Data was primarily collected via cameras at the I-94 Commons Third Avenue Field Lab station, overlooking an area with a particularly high crash rate.

What those signs over the freeway are actually telling you

Two years ago, MnDOT installed a series of electronic speed limit advisory signs over Interstate 94 between Minneapolis and St. Paul. The Variable Speed Limit (VSL) system is designed to reduce congestion and help prevent crashes by recommending lower speed limits to motorists during periods of high traffic.

The new technology has worked in other places, including China and Germany. In Minnesota, a similar VSL system on I-35W reportedly had moderate benefits in reducing the total amount of congestion during the morning commute south of Minneapolis.

Although the verdict on I-94 congestion is still pending,  a newly released study has found that the new system has not made a measurable impact so far on crashes in an accident-prone stretch of freeway in downtown Minneapolis. Why not?

University of Minnesota researcher John Hourdos has a few theories.

One is a simple time  lag in the congestion reporting system. Another is a requirement that all lanes display the same speed limit, which he said causes confusion when only one lane is actually congested. The complexity of the I-94 commons also appears to be beyond what the VSL system was designed to do. And according to Hourdos, one of the most significant problems is the driving public simply doesn’t understand what the signs are telling them.

“People do not know what the system really does,” Hourdos said. “There hasn’t been much education on it other than a couple of news articles over the years. And when they try to decipher it on their own they get even more confused.”

The I-94 Commons area has a major bottleneck where the I-35W northbound ramp merges with I-94 westbound (between Cedar Avenue and 11th Avenue). Vertical red lines indicate locations of gantries that display variable speed limit advisories.
The I-94 Commons area has a major bottleneck where the I-35W northbound ramp merges with I-94 westbound (between Cedar Avenue and 11th Avenue). Vertical red lines indicate locations of gantries that display variable speed limit advisories.

The advisory speed limits are posted in response to varying traffic conditions. As vehicles approach the commons area, the system measures speeds at the bottlenecks. If the traffic slows, the system transmits a reduced advisory speed to drivers approximately 1.5 miles upstream from the location of the slow-down.

Hourdos said many motorists mistakenly believe the speed displayed on the signs is either a reflection of the speed on the current stretch of highway or an indication of the speeds on the highway ahead, rather than a suggested speed for them to follow.

The requirement to display the same speed limit on all signs also compounds the problem, Hourdos said, because when drivers see that the slowdown is only occurring in certain lanes they tend to ignore the signs altogether.

“In the lane that is congested, the real speeds drop much faster than what the VSL system can respond to, reducing the functionality of the system to the eyes of the drivers,” Hourdos said, “while on the fast-moving lanes, it seems the system has no purpose at all.”

From downtown Minneapolis rooftops, traffic monitoring cameras detect shockwaves on Interstate 94.
Data was primarily collected via cameras at the I-94 Commons’ Third Avenue Field station, overlooking an area with a particularly high crash rate.

So is the I-94 VSL system useless? Not necessarily. For one, the new study didn’t measure the system’s impact on congestion — only its ability to reduce crashes on a small portion of I-94. Moreover, the area in question, the I-94 Commons, is fairly unique, having two major bottlenecks, the highest crash rate in the state (nearly one every other day), and five hours of congestion during the afternoon rush hour alone.

“The VSL system was designed for implementation on any freeway and may not have been well-suited for the I-94 Commons area, which is a very complex corridor with high volume weaves and significant shockwave activity,” said MnDOT Freeway Operations Engineer Brian Kary.

Generally speaking, the VSL system was designed to identify slow traffic ahead of where free-flowing traffic is approaching slow or stopped traffic.

“The crash problems within the commons are caused by speed differentials between lanes and shockwave activity within the congestion,” Hourdos said. “The current VSL system was not developed to handle these types of conditions.”

MnDOT and the researchers aren’t giving up, either. A new project is starting later this year to develop and deploy a queue warning system specifically for this high-crash rate location.

Further resources

Investigation of the Impact of the I-94 ATM System on the Safety of the I-94 Commons High Crash Area (PDF), May 2014

Improving Traffic Management on Minnesota Freeways (PDF), May 2012

Study of the Impacts of Implements of Husbandry on Bridges

Study to develop bridge load limits for tractors

Minnesota farm equipment is getting larger and heavier, causing strain on rural bridges. However, there are no  nationally recognized specifications for what size and weight of tractors can safely travel over them.

