various research materials and pavements and finds ways to make roads last longer, perform better, cost less to build and maintain, be built faster and have minimal impact on the environment. MnROAD consists of two unique road segments located next to Interstate 94.

Staff from the MnROAD facility in Albertville were recognized during the ACPA’s Distinguished Service and Recognition Awards ceremony in December. (Photo by David Gonzalez)
Staff from the MnROAD facility in Albertville were recognized during the ACPA’s Distinguished Service and Recognition Awards ceremony in December. (Photo by David Gonzalez)

This article, authored by Rich Kemp, originally appeared in Newsline, MnDOT’s employee newsletter. 

Policy and Planning, Public Transit, Research

Do streetcars support commercial development? New Orleans results say yes

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New streetcar lines are in the planning stages in Minneapolis and St. Paul. Proponents cite not only the lines’ ability to strengthen the transit system, but also their potential as catalysts for development. Estimating the impacts of streetcars is challenging, however, as most U.S. lines operate in downtown areas with many interrelated factors at play. A recent U of M research project examined the issue through the prism of one city’s experience: post-Katrina New Orleans.

The team—research fellow Andrew Guthrie and Assistant Professor Yingling Fan of the Humphrey School of Public Affairs—analyzed building permits near streetcar stops in the downtown business district and in several urban neighborhoods.

“Hurricane Katrina allowed—or required—more redevelopment to occur at a faster pace than 
normal, potentially allowing existing streetcar lines’ latent development impacts to appear,” Guthrie says. “This created an unfortunate yet rare opportunity for study.”

streetcars

The researchers estimated how the frequency of commercial and residential permits changed with distance from streetcar stops, controlling for hurricane damage, proximity to existing commercial areas, and pre-Katrina demographics.

They found that throughout the system, building permits strongly reflect the distance to stops—and that commercial and residential permits move
 in opposite directions within the first 750 feet.

Commercial permits declined the further away the location was from a stop. In residential areas, commercial permits show variation depending on neighborhood characteristics. The number of neighborhood residential permits rose about 24 percent with every 100 feet from a stop.

Based on their results, Guthrie and Fan conclude that traditional streetcar lines can help increase commercial development not just in downtown business districts, but in other urban areas as well. The findings also indicate that streetcars
 shape development in urban neighborhoods in
 a fundamentally different fashion than light rail.

Read the full article in the January issue of Catalyst.

Bicycling, Policy and Planning, Research

Exploring Nice Ride job accessibility and station choice

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Although bike share systems are becoming more popular across the United States, little is known about how people make decisions when integrating these systems into their daily travel.

In a study funded by CTS, researchers from the U of M’s civil engineering department investigated how people use the Nice Ride bike share system in Minneapolis and St. Paul. The researchers examined how Nice Ride affects accessibility to jobs and developed a model to predict station choice.

In the first part of the study, the researchers created maps showing accessibility to jobs by census block for both Nice Ride and walking—as well as the difference between the two—at time thresholds ranging from 5 to 55 minutes.

Overall, in blocks with both Nice Ride and walking job accessibility, Nice Ride provides access to 0.5 to 3.21 times as many jobs as walking.

By comparing Nice Ride to walking, the study demonstrated that walking can successfully be used as a baseline to show how a bike share system improves job accessibility. The results also pinpointed when and where Nice Ride had the strongest accessibility advantage over walking.

“This type of information can be used by bike share system planners to identify where new stations could be built to maximize their impact on job accessibility,” says grad student Jessica Schoner, a member of the research team.

In addition, the team developed a theoretical model for bike share station choice. The model considers users’ choice of a station based on their preference 
for the amount of time spent walking, deviation from the shortest path (the closest station may not be in the direct path of the person’s destination), and station amenities and neighborhood characteristics.

Findings show that people generally prefer to use stations that don’t require long detours to reach, but a station’s surroundings also play an important role. Results also indicate that commuters value shorter trips and tend to choose stations that minimize overall travel time.

According to Schoner, understanding people’s station preference can help provide guidance to planners that want to expand or optimize a bike share system.

Read the full article in the January issue of Catalyst.

Minnesota's transportation research blog