Introducing new CTS blog: Conversations

CTS Conversations blog iconCTS is pleased to announce a new blog—CTS Conversations—that will highlight the full spectrum of transportation research, education, and outreach at the University. Supplementing the Catalyst newsletter and the Crossroads blog, the Conversations blog will share timely updates on research publications, events, and training from CTS and its programs.

Also, the blog will feature topical questions to spark conversation and interaction with our readers. Check out the current question and join the conversation!

CTS fall research seminars begin September 26

This fall, CTS will offer five research seminars on transportation topics ranging from resilient communities to asphalt at low temperatures.

Seminars will be held every Thursday from September 26 through October 31 (except Oct. 17) on the U of M campus in Minneapolis. You can either attend in person or watch the live webcast of each seminar. Additional information is available on the CTS website.

Seminar schedule:

Using an infrared camera to inspect a bridge deck

Over the last several years, MnDOT has been participating in a national pooled-fund study on using infrared cameras to spot subsurface damage on bridge decks. These damaged areas just below the deck surface are called “delaminations,” and they’re what causes potholes and cracks on the surface. Detecting them is a key part of what MnDOT bridge inspectors do, and it’s huge challenge.

Currently, one of the primary methods of locating delaminations is “chain-dragging” — literally, dragging chains across the surface of a bridge deck. Using this method, inspectors can listen for evidence of hollowed-out areas beneath the surface, which produce a different sound than solid areas. While it works, this practice forces bridge crews to close down lanes and work near moving traffic. These issues have led Minnesota and other states to look for alternatives, and infrared or “thermographic” imaging is one of the top contenders.

In the video above, MnDOT bridge inspector Eric Evens demonstrates how to inspect a bridge deck using an infrared camera (specifically, a FLIR T620 — the model selected for the study). The delaminated areas appear as white or “hot” spots in the image. Evens does a nice job of explaining some of the benefits and potential uses of the camera, including minimizing traffic delays. He also demonstrates the camera’s ability to simultaneously capture photos and infrared images, which could be useful for cataloging the conditions of bridge decks and programming schedules for repairs.

However, as Evens pointed out during the filming, there are both pros and cons to using infrared thermography. One downside is it’s really only effective as the bridge deck warms up in the morning. Another is that it takes some practice to be able to identify which of the “hot spots” are actual delaminations and which are merely dirt or debris on the deck surface, or some other kind of false positive.

Introducing ‘Accelerator,’ a MnDOT research newsletter

Accelerator cover - September 2013

MnDOT Research Services is excited to announce the launch of Accelerator, our new research newsletter.

The bimonthly publication will focus on bringing readers the latest news from MnDOT’s research program. Each issue will highlight recent transportation research results, along with photos, feature stories and a calendar of upcoming events.

Accelerator is geared specifically toward transportation practitioners. It features short summaries of research projects, with links and other resources to help professionals learn more about areas in which they have a particular interest. The ultimate goal is to help bridge the gap between research and implementation by transferring knowledge to those who can put it to work in the field.

Much like Catalyst, the excellent newsletter produced by CTS, Accelerator will be available both in print and online editions. The first issue is scheduled to be released Tuesday, Sept. 3. To subscribe or to learn more, visit our website.

U of M Research: Spurring private-sector development along transit corridors

developmentA new research study is recommending ways to make it easier for developers and employers to select sites that encourage living-wage jobs and mixed-income housing near transit.

A key finding of the study, which was based on interviews with developers and business leaders, revealed a pent-up demand for transit access in the Twin Cities metropolitan region.

A team led by University of Minnesota researchers Yingling Fan and Andrew Guthrie found that providing a great work location is critical for employers in recruiting highly skilled young professionals who are likely to desire—or demand—urban living and access to transit.

They also found that multifamily residential developers, redevelopment specialists, and large corporate office tenants have a strong interest in transit-accessible sites, but regulatory barriers, cost issues, and uncertainty surrounding future development of transit often discourage both developers and businesses from selecting such sites.

More details about the study and key recommendations

New Complete Streets materials highlight best practices

Complete Streets scene
Photo courtesy Carissa Schively Slotterback

A new study from researchers at the U of M’s Humphrey School of Public Affairs aims to help Minnesota practitioners get Complete Streets projects on the ground.

“The goal was to look at what it takes to move a community from Complete Streets concept to Complete Streets project,” says Carissa Schively Slotterback, one of the project’s lead investigators.

As part of the study, Slotterback teamed with her Humphrey School colleague Cindy Zerger to investigate what’s working well in a variety of Complete Streets implementation efforts across the country. The study was sponsored by MnDOT and the Minnesota Local Road Research Board.

Slotterback and Zerger investigated six best practices areas related to Complete Streets: framing and positioning, institutionalizing, analysis and evaluation, project delivery and construction, promotion and education, and funding. Project findings stressed the importance of project context, the need for institutional and cultural changes, and the benefits of engaging advocates and project champions.