Currently, bridge load limits are based off semi-trucks, not farm machinery, which have much different axle configurations and wheel dimensions.

“Their geometry is atypical; their length, widths are different; they have different suspension characteristics,” explains Brent Phares, director of the Bridge Engineering Center at Iowa State University.

A new pooled fund study led by the state of Iowa is attempting to determine how much stress heavy farm vehicles put on bridges. This data will be used by local agencies to develop weight restrictions specifically for farm equipment.

“It will help limit the confusion of current load posting signs for farmers,” said MnDOT bridge load rating engineer Moises Dimaculangan.

Wisconsin, Minnesota, Nebraska, Oklahoma, Illinois, Kansas and the United States Department of Agriculture are also participating in the study, which is examining three types of local bridge superstructures: those with steel girders and concrete decks; bridges with steel girders and timber decks; and timber bridges with timber decks.

Through physical testing and modeling, the study will determine how different types of farm machinery distribute their loads on the bridge superstructure.

About a half-dozen farm vehicles were tested on 20 different bridges which were representative of those tending to be the most problematic for farm equipment traffic on secondary road systems, Phares said.

Instrumentation measured the response of the structures to the vehicles. This data was then used as a baseline to calibrate analytical models, which could be applied to 250 different bridges and 121 different farm vehicles.

Researchers will develop a generic tractor profile, which represents the worst-case scenario, for use in determining load limits. With the information developed, signs might be able to be added to the bridges, which show a tractor and the weight limit.Collapsed bridge

“I get a number of pictures emailed to me of bridges that have failed with a tractor implement of husbandry on top,” Phares said. “That’s the problem that people are looking to avoid; the goal isn’t to restrict the size of farm vehicles, but to develop better tools for engineers to make sound and solid analyses for the bridges, so they can provide that information to the people who need to have it.”

Phares said a couple previous studies have also looked at farm machinery weight restrictions. One study, from around 2004, took a high level look at the impact of farm vehicles on bridges. A more recent pooled fund study analyzed the impact of machinery on pavements.

Related resources

Research in Progress: Study of the Impacts of Implements of Husbandry on Bridges

The Effects of Implements of Husbandry “Farm Equipment” on Pavement Performance

seatbelt

Primary seat belt law continues to save lives, money

Minnesota’s primary seat belt law continues to save lives and reduce serious injuries more than four years after being passed, according to a study by researchers at the U of M’s Humphrey School of Public Affairs.

The study examined Minnesota crash data collected from June 2009 (when the law was implemented) through June 2013 and compared it to expected data based on crash trends over time. Findings indicate that there were at least 132 fewer deaths, 434 fewer severe injuries, and 1,270 fewer moderate injuries than expected during this time.

According to the researchers, the safety benefits of the law translate into a savings of at least $67 million in avoided hospital charges, including nearly $16 million in taxpayer dollars that would have paid for Medicare and Medicaid charges.

The study was sponsored by the Minnesota Department of Public Safety and led by Humphrey School research fellow Frank Douma and Nebiyou Tilahun, a U of M graduate now on the faculty at the University of Illinois-Chicago.

The researchers also examined seat belt use data and survey results that measured support for the law. Findings show that support increased from 62 percent just before the law was passed to more than 70 percent in 2013, while the percentage of Minnesotans buckling up was at an all-time high of nearly 95 percent in 2013. This shows that some people are wearing their seat belts even though they don’t support the law.

When this increased seat belt use is combined with the reduction in fatalities and injuries, it further demonstrates that people are surviving—and even walking away from—crashes that may have had different results if the primary seat belt law had not been in effect.

Read the full article in the June issue of CTS Catalyst.

MnRoad tour

Peer Exchange: Pavement researchers face similar issues, financial pressures

Soaring construction costs and a rapidly aging infrastructure will require states to revolutionize how they maintain their roadways — but without each other’s help, they won’t be successful.

That was a key message from pavement researchers last week at a MnDOT-hosted peer exchange event, where pavement experts from around North America shared their ideas and research experiences.

“You’ve got to partner with other states, the FHWA and industry,” said Research Engineer Steve Bower of the Michigan Department of Transportation. “We can’t go it alone anymore.”

Researchers at the event reviewed recent pooled-fund studies conducted at MnROAD, MnDOT’s innovative pavement testing center, to review successful implementation strategies, develop common practices to calculate benefits and help prioritize research topics for MnROAD’s  core 2016 research and reconstruction.

