MnDOT tests new technologies to monitor bridge scour

A research implementation project could provide MnDOT with a new set of tools to help combat a major source of bridge failure.

The MnDOT Bridge Office is testing several new methods of monitoring bridge scour — erosion that occurs around bridge piers and abutments during high water-flow events like floods. Acting Waterway Engineer Nicole Danielson-Bartelt said the project’s goal is to be able to monitor scour-critical bridges remotely rather than sending maintenance personnel out on the water during difficult or hazardous conditions.

“There are a number of bridges that are pretty difficult to monitor, especially during high water events,” she said. “Typically, you need to get out on a boat and do either sonar readings or drop weights. It’s dangerous work to be out on the water during those types of events unless you have the right training.”

The project will evaluate several different monitoring technologies, including continuous monitoring equipment like tilt meters and active sonar. The sonar systems, which allows continuous stream bed and water surface elevation data to be transmitted to a website for graphical display, could provide benefits that go beyond monitoring individual bridges.

“The ability to collect continuous, long-term data could help engineers understand short term scour-fill and long term aggradation-degradation cycles,” said Solomon Woldeamlak, a Bridge Office hydraulic engineer. He added that the data can be used to calibrate existing methods of estimating scour at bridges.

Other devices being tested include “float-out” devices, which are buried in the sand around the abutment and send out a signal only if washed to the surface by a scour. Danielson-Bartelt said these non-continuous monitoring devices might be appropriate for bridges where installing permanent sonar is not advisable due to the presence of debris that could damage the equipment.

Monitoring equipment has been installed at two locations: the Highway 43 Winona bridge over the Mississippi River and the Highway 14 Mankato bridge over the Minnesota River. A final report on the project is expected in late 2014/early 2015. You can learn more about some of the products that are being tested on the website of ETI Instrument Systems, Inc., which provided the equipment.

‘Intelligent’ traffic drum could help prevent work-zone tragedies

2012-26 Image
A prototype of the Intelligent Drum Line system.

Work-zone safety is a serious, ongoing challenge for transportation agencies. According to MnDOT, the current three-year average for Minnesota work zones is 1,819 crashes and seven fatalities per year. And that’s not counting near-misses: just talk to anyone who has worked as a flagger, and they will likely have a story about diving into a ditch to avoid being hit by a distracted driver. Consequently, MnDOT is constantly exploring ways to make work zones safer — which brings me to the photo above.

What you’re looking at is no ordinary traffic cone. It’s a prototype of a new warning device called the Intelligent Drum Line system — basically a modified orange traffic drum packed with electronics that can detect speeding drivers and blast them with audiovisual cues to let them know they’re entering the work zone too fast.

Our new technical summary explains the details of the new system, which was developed at the University of Minnesota, with funding and in-kind assistance from MnDOT:

The prototype design uses two modified traffic drums placed 1 to 3 feet from the shoulder of the road and 300 to 400 feet apart. Sensors in the first drum detect vehicles, measure their speed and distance, and communicate this information to the second drum…

When the IDL system detects an oncoming vehicle traveling faster than a threshold speed, the system activates visual warning systems in both drums and initiates a countdown. When the speeding vehicle is approximately 1 second away from the first drum, the system activates an air horn to warn the driver.

As the vehicle passes the first drum, the audible alarm terminates and the system transmits a command to the second drum to start another countdown. When the vehicle is approximately 1 second away from the second drum, the system activates another audible alarm.

Testing of the IDL system at MnROAD has been successful; however, researchers still need to study how drivers react to the system in real-world conditions. Before they can do that, the design will have to be refined so that it can pass Federal Highway Administration crashworthiness tests. On a related note, MnDOT is currently funding a separate University of Minnesota study into which technologies are most effective at capturing drivers’ attention in work zones. The study will include visual and auditory cues similar to the ones used in the IDL prototype.

Learn more:

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:

Minnesota transportation research blog