Based on the findings, Slotterback and Zerger are creating 11 case studies and a guidebook to help practitioners apply best practices and lessons learned from other communities to their own projects. The materials are set for completion this fall.

To learn more, read an article about the project in the August issue of CTS Catalyst.

Previewing MnDOT’s next round of research projects

MnDOT Research Services recently released its 2013 request for proposals. If you have any kind of direct interest in transportation research in Minnesota, chances are you might have known that already. But those with more of a general curiosity might be interested to see the list of research need statements from the RFP, as they provide a nice preview of the next round of potential MnDOT research projects.

As you can see, some are of a highly technical nature. (It’s safe to say that a study on “PCC Pavement Thickness Variation Versus Observed Pavement Distress” would be of interest mainly to engineers.) Others, however, like “The Economic Impact of Bicycling in Minnesota,” might have a broader appeal. In any case, it’s a fascinating glimpse at the myriad of issues that MnDOT is attempting to address through research and innovation.

Here’s the list of research need statements from the 2013 RFP, broken down by category:

Environment

Maintenance

Materials and Construction

Multimodal

Policy and Planning

Traffic and Safety

What happens when you incentivize transit use during construction projects

In 2010, MnDOT began a three-year long, $67 million repair and upgrade project on I-35 in Duluth. Dubbed the “Mega Project,” it created a serious disruption for Duluth-area commuters. To help mitigate the impact, the Duluth Transit Authority stepped up its bus services, offering free rides in newly established bus-only express lanes as well as access to new park-and-ride lots and various other enticements. Perhaps not surprisingly, many area residents took advantage of their new transit options to avoid construction-related travel delays. But what’s really interesting is what happened after the construction ended.

As described in a recently published MnDOT/University of Minnesota study, commuters who started taking the bus to avoid traffic caused by the construction ended up continuing to ride the bus even after the construction ended. Researchers surveyed riders during and after the 2010 and 2011 construction seasons and found that, even after bus fares went back to normal levels, only 15 percent of the new bus users switched back to driving. Researchers concluded that once riders developed a habit of using transit, the habit tended to stick.

The report author sums up the phenomenon quite nicely in her executive summary:

Human beings are creatures of habit. Most of us travel the same route every day to the same destination. Sometimes, however, something comes along to push us to examine our habits and possibly change them. A major highway construction project can be such an event. (…) This provides a very good opportunity to examine our travel patterns and possibly change our habitual modes.

Of course, this change didn’t just happen on its own. As the technical summary notes, the DTA marketed its services aggressively during this period. (The above photo is just one example.) The study also noted that the elimination of expanded bus services in the winter had a negative impact on ridership.

Read more:

Geotextile research at MnROAD

Geotextiles are synthetic polymer materials used to improve the performance of roadways. As discussed in this 2011 technical summary, geotextiles facilitate filtration and water drainage, improve the integrity and functioning of base materials, and provide a stable construction platform over soft or wet soils. These improvements can benefit both the cost-efficiency and longevity of pavements.

Geosynthetic materials have been used throughout Minnesota, and can be found in both reconstructed and new roadway projects. The use of geotextiles as a separator layer under concrete overlays, however, has had limited documentation in Minnesota and other cold weather climates. MnROAD‘s recent dedication of several test cells to this purpose will determine the performance of this application of geotextiles, with the goal of improving its applications on other Minnesota roadways.

The new test sections, designated as Cells 140 and 240, consist of a very thin, 3-inch concrete overlay over an existing 7-inch concrete pavement constructed 20 years ago. Some unique features of the design include the use of a fiber-reinforced concrete mix, two different thicknesses of the nonwoven geotextile, and the use of a special type of glue, rather than nails, to fasten it to the existing concrete before paving.

The fabric and fiber used in the concrete mix were supplied through a public-private partnership with Propex Geotextile Systems. The results of this study, along with other unbonded overlays constructed at MnROAD and around the country, will be incorporated into a new national pooled fund project — TPF 5-(269) — led by MnDOT. This project will develop an improved mechanistic design procedure for unbonded overlays.

A second application being demonstrated at MnROAD is the use of a geosynthetic drainage system under several dowel bar baskets in new concrete pavement test section. Minnesota has historically used a dense-graded base layer under concrete pavements to provide a stable foundation and construction platform. However, this material drains very slowly, and traps moisture within the joints, leading eventually to significant distress (See Effect of Drainage on the Performance of Concrete Pavement Joints in Minnesota.) This application will compare the use of the geotextile drainage material placed under both sealed and unsealed joints, as well as a control joint without the drainage material.

Best practices for trail crossings – webinar and draft report

Last week, MnDOT Research Services hosted a workshop on a forthcoming report, “Decision Tree for Identifying Alternative Trail Crossing Treatments.” It was broadcast as a webinar, the recording of which is now available online via Adobe Connect:

http://mndot.adobeconnect.com/p8hlfripuwe/

The final report is coming soon, but in the meantime you can see the draft version on our website (link), along with case studies and other related documents.

Minnesota's transportation research blog