The pavement engineers gathered for the event face similar problems in their home states, as demonstrated by the seven pooled fund projects that were discussed. These included developing a better understanding of pavement damage caused by oversized farm equipment, knowing when to chip seal a roadway, developing a test to predict asphalt cracking , creating a national design method for concrete overlays of asphalt roadways and improvements in diamond grinding of concrete pavements.

MnROAD leading the way

State research departments often lack the time or resources to focus on innovations that could reduce future maintenance costs. If not for Minnesota leading the effort on many of these topics and providing a top-notch research facility, the peer exchange attendees said much of this research just wouldn’t happen.

“We don’t have a closed-loop facility with all these different test sections that MnROAD has; no one does,” said Larry Wiser of the Federal Highway Administration’s Turner-Fairbank Highway Research Center.

Researchers came from Missouri, Maine, Texas, Illinois, Michigan, California, Ontario, Wisconsin, Indiana and Washington for the three-day workshop.
Researchers came from Missouri, Maine, Texas, Illinois, Michigan, California, Ontario, Wisconsin, Indiana and Washington for the three-day workshop.

WisDOT Chief Materials Management Engineer Steven Krebs said the research done at MNROAD on the impact of modern farm implements on pavement was invaluable in drafting new state legislation. WisDOT was able to quantify the amount of damage done to the pavement and use the data to dispute mistruths and  misinformation. The state is now working with counties on possible remedies and weight-limit enforcement techniques.

Whereas Minnesota has taken the lead on studying such issues, it is now asking fellow states to not only participate in future such studies, but to also partner in the operations at MnROAD.  At the peer exchange, the response to this idea — especially from states closest to Minnesota — was positive, despite everyone’s lean budgets.

Peer exchange participants said more effort and funding is needed to implement research findings, which FHWA officials said costs significantly more than the research itself.

Past research also needs to be more accessible and there should be better sharing of information, particularly online, they said.

“This (peer exchange) gave us ideas to take back. Our research budget is getting tighter. It’s nice to be able to say, ‘You do a part of it and we’ll do a part of it,’ ” said California transportation researcher Joe Holland.

Further Resources

2014 Peer Exchange – Presentations

UAS

Unmanned aircraft systems create buzz of activity, but challenges remain

In late 2013, Amazon.com announced that it plans to someday use unmanned aircraft systems (UASs) to deliver packages. Amazon is not alone in considering these systems—the list of potential uses for this technology is rapidly expanding. Where is this technology headed, and what does it mean for the region, and for transportation?

State and national experts discussed these issues at an April 30 forum hosted by the Airport Technical Assistance Program (AirTAP), a part of CTS.

Often referred to as drones, modern UASs can be used for a broad range of activities, from aerial photography, surveying, precision agriculture, and communications to disaster response, wildlife research, and infrastructure protection.

Potential uses of UASs include precision agriculture.
Potential uses of UASs include precision agriculture.

A hurdle to broader use is the lack of rules and regulations. Last November the Federal Aviation Administration (FAA) released its first annual roadmap outlining policies, regulations, technologies, and procedures needed to safely integrate UASs into U.S. airspace; it plans to issue regulations by 2015.

“The greatest challenge is integrating UASs into the National Airspace System,” said Brigadier General Alan Palmer, director of the Center for UAS Research, Education, and Training at the University of North Dakota. “We want to do this safely, we want to do no harm, and we want to be sure not to violate somebody’s personal space. We do not have any regulations for standards, training, certification, or anything like them. But we will get there.”

Other concerns include privacy issues and the existing aviation/navigation infrastructure, which did not account for a future including UASs when it was built 50 years ago.

To learn more about the forum, read the full article in the June issue of Catalyst. In addition, a proceedings from the event will be available on the AirTAP website this summer.

From left, Dave VanDeusen from MnDOT, LaDonna Rowden from the Illinois Department of Transportation, Magdi Mikhail from the Texas Department of Transportation and Samy Noureldin from the Indiana Department of Transportation. — at Holiday Inn Bloomington I-35W.

MnROAD 2014 Peer Exchange (photo gallery)

MnROAD is hosting pavement researchers from around North America this week to discuss research conducted at its cold weather pavement testing facility in Albertville, Minnesota.

