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.

Are energy-efficient streetlights cost-effective?

In 2010, the City of Minneapolis installed 55 energy-efficient streetlights from nine different manufacturers along 46th Street between 34th and 46th avenues. The project, part of Hennepin County’s Minnehaha-Hiawatha Community Works program, was designed to field test various models of light-emitting diode (LED) and induction lights. Over the course of two years, researchers observed, evaluated and compared the performance of various lighting products, detailing the results in a recently published report available on the MnDOT Research Services website.

In a broad sense, the results of the study would appear to confirm what has become common knowledge regarding energy-efficient technologies: while they cost  more up front, in the long run they have the potential to save money in the form of reduced energy and maintenance costs. The study also demonstrates that  energy-efficient streetlights are capable of producing adequate light output and are well-received by residents.

However, if the big question is whether energy-efficient streetlights can save local governments money, the answer  is somewhat complicated. The study found that both the levels of light ouput and the amount of time it takes to recoup costs varies significantly by product. Page 16 of the report (page 25 of the PDF) features a table comparing various products’ light output and estimated payback time. With one notable exception, the results show that products with the highest light output (i.e. the highest performers and therefore the most desirable) tend to also have the longest payback time. The amount of time it takes to generate a cost savings from energy-efficient streetlights can be as short as 2.6 years or as long as 24 years, depending on the product.

Some other interesting tidbits from the study:

  • Researchers observed operational cost savings of 50-75 percent, depending on the product.
  • Eighty percent of the savings came from reduced maintenance costs, while only 20 percent came from reduced energy costs.
  • In a survey of area residents, 76 percent responded positively to the new, energy-efficient lights.

The study demonstrated that energy-efficient streetlighting is a feasible option for local governments, with the caveat that agencies need to research lighting products thoroughly before making a choice as to which one to use. Ultimately, considering the ever-decreasing cost of LEDs, the use of energy-efficient streetlighting technologies is likely to grow.

Read more:

Ridership and Pedestrian Impacts of Transitways: A Case Study of Hiawatha Light-Rail Transit in Minneapolis

Following up on Nick’s post last week about transportation practitioners’ preferences for short research summaries, the Center for Transportation Studies recently published a two-page research brief highlighting results from a University of Minnesota study that explores the ridership and pedestrian impacts of the Hiawatha Line in the Minneapolis–St. Paul metropolitan region. The study compares the travel behavior of residents in the LRT corridor to those in similar corridors without LRT but with comparable bus service. It investigates the reasons why residents choose to live in the LRT corridor, the associations between transit use and residency in the LRT corridor, and the effects of LRT and the built environment on pedestrian travel.

Findings

mapp

The findings include:
  • Residents who lived in the Hiawatha Corridor when the light-rail transit (LRT) line opened increased their transit use substantially—a clear ridership bonus from LRT.
  • Residents who moved into the corridor after the LRT line opened use transit as often as new residents in similar urban neighborhoods without LRT.
  • When looking for a place to live, good transit service and job accessibility are important factors for both urban and suburban residents—ranked behind only housing affordability and neighborhood safety.
  • Residents choose to live near Hiawatha LRT stations because of their strong preference for transit access and quality.

Recommendations

To encourage transit use among station-area residents, the researchers recommend the following:

  1. Consider development potential when planning LRT routes and design a vibrant place rather than a traffic node to ensure a mix of activities and users.
  2. Create pedestrian-friendly connections between residential neighborhoods and rail stations.

Related links

About the Research
The research was conducted by Assistant Professor Xinyu (Jason) Cao and research assistant Jessica Schoner of the Humphrey School of Public Affairs at the University of Minnesota and funded by the Transitway Impacts Research Program (TIRP).

Free webinar July 9 on best practices for bicycle trail crossings

Intersections between trails and roadways can be dangerous places for bicyclists and pedestrians. Next week, MnDOT Research Services is offering a free webinar on a forthcoming manual designed to help make trail crossings safer.

On Tuesday, July 9, from 1:00 p.m. to 2:30 p.m. (CDT), University of Wisconsin—Madison Professor David Noyce will be conducting a workshop on his forthcoming handbook, “Decision Tree for Identifying Alternative Trail Crossing Treatments.” The project, funded by MnDOT and the Local Road Research Board, aims to identify current engineering state-of-the-practice for trail crossings and provide guidance as to appropriate crossing designs and vehicular and bicycle right-of-way hierarchies.

You can click on the link below at the specified date and time to watch the webinar. No registration is required.

http://mndot.adobeconnect.com/trailcrossing/

Bridging the gap between research and implementation

The end goal of transportation research, broadly speaking, is to see the results implemented — that is, to transfer the knowledge generated through research to those who can put it to good use. Research Services and the Center for Transportation Studies use a variety of tools to help disseminate research results: our respective websites, email lists, social media, newsletters and this blog, to name a few. But what do we know about how our audiences actually interact with these various channels of communication?

