Category Archives: Research

General research posts.

Research, Traffic and Safety

Applying LiDAR to county transportation systems

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A handful of county highway department employees in the Rochester area gathered recently at the Olmsted County Public Works Service Center for a presentation and live demonstration by University of Minnesota Research Fellow Brian Davis about his team’s work involving light detection and ranging – or LiDAR.

“LiDAR is like radar, but with light,” Davis said. “It gives you information about what’s around the sensor.”

Event attendees gather around a sedan outfitted with a spinning LiDAR sensor. (Photo by Micheal Foley, MnDOT)
Event attendees gather around a sedan outfitted with a spinning LiDAR sensor. (Photo by Micheal Foley, MnDOT)

Davis and his fellow researchers have outfitted a sedan with special LiDAR equipment and other technology that is capable of capturing a 360-degree, 3-D view of a scene in real time.

“We use the car as a test bed,” Davis said. “We have a lot of different types of sensors on the car that we use for the different projects that we’re working on. Right now we have a LiDAR sensor on top. Sometimes we have a high-accuracy GPS receiver in there. We have a cellular modem. We have a handful of inertial sensors. So it’s a lot of different stuff that we use to cater to the application.”

For his presentation, Davis showed the attendees some of the data his team had already collected.

Davis presents data that shows the LiDAR-equipped sedan moving along a roadway. (Photo by Micheal Foley, MnDOT)
Davis presents data that shows the LiDAR-equipped sedan moving along a roadway. (Photo by Micheal Foley, MnDOT)

“We showed a handful of pre-collected data at a handful of intersections around Rochester and Minneapolis,” Davis said. “What it shows is the point cloud collected by the sensor – just the raw point cloud with no post-processing done. In that information you can see people moving through it, cars moving through it, buses and light rail trains.”

Event attendees move around the sedan to see how the LiDAR sensor views them. (Photo by Micheal Foley, MnDOT)
Event attendees move around the sedan to see how the LiDAR sensor views them. (Photo by Micheal Foley, MnDOT)

After the presentation, Davis led the group to the parking lot for a close-up look at the technology and how it collects data and displays that data in real time. Le Sueur County GIS manager Justin Lutterman was among those who could envision possible applications for LiDAR.

“It’ll be interesting to see where this can go,” Lutterman said. “I’m sure the private industry will take off with this and emergency management, or the sheriffs and ambulances, would appreciate this kind of technology on their vehicles for a situation they might have to recreate. Roads and traffic designers  would be able to monitor their resources, pavements, traffic counts and things like that.”

Over the coming months, researchers will gather more data to develop a workshop for county personnel interested in learning more about LiDAR and how it can be applied in their transportation systems.

“The next steps for this project are to collect some data with the car at intersections. Then we can use that information to fine tune our algorithms,” Davis said. “What the algorithms are going to do is take that raw data and give us useful information, like the number of cars, or the time a car passes through an intersection. That all feeds into the workshop we’re developing. The workshop is going to be for county GIS workers, traffic engineers and county engineers who are interested in learning about these technologies.”

Environment, Research

Salt-tolerant sod and seed mixes bring greener roadsides to Minnesota

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For Minnesota’s roadside grasses, life isn’t easy. To survive, grass must be able to withstand extreme stresses including drought, heat, disease, soil compaction, poor quality soils, and high levels of road salt. Ideally, it could survive all that while still looking lush and green.

“Many roadsides, especially in metropolitan areas, need to look good,” says Eric Watkins, associate professor in the Department of Horticultural Science. “In addition to aesthetics, quality roadside vegetation is needed to prevent erosion and maintain water quality from roadside runoff.”

In 2010, MnDOT noticed a number of its new sod and seed plantings were failing and asked U of M experts to take a look at its specification. “We saw the problem immediately,” Watkins says. “The specification was for a mix with a lot of Kentucky bluegrass, which needs a great deal of care and watering. There was clearly an opportunity for improvement.”

During the next several years, Watkins’ team, led by former graduate student Josh Friell, worked to identify the best seed and sod for use along Minnesota’s roadsides in research sponsored by the Minnesota Local Road Research Board and MnDOT. Findings are now available in a final report.

The study was completed in several stages. First, many different types of cool-season grasses were planted in the fall and assessed the following spring to determine their ability to establish and survive on roadsides in Minnesota. Next, researchers looked at the salt tolerance of those grasses.

Eric Watkins (third from left) leads a greenhouse tour of grass mixtures.
Eric Watkins (third from left) leads a greenhouse tour of grass mixtures.

“In cold-weather climates like Minnesota’s, salt tolerance is required because of the application of deicing salts in the winter,” Watkins explains. “To determine if a grass species could stand up to this stress, we applied different levels of salt solution to the different grass species in a greenhouse. We identified several types of fescue grass as the most salt tolerant.”