Participants at the three-day conference (June 10 to 12) are reviewing the findings of recent pooled fund studies, sharing their implementation experience and recommending what projects should be picked for the next round of research.

Bob Orthmeyer from the Federal Highway Administration, said MnROAD was the only facility in the country that could supply several test sections needed for a recent study.
Bob Orthmeyer from the Federal Highway Administration said MnROAD is the only facility in the country that could supply several test sections needed for a recent study.
Graig Gilbertson from MnDOT District 8 listens to one of seven presentations Tuesday on the latest research.
Graig Gilbertson from MnDOT District 8 listens to one of seven presentations Tuesday on how agencies have implemented MnROAD’s second phase of research projects.
Stephen Lee shares the Ontario Ministry of Transportation's experiences during a discussion Tuesday on research implementation.
Stephen Lee shares the Ontario Ministry of Transportation’s experiences during a discussion Tuesday on research implementation.
Steve Bower, a Michigan Department of Transportation Research Engineer, visits with MnROAD researcher Bernard Izevbakhai, right, and others during a break.
Steve Bower, a Michigan Department of Transportation Research Engineer, visits with MnROAD researcher Bernard Izevbakhai, right, and other peers.
Construction engineering professor Joe Mahoney, from the University of Washington, leads a group discussion on improving research efforts at the close of the session Tuesday.
Construction engineering professor Joe Mahoney, from the University of Washington, leads a group discussion on improving research efforts at the close of the session Tuesday.
From left, Dave VanDeusen from MnDOT, LaDonna Rowden from the Illinois Department of Transportation, Magdi Mikhail from the Texas Department of Transportation and Samy Noureldin from the Indiana Department of Transportation. — at Holiday Inn Bloomington I-35W.
From left, Dave VanDeusen from MnDOT, LaDonna Rowden from the Illinois Department of Transportation, Magdi Mikhail from the Texas Department of Transportation and Samy Noureldin from the Indiana Department of Transportation.
Researchers came from Missouri, Maine, Texas, Illinois, Michigan, California, Ontario, Wisconsin, Indiana and Washington for the three-day workshop.
Researchers came from Missouri, Maine, Texas, Illinois, Michigan, California, Ontario, Wisconsin, Indiana and Washington for the three-day workshop.

 

a rumble strip

Rumble Strips vs. Mumble Strips: Noise Comparison (Video)

We recently blogged about a research project to evaluate a new type of rumble strip that produces significantly less external noise than traditional designs. The above video, shot near Thief River Falls, Minnesota, shows a comparison between traditional rumble strip designs and the newer, “sinusoidal” rumble strips (a.k.a. “mumble strips”).

The life-saving benefits of rumble strips are well-established, but traditional designs produce external noise that residents consider to be a nuisance. The issue has pit safety concerns against quality-of-life concerns in some parts of the state. Researchers are investigating whether sinusoidal rumble strip designs, which are much quieter, are effective enough to combat drowsy or inattentive driving.

The video is not exactly a scientific comparison, but it does give the viewer a good sense of the difference in noise levels produced by the two styles of rumble strips. The results of the actual research project are expected to be available later this year.

Back to gravel? As dollars shrink, counties look for solutions

A large percentage of Minnesota’s local highways were built in the 1950s, the same era that birthed the modern interstate system. But the golden age of highway construction has caught up to counties, who are struggling to maintain and rehabilitate aging road systems with fewer and fewer dollars.

“Our economic resources do not meet the financial investment needed as the bulk of our pavements surfaced in the 1950s reach the end of their useful life all about the same time,” said Freeborn County Engineer Susan Miller.

In rural Otter Tail County alone, the cost of road construction has climbed 10.5 percent per year for the past 10 years.

Meanwhile, there has been only one increase in funding — an 8.5-cent bump in the state gasoline tax “that was eaten up the moment it was enacted,” said County Engineer Rick West.

Otter Tail’s funding gap? An estimated $11 million in year 2011 alone.

With no change in sight, counties across the state are banding together in a research project through the Local Road Research Board to identify ways to reduce the size of their road systems and lower preservation costs.

Forced into a corner

The LRRB launched the study at the behest of counties who were considering turning some paved highways back to gravel just to get by — even though it would probably increase long-term maintenance costs.

In addition to providing expertise on that topic, consultants worked with a group of pilot counties to develop other strategies of stretching county road dollars further. These include: changing maintenance schedules; using different gravel road materials; transferring roads to city or township ownership; adopting different road performance measures; and raising local revenue.