At the Transportation Research Board Annual Meeting earlier this year, researchers from Nebraska presented the findings of a very interesting survey on how engineers and other transportation practitioners prefer to learn about research results. Their presentation, entitled “What Engineers Want: Identifying Transportation Professionals as an Audience for Research,” is available via Slideshare. (Unfortunately, WordPress won’t let me embed it.)

Some key takeaways from the survey:

  • Practitioners overwhelmingly prefer one- or two-page technical briefs to other types of research communication products. (Other popular formats include presentations, video highlights and webinars.)
  • By a wide margin, practitioners use search engines like Google or Bing to seek research results (compared to other options like contacting a colleague or university faculty).
  • Practitioners are mostly interested in information on how to implement findings, as well as cost-benefit analyses of implementation.

The survey results present what I think is a fairly realistic and nuanced picture of the audience for transportation research; they’re also consistent with our (Research Services) own internal research on the issue. The bottom line is that research results need to be condensed into usable bits of information and made easily accessible in a variety of formats. People want information they can use, without having to dig for it. More importantly, they want it in whatever their preferred format is, whether it be print, email, Web, RSS, social media or in-person presentations.

Interestingly, Research Services already produces the kind of two-page technical briefs described in the survey. We call them “technical summaries,” and they are among our most popular products. We generally produce a technical summary for each research project we manage, and post them on our website alongside the full research report. Reading a two-page summary, written in layman’s terms, is certainly easier than poring over research reports that oftentimes number in the hundreds of pages, so it’s not surprising that even those with a strong engineering background prefer the format.

As a side note, last Friday we published a batch of 10 new technical summaries — along with two new transportation research syntheses, which are a type of literature review. Topics range from pedestrian and bicycle safety in roundabout crossings to the effect of intelligent lane control systems on driver behavior. You can check the full list on the Research Services main page.

Now it’s your turn: What forms of communication do you think are most effective at reaching transportation practitioners? Which ones do you prefer? Let us know in the comments.

New fuel cell prototype could power rural ITS applications

Intelligent transportation systems (ITS) technologies can be used to enhance transportation safety and mobility, but the sensors and communications equipment needed for ITS applications typically require access to electricity. In rural areas, limited access to the power grid can make it challenging to implement ITS devices.

Rural intersection roadway lighting
In addition to powering ITS devices, the fuel cells could provide power for rural
intersection roadway lighting. Photo source: http://www.flickr.com/photos/36521983488@N01/175482261/

Current solutions for providing power to off-grid locations include battery packs or diesel generators, both of which require constant maintenance to recharge, refuel, or replace. Other alternatives include solar panels and wind turbines, but cost and performance concerns have limited their use.

“One of the issues with these green power alternatives, such as solar panels, is dependability… especially in the long, cold, and dark Minnesota winters,” says Victor Lund, a traffic engineer with St. Louis County Public Works. Until this technology matures, there is a need for other options that can provide confidence in generating power, Lund says.

To provide a more effective and dependable power alternative, researchers from the University of Minnesota Duluth (UMD) have developed a portable prototype system that uses hydrogen-based fuel cells to generate electricity. The UMD research team was led by chemical engineering associate professor Steven Sternberg, and the project was sponsored by the ITS Institute at the University of Minnesota.

The hydrogen-based fuel cell provides a clean, compact, high-efficiency energy source for an accompanying battery pack, which could be used to operate various ITS devices. The prototype is completely independent of the power grid, works well in cold weather, and requires maintenance only once each week for recharging. The cost of the system is about $7,500, with an additional operating cost of $2,000 per year for fuel materials.

Potential applications include powering variable message signs, dedicated short-range communication technologies, and warning blinkers on traffic signs. According to Lund, the system’s applications extend beyond powering ITS devices. For instance, the fuel cells could be used for rural intersection roadway lighting or as a back-up source for traffic signals in case of a power outage.

Reprinted from CTS Catalyst, June 2013.

Permeable pavements could protect the environment, save taxpayer dollars

KSTP has a nice story today on the Minnesota Department of Transportation’s ongoing research into permeable pavements at the MnROAD research facility. (The video isn’t embeddable on WordPress, but you can find a direct link here.)

Permeable pavements (also known as “porous” or “pervious” pavements) are designed to allow water to pass through roadways and infiltrate directly into the underlying aggregate and soil. Their primary effect is to reduce stormwater runoff, which carries harmful materials from the road’s surface out into waterways. Of course, reducing runoff also mitigates the need for the kinds of costly drainage structures that are normally required to manage stormwater. Permeable pavements also reduce noise and mitigate the potential for hydroplaning, among other documented benefits.

These types of pavements are already used in some areas in Minnesota — mainly in parking lots and city streets — and MnDOT has been studying their potential use for full-depth roadway pavements. As the video indicates, so far the results have been encouraging. (You can read more about MnDOT’s ongoing research on the MnROAD website.)