Based on the results of the first two stages, researchers developed and tested 50 different grass mixtures along Minnesota’s roadsides and evaluated the survival and performance of those plantings for two years. In addition, each mixture was planted under a movable rain-out shelter to determine drought tolerance. This phase of the study resulted in the identification of a mix of three types of fescue for planting on roadsides in Minnesota.

Finally, researchers needed to find out if the new grass mixture would work as sod (sod growers need to be able to harvest it properly from their sod fields). “Most sod currently grown in Minnesota is Kentucky bluegrass, which isn’t the best for winter survival when salt stress is a problem,” says Watkins. “We grew 51 different grass mixtures as sod for 22 months and found that contrary to popular belief, fine fescue mixtures produced sod of acceptable strength for harvest.”

MnDOT has applied the research to standard specifications for construction activities for salt-tolerant sod products, salt/shade/drought-tolerant turf seed mixtures, and a third-party certification program for ensuring performance standards are met based on past and current research results, says Dwayne Stenlund, MnDOT erosion control engineering specialist. Researchers are also working with the state’s sod growers to produce sod grown from the new seed blends.

Moving forward, the researchers plan to continue their work to improve Minnesota’s roadside grass plantings. “The reality is that the success of sod or seed plantings depends on a number of factors, including time of year, amount of water, soil preparation, temperature, and sod harvest depth,” Watkins says. “In our next project, beginning this spring, we will identify the most important factors for the success of roadside plantings and sod cultivation, and then help MnDOT update the specifications for managing new installations.”

Policy and Planning, Research

Travel behavior study shows drivers are spending less time traveling

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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.

Research

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

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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!

Research, Traffic and Safety

New permitted left-turn model helps improve intersection safety

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In recent years, the transportation community has introduced significant changes to improve left-turn safety at signalized intersections—and for good reason. Nationally, intersection crashes represent one-fifth of all fatal crashes, and most of these are crashes involving left turns.

In response to this serious safety problem, the FHWA has adopted a new national standard for permissive left turns: the flashing yellow arrow. This signal warns drivers that they should proceed with a left turn only after yielding to any oncoming traffic or pedestrians. Flashing yellow arrow signals can help prevent crashes, move more traffic through an intersection, and provide additional traffic management flexibility.

Many transportation agencies, including MnDOT, are interested in using the new flashing yellow arrow signals to accommodate within-day changes: protected left turns (signaled by a green arrow) could be used when needed to lower crash risk, while permitted left turns (signaled by a flashing yellow arrow) could be used to reduce delay when crash risk is low.

“Of course, this requires being able to predict how the risk of left-turn crashes changes as intersection and traffic characteristics change within the course of a day,” says Gary Davis, a professor of civil, environmental, and geo- engineering at the University of Minnesota.

To help engineers make more informed decisions about when to use flashing yellow arrows, Davis is leading the development of a model that could help predict the probability of left-turn crash risk at a given intersection at different times of day. This model—which will ultimately be available as a set of spreadsheet tools—will help traffic engineers determine when the crash risk is sufficiently low to allow for the safe use of flashing yellow arrows. The project is sponsored by MnDOT and the Minnesota Local Road Research Board.

To develop the statistical model, the researchers needed to determine how the risk for left-turn crashes varies depending on time of day, traffic flow conditions, and intersection features (such as number of opposing lanes, number of left-turn lanes, and median size). The process included developing a database containing left-turn crash information, intersection features, and traffic volumes, as well as developing a set of 24-hour traffic pattern estimates to help fill gaps where hourly traffic volume counts were not available. The resulting statistical model uses this information to determine relative crash risk for every hour of the day at a given type of intersection.

Currently, Davis and his team are using the model to develop a spreadsheet tool that will allow traffic engineers to choose their type of intersection and enter the available turning movement count. The tool will then generate a specialized graph for that intersection showing the relative crash risk by time of day. Any time the crash risk is at or below the level identified as acceptable, engineers can consider using flashing yellow arrows.

“By simulating how crash risk changes as traffic conditions change, this model could help identify conditions when permitted left-turn treatments would be a good choice and what times of day a protected left turn might be a better option,” Davis says.

Moving forward, Davis is leading an additional project related to the use of flashing yellow arrows, funded by the Roadway Safety Institute. The project will first review video data of drivers making permitted left turns to characterize left-turn gap acceptance and turning trajectories. Then, Davis will incorporate the findings into the existing statistical model. To further improve the model’s accuracy, the study will compare the crashes described by the simulation model with reconstructed real-world left-turn crashes.