“This project of how five different counties approach funding limitations and how to manage a system with constrained resources is one of the best that I have been a part of through the LRRB,” said Miller, who found the data critical to convincing her county board to pass a wheelage tax.

ottertail2

A new way of thinking

Although the ideas developed through the study aren’t entirely new, for a busy county engineer with few staff, the assistance to implement them has been very valuable.

“We’re practitioners — not researchers,” said Otter Tail’s Rick West. “It’s really forced us to look at our system in its entirety and from a long-range perspective. For us, that’s huge.”

The LRRB selected pilot counties (Dakota, Otter Tail, Freeborn, Stearns and Anoka) that reflect the diversity of the state. After researchers help them implement their chosen strategies, they will hold informational workshops for others throughout the state.

“Other counties with similar roadway preservation issues or management structures can follow these best practices,” said Michael Marti of SRF Consulting Group. “There are a lot of tools out there, there just needs to be more demonstration or training on each of these tools.”

Anoka County, for example, undertook a detailed analysis to determine which roads should become city-owned and which roads the county should assume.

The evaluation system used by Anoka, which examines travel data and other factors, could be adopted by other counties.

Public education

While some ways of changing the system of road maintenance may not be immediately popular, the community will get on board if they understand why, said Otter Tail County Board Chairman Wayne Johnson.

For instance, Otter Tail had to explain why it’s more cost-effective to sealcoat four-year-old roads than reconstruct beat-up, low-volume roads.

“That’s hard to get your arms around when it’s been the other way for 50 to 60 years,” Johnson said.

Community residents did, however, reject one possible strategy discussed at eight public outreach meetings: unpaving roads.

Otter Tail’s entire county road network is paved — a reflection of investments made back in the 1950s that have become somewhat of a community ethic for Ottertail’s 57,000 residents (a population that triples during the summer).

Tools used in the study enable counties to illustrate just how far behind they are in terms of maintenance and prioritize where to make improvements.

“Everyone wants roads to be maintained, but until the road system preservation study, nobody understood the magnitude of the funding gap between where we are and what we need to do to preserve the system,” said Johnson, who recently shared his county’s findings at the National Association of County Engineers conference.

The data is critical for the public to understand why a county might seek a local tax or different method of road maintenance.

“It’s far better to try to tell them what the problem is on the front end, rather than defend the decision on the back end,” Johnson said. “We’re after them to buy into something because it’s their roads and their money.”

Resources
  •  The project findings will be completed later this year and available on the LRRB’s website.

What’s the life of a sign?

Traffic signs provide important information to drivers, and are a critical component of traffic safety. In order to be effective, their visibility and readability must be maintained under both day and night conditions.

Key to signs’ effectiveness is a quality known as retroreflectivity — the ability for signs to bounce light back toward a driver’s eyes, making them appear brighter and easier to read.  Retroreflectivity deteriorates with time, so transportation agencies need to actively maintain their signs.

A research project funded by the Local Road Research Board is developing a guide to help cities and counties better manage their signs, and also to meet a new Federal Highway Administration retroreflectivity management requirement while getting the lowest life-cycle costs.

Cities and counties have until June to establish a sign assessment or management method that will maintain minimum levels of sign retroreflectivity.

“Right now there’s a mixture of different management methods, with very little guidance as to what’s appropriate for your agency based on the signs you have and your labor force and equipment,” said Matt Lebens, a MnDOT research project engineer.

Since 1993, the Manual on Uniform Traffic Control Devices has included guidelines for minimum retroreflectivity of pavement markings and signs. The standards are meant to ensure that drivers, especially the growing population of elderly drivers, are able to detect, comprehend and react to traffic signs. The LRRB project is designed to help fill certain knowledge gaps in this area.

Measuring retroreflectivity

Possible methods for ensuring retroflectivity include night-time inspection; use of a reflectometer; spot-checking a sampling of signs that are the same age; or blanket replacement of signs once they reach a certain age.

Although the retroreflectivity of a sign is  guaranteed by its manufacturer to last a certain number of years, it commonly lasts much longer.

“Currently, we don’t have expected sign life guidance for agencies to use. Through this project, we are establishing a control deck for sign sheeting used in the state, and an expert panel will make recommendations on expected sign life ranges,” Lebens said.