As a side note, the amount of water these pavements can absorb is quite impressive. Last month, we posted a new Local Road Research Board video on stormwater management. In one scene, a public works crew dumps what appears to be several hundred gallons of water onto a permeable pavement and watch as it disappears almost instantaneously. (Watch the clip here.)

Here are the results of some recent permeable pavement studies here in Minnesota:

Quality-of-life study helps MnDOT evaluate performance measures

As part of a study on transportation and quality of life, MnDOT has partnered with researchers from the University of Minnesota’s Tourism Center to compare current MnDOT performance measures with quality-of-life factors that matter most to Minnesotans.

driver

The evaluation was designed to help MnDOT ensure alignment between the factors that best predict transportation satisfaction among Minnesota citizens and the indicators MnDOT uses to track and measure its performance. The study team was led by Ingrid Schneider, Tourism Center director, and Karla Rains, director of customer relations at MnDOT.

To conduct the evaluation, the research team first analyzed data collected using surveys and focus groups in a previous phase of the quality-of-life study. The data included information on the categories that contribute to quality of life in Minnesota, the role of transportation, and the specific factors or services within transportation that affect citizens’ quality of life.

From these data, the team identified a list of key transportation elements that drive customer satisfaction. Results indicate that the most significant predictors can be grouped into three categories: maintenance/safety, mobility, and transparency. Within those categories, 11 specific items—such as snow and ice removal, road smoothness, commute time, and satisfaction with long-term planning—account for 56 percent of the differences in citizens’ transportation satisfaction.

The team then compared the factors most important to Minnesota citizens with MnDOT’s current performance measures. Overall findings indicate that these existing measures, which track performance in nine major areas, broadly capture much of what is important for Minnesotans’ transportation-related quality of life.

“This was an important key finding for us—we’re already measuring and reporting on many of the things that matter most to our customers,” Rains says. “It was encouraging and comforting to see that.”

In addition to affirming MnDOT’s existing measures, the evaluation identified a few gaps, specifically in the areas of safety, the environment, and transparency.quality

For example, MnDOT typically reports transportation safety in terms of total traffic fatalities and serious injuries from vehicle crashes. However, the quality-of-life study revealed citizen interest in a broader view of traveler safety. As a result, MnDOT plans to include bicycle, pedestrian, and railroad-grade crossing fatality data in future performance measures. “This is already data that we track, but now we plan to add more reporting of fatalities by mode than we have included before,” Rains says.

Based on other study-identified topics of importance, MnDOT plans to add new performance measures focused on air pollution and conduct more reporting of information related to public trust.

“We continue to use this data as guidance in our planning, and it continues to be useful,” Rains says. “We want to make sure we’re listening and measuring ourselves against the things that are most important to our customers.”

Reprinted from CTS Catalyst, June 2013.

About those roundabouts

One of my unofficial duties as a MnDOT employee is to respond to a near-constant barrage of opinions from my family and friends regarding the condition of our state’s roadways. (My wife, for example, half-jokingly tries to ascribe personal responsibility to me for the congestion she faces on her morning commute.) Interestingly, one of the issues that gets brought up to me most often in private conversations is roundabouts — the circular intersections that are widely praised by engineers but often vilified by a skeptical public.

From a public interest perspective, the verdict on roundabouts is overwhelmingly positive. With very few exceptions, roundabouts have been shown to dramatically reduce both the frequency and seriousness of traffic accidents when compared to other types of intersections. One oft-cited source, the National Insurance Institute for Highway Safety, reports that U.S. intersections converted to roundabouts have experienced a 35-47 percent decrease in crashes and an 72-80 percent decrease in injury crashes (source here). Moreover, because the don’t have stop signs or traffic lights, roundabouts have been found to reduce traffic delays and pollution.

Perhaps not surprisingly, research on these potential benefits has precipitated a rash of roundabout construction. In Minnesota alone, 115 have already been built, with another 39 either planned or under construction, according to the Pioneer Press. Love them or hate them, roundabouts are becoming a fact of life here.

Of course, not everyone loves them. In spite of their stellar  record, roundabouts remain something of a political lightning rod. This article in the Mankato Free Press and this news segment from KSTP provide typical examples of the kind of skepticism officials face when proposing to put in a roundabout. The problem is persistent enough that many officials see a need to develop a public relations game plan. On June 19, the Transportation Research Board is offering a free webinar entitled “Community Outreach: Successful Outcomes for Roundabout Implementation,” designed to help transportation professionals understand and respond to political opposition to roundabouts. It’s free for employees of TRB sponsor organizations (including MnDOT); a $99 registration fee is required for employees of non-sponsors.

For those who are unfamiliar with roundabouts, there are some good resources designed to help people understand their purpose and benefits. Several years ago, the Local Road Research Board produced the video above (along with an accompanying brochure). MnDOT also has a resource page devoted to explaining the use of roundabouts.

Those with more than a passing interest in the subject might also want to check out these recent MnDOT/LRRB-sponsored studies:

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