Research

MnDOT, LRRB Pick New Research Projects with Financials in Mind

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Minnesota’s transportation research governing boards put a new emphasis on financial benefits when selecting next year’s round of transportation research projects.

MnDOT’s Transportation Research Innovation Group (TRIG) and the Local Road Research Board announced their Fiscal Year 2016 funding awards this week after hearing proposals from researchers in several states. They selected 20 research proposals hall-marked by novel approaches to improving the environment, increasing transportation safety, improving construction methods and boosting the bottom line.

“We asked the principal investigator to present the safety and financial benefits up front, and how they can be implemented to improve the transportation system and economic viability of Minnesota,” said MnDOT Research Management Engineer Hafiz Munir. “We’re making a point early in the process to identify those potential benefits, quantify them and document them in our tracking system.”

Researchers will test new technology that could make crack-free pavements; find better, faster and less expensive ways to reclaim roads; and even explore how to use waste material from road construction projects as part of the landscaping to absorb water runoff.

Links are provided below to brief descriptions of each of the projects:

Bridges and Structures

Environment

Maintenance

Materials and Construction

Multimodal

Policy and Planning

Traffic and Safety

Research, Traffic and Safety

Teen Driver Support System helps reduce risky driving behavior

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Although teen drivers make up a small percentage of the U.S. driving population, they are at an especially high risk of being involved in a crash. In fact, drivers between ages 16 and 19 have higher average annual crash rates than any other age group.

To help teen drivers stay safe on the road, researchers at the U of M’s HumanFIRST Laboratory have been working for nearly 10 years on the development of the Teen Driver Support System (TDSS). The smartphone-based application provides real-time, in-vehicle feedback to teens about their risky behaviors—and reports those behaviors to parents via text message if teens don’t heed the system’s warnings.

TDSS provides alerts about speed limits, upcoming curves, stop sign violations, excessive maneuvers, and seat belt use. It also prevents teens from using their phones to text or call (except 911) while driving.

The research team recently completed a 12-month field operational test of the system with funding from MnDOT. The test involved 300 newly licensed teens from 18 communities in Minnesota.

To measure the effectiveness of the TDSS on driving behavior, the teens were divided into three groups: a control group in which driving behavior was monitored but no feedback was given, a group in which the TDSS provided only in-vehicle feedback to teens, and a group with both in-vehicle and parent feedback from the TDSS.

Preliminary results show that teens in the TDSS groups engaged in less risky behavior, especially the group that included parent feedback. These teens were less likely to speed or to engage in aggressive driving.

Although these results demonstrate that the TDSS can be effective in reducing risky driving behavior in teens, Janet Creaser, HumanFIRST research fellow and a lead researcher on the project, stresses that technology is not a substitute for parent interaction.

“The whole goal of our system is to get parents talking to their teens about safe driving.” Creaser says. “And maybe, if you’re a parent getting 10 text messages a week, you’ll take your teen out and help them learn how to drive a little more safely.”

Read the full article in the November issue of Catalyst.

Policy and Planning, Public Transit, Research

Access Across America: University of Minnesota ranks accessibility to jobs by transit

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New research from the Accessibility Observatory at the University of Minnesota ranks 46 of the 50 largest (by population) metropolitan areas in the United States for accessibility to jobs by transit.

The new rankings, part of the Access Across America study begun last year, focus on accessibility, a measure that examines both land use and transportation systems. Accessibility measures how many destinations, such as jobs, can be reached in a given time.

“This project provides the most detailed evaluation to date of access to jobs by transit,” says Andrew Owen, director of the Observatory. “We directly compare the transit accessibility performance of America’s largest metropolitan areas.”

The findings have a range of uses and implications. State departments of transportation, metropolitan planning organizations, and transit agencies can apply the evaluations to performance goals related to congestion, reliability, and sustainability. In addition, detailed accessibility evaluation can help in selecting between project alternatives and prioritizing investments.

“It can help reveal how the costs and benefits of transportation investments are distributed,” Owen says.

Top 10 metro areas: job accessibility by transit (January 2014)

  1. New York
  2. San Francisco
  3. Los Angeles
  4. Washington
  5. Chicago
  6. Boston
  7. Philadelphia
  8. Seattle
  9. Denver
  10. San Jose

The report—Access Across America: Transit 2014—presents detailed accessibility values for each of the 46 metropolitan areas, as well as detailed block-level color maps that illustrate the spatial patterns of accessibility within each area. In addition, time-lapse map videos for each area are forthcoming and new analysis of the data from the accessibility to jobs by transit rankings will be published periodically. Upcoming reports in the Access Across America series will explore more detailed aspects of transit accessibility to jobs, including accessibility to jobs of different wage levels and a comparison with accessibility by car.