Researchers reviewed retro-reflectivity studies from other states and also measured the retro-reflectivity of signs out in the field across Minnesota using a retroreflectometer. As part of this project, MnDOT is providing training on the retroreflectometer and will also make it available for loan to local municipalities. (Watch a video demonstration.)

At MnDOT’s MnROAD site,  control decks contain dozens of signs. In addition to measuring retroreflectivity, the MnDOT Materials lab is monitoring color fade, which has been a larger issue in Minnesota.

“By getting better data as to the real life in-field life span of the signs, agencies will have a more realistic and better informed value for sign life expectancy, as well as potentially reducing costs,” said MnDOT Senior Engineer Mark Vizecky.

Expected life

There’s been no definitive studies to date as to what the life of a sign is, said lead project investigator Howard Preston of CH2M Hill, but the research so far shows it is in well excess of manufacturer warranties.

Cities and counties will be advised to pick an expected sign life that goes beyond the warranty – and then stay tuned.

“The notion is to watch these signs until they fail,” Preston said. “The sheeting material is better than it used to be. The failure might be 20 or 30 years out.”

There are two basic types of reflective sheeting material: beaded and prismatic.

Although beaded is guaranteed to last 10 years, researchers anticipate a retroreflectivity life of between 12 and 20 years old.

For the prismatic material – which has a 12-year warranty – the life cycle is anticipated to be 20 to 30 years.

“Nobody knows for sure, because nobody has actually followed this material to failure in a controlled condition,” Preston said. “On the road, there are so many variables: vandalism, knock-downs, etc.”

 

A test deck at MnROAD.
Researchers look at the test deck at MnROAD. The study panel includes city and county engineers.
Resources

Final report – Traffic Sign Life Expectancy (PDF, 2 MB, 45pages)

gender

Why do men and women travel differently? Study sheds light on gender differences

Despite their more similar roles at work and home than ever before, U.S. men and women continue to have different travel behavior. Historically, employed men have spent more time traveling to work and less time on household and family support trips than women. While this difference is well-documented, explanations for the difference vary widely: some theories say it’s due to biologically driven differences in gender, while others attribute it to socially constructed gender roles or to gendered structural contexts such as labor market segregation and economic inequality.

While much research has examined these theories, few studies have tested their validity based on evidence—which prompted U of M researchers to examine the theories more deeply. “We believe a greater understanding of the underlying reasons for these enduring travel differences is necessary to effectively address the gender equity issue in transportation policy,” says Yingling Fan, assistant professor in the U’s Humphrey School of Public Affairs.

Researchers set out to test the competing theories by analyzing publicly available data from the American Time Use Survey (ATUS) in various ways across groups of workers with different types of family structures. (ATUS is an ongoing time diary study funded by the U.S. Bureau of Labor Statistics.)

First, they tested the theory that travel behavior differences were based on biologically driven gender differences. “If this theory was true, travel differences between men and women could be applied across all population groups regardless of family structure, but this was not the case,” Fan explains. “We found that single female workers and single male workers exhibit no significant difference in travel behavior.”

Next, the team studied the impact of gendered structural contexts, such as women’s greater presence in pink-collar occupations and significantly lower earnings. The team found moderate support for this theory. “These factors are associated with shorter work travel time among some—but not all—family structures,” Fan says.Shopping

Researchers did find strong support, however, for the theory that socially constructed gender roles explain travel behavior differences. “We discovered that while marriage alone doesn’t differentiate travel behavior between men and women, parenthood does have a significant impact,” Fan says. “Interestingly, we found that even being the sole breadwinner does not insulate mothers from socially constructed gender roles—female breadwinners in married single-worker households with children have shorter work commutes and more household support travel than male breadwinners in the same family structure.”

According to the researchers, these findings have important implications. First, policies to minimize auto travel (for environmental purposes, for example) may be unfair to women who wish to reach more job possibilities through longer commutes. In addition, the findings highlight the importance of incorporating parenthood as a prime variable in understanding the gender and mobility connection.

Finally, this research provides insights on how future growth or decline in specific family structures may shape travel demand. “As childless households continue to grow in relation to households with children, it’s possible that fewer female workers will be confined by short work commutes and may choose to spend more time commuting to more desirable jobs, placing new demands on the transportation system,” Fan says.

The research was funded in part by a Minnesota Population Center Program Development Grant.

Reprinted from the May 2014 issue of CTS Catalyst.

A Minnesota transportation research blog

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