In the study, rankings were determined by a weighted average of accessibility, giving a higher weight to closer jobs. Jobs reachable within 10 minutes were weighted most heavily; jobs were given decreasing weight as travel time increases up to 60 minutes. Travel times were calculated using full transit schedules for the 7:00 to 9:00 a.m. period. The calculations include all components of a transit journey, including “last mile” access and egress walking segments and transfers.

“Accessibility is the single most important measure in explaining the effectiveness of the urban transportation system,” says David Levinson, University of Minnesota civil engineering professor and principal investigator on the project.

According to Owen, accessibility can be measured for various transportation modes, to different types of destinations, and at different times of day. “There are a variety of ways to define accessibility,” Owen explains, “but the number of destinations reachable within a given travel time is the most directly comparable across cities.”

The research is sponsored by the Center for Transportation Studies at the University of Minnesota. Accessibility Observatory reports, including the analysis of job accessibility by auto published last year and interactive maps, are available on the Access Across America: Transit 2014 web page.

Materials and Construction, Research

Program offers funding for “homegrown” road maintenance ideas

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Attention Minnesota road maintenance staff:

Have you ever dreamed that all of your tinkering, fussing, and fiddling in the shop and on the road could help improve every road in Minnesota? Do you need funding to improve your sign maintenance and installation process? Or maybe you’ve come up with an idea for a new tool for controlling roadside vegetation or a design for a more effective work-zone safety product. Whatever it is, the Local Operational Research Assistance (OPERA) Program wants to hear about it.

Funding for 2015 OPERA projects is now available, and it’s easy to submit a proposal. Simply fill out the brief proposal application (50 KB DOC) and submit it via e-mail to Mindy Carlson at Minnesota LTAP. There isn’t a deadline to submit your proposal, but FY15 funds are limited and they often go quickly.

The maximum funding per project is $10,000, and local agencies are welcome to submit more than one proposal.

Project Guidelines

Your proposed research project should focus on the timely development of relevant ideas or methods that improve transportation or maintenance operations. Our goal is to collect and disseminate homegrown, innovative solutions to the everyday challenges our transportation workforce faces on the job. Counties, cities, and townships, this is your opportunity to encourage your maintenance staff to become actively involved in researching and testing their ideas.

To see what other local agencies have done with OPERA funding, check out our fact sheets and annual reports, or watch these videos highlighting previous OPERA projects:

Program Sponsors

The Local OPERA Program is funded by the Minnesota Local Road Research Board and administered by the Minnesota Local Technical Assistance Program.

Research, Traffic and Safety

MnPASS: Two systems, both work

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I-35W’s MnPASS lane, where vehicles can frequently enter and exit the high-occupancy toll lane, is just as safe as the MnPASS lane on I-394, where motorists only have a few shots to enter the system, a new study finds.

Researchers at the Minnesota Traffic Observatory undertook the MnDOT-funded study because of objections to open systems like the one on 35W.

“The federal government has very strong arguments against the open system. They’re saying it’s going to be dangerous – cause more disruption and more congestion,” said John Hourdos, director of the Minnesota Traffic Observatory. “We found that both roadways are working very well today because they were designed appropriately for their location.”

The definition of an open system is one that has more opportunity for access than restriction. On 35W, a dotted white lane means vehicles can enter the toll lane at will, and a solid line bars access.

Vehicles must have two occupants on-board or an electronic pay card to use the express lanes during rush hour.

MnPASS on Highway 35W.

The reason I-35W allows vehicles to enter MnPASS more frequently than I-394 is because there are more ramps where new vehicles are entering the freeway and might want to get on MnPASS.

Researchers studied whether accidents are more likely to occur by studying the number of accident-inducing vehicle movements along the 35W corridor. They found that areas where accidents are mostly likely to occur are also where the lane would have to allow access anyway under a closed system like 394.

The study also looked at mobility, determining that MnPASS users have just as good free-flowing traffic under the open system.

Helpful tools

Researchers also created design tools that engineers can use to determine where access points should be on MnPASS lanes.

Until now, engineers have relied on rule of thumb. For example, the general guidance for allowing access on a closed system was 500 feet for every lane between the entrance ramp and the HOT.

The tools can be used to automatically determine how fluctuations in the MnPASS fee will affect congestion within the lane.

The fee to use MnPASS depends on the time of day.

As the express lane become more congested, the fee to use it increases. This slows the number of cars entering the lane, increasing the speed of the vehicles already in the lane.

“We ran the tool on three locations on 35W and found that, for example, on Cliff Road, you can increase the traffic by 75 percent and still be okay,” Hourdos said. “You have more leeway there than north of the crossroads of Highway 62 and 35W, for instance.”

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