November 2011 – Vol. 5, No. 4 Partnering for Roadway Innovation

TERRA E-News is a quarterly electronic newsletter of the Transportation Engineering and Road Research Alliance. TERRA E-News brings you the latest research on pavement, materials, and related transportation engineering challenges, including issues related to cold climates.

MEMBER NEWS

New Member: Iowa Department of Transportation

The Iowa Department of Transportation joined TERRA in June after informally sharing information and ideas with TERRA for the past few years. The Iowa DOT hopes to better manage available research resources and to address issues that have a regional or national interest through its TERRA membership. Mark Dunn, operations research engineer, represents the Iowa DOT on the TERRA board.

The Iowa DOT’s history with transportation research dates back to 1919, when Iowa’s State Highway Commission was established at Iowa State College (now Iowa State University). The Iowa DOT continued to stay on the leading edge of innovations in materials, processes, and technology to bring improvements to Iowa’s transportation system with the creation of the Iowa Highway Research Board program in 1950.  Currently, the Iowa DOT’s main research areas are transportation safety, portland cement concrete (PCC) pavements, winter maintenance, bridges and structures, human factors, and intelligent compaction/construction in soils and geotechnical construction.

Iowa’s success in transportation research is a result of the collaboration of a small core of Iowa DOT research staff with numerous other experts and agencies across Iowa and the United States, including DOT technical staff, Iowa’s city and county engineers, university researchers, and industry partners. 

“Our past collaboration efforts with most, if not all, of the other TERRA members have given us the confidence that our participation in TERRA will be a great benefit to Iowa DOT and to the other TERRA members,” Dunn said.

Member Research Spotlight: Pavement markings and safety in Iowa

Each TERRA member organization will have an opportunity to briefly share and showcase a specific research project or initiative in the Member Research Spotlight. Profiles of most TERRA member organizations, previously published here, remain available through the TERRA E-News archives. The Iowa Department of Transportation provided details about this edition’s featured research project.

Problem

In Iowa and other states with significant amounts of snowfall, the reflective beads embedded in roadway paint get worn and scraped up by snowplows over time. As pavement markings wear out, it is necessary for agencies to restripe and repair them on a regular basis. But how often should a marking be restriped to keep drivers safe?

Previous safety-focused research on pavement markings has examined retroreflectivity variability, the relationship between retroreflectivity and driver visibility, and pavement marking improvements and safety. However, a significant statistical correlation between retroreflectivity and crashes is undefined to date.

Solution

The Iowa DOT has completed a study investigating a possible statistical relationship between pavement marking retroreflectivity and crash occurrence probability. The study included an analysis of five years of pavement marking retroreflectivity data collected by the Iowa DOT on all state primary roads and corresponding crash and traffic data. A spatial-temporal database was developed using statewide crash data and measured retroreflectivity data to account for the deterioration of pavement markings over time.

Retroreflectivity was found to have a significant effect on crash occurrence probability for four data subsets—interstate, white edge line, yellow edge line, and yellow centerline data. For white edge line and yellow centerline data, crash occurrence probability was found to increase as values of retroreflectivity decreased.

Implementation

These findings provide a statistical link between pavement marking retroreflectivity levels and crash history in Iowa. Along with the Federal Highway Administration’s proposed minimum retroreflectivity standards, these findings support increased investment in marking application and maintenance. The study’s results also serve as a foundation for performance measures and future material placement and selection guidance for Iowa’s maintenance personnel.

Project Partners

This project was funded by the Iowa Highway Research Board.

More Information

• Pavement Markings and Safety Tech Brief (111 KB PDF)
• Pavement Markings and Safety Final Report (2.0 MB PDF)
• Contact: Bob Younie, 515-239-1589, Bob.Younie@dot.iowa.gov

PROJECTS AND INITIATIVES

MnROAD research conference showcases breadth and depth of national partnerships

Researchers shared results of several TERRA-initiated pooled-fund and other research studies from MnROAD’s Phase Two Initiative during a daylong research conference October 4 in Minneapolis. Many of the research findings on pavement materials, design, construction, and rehabilitation are ready to be implemented in Minnesota and around the country.

The event was part of a larger organizational undertaking over three days that included a quarterly TERRA board meeting and technical advisory panel (TAP) meetings for seven MnROAD pooled-fund projects. Combining meetings with the conference afforded unprecedented regional, national, and international opportunities for networking and collaboration among TERRA members and friends.

The research conference—a TERRA Innovations Series event—featured 22 research presentations and bus tours of MnROAD. TERRA hosted the conference in cooperation with the Minnesota Department of Transportation (MnDOT) and the Minnesota Local Road Research Board, both TERRA members.

More than 160 attendees from at least 13 states and Norway included state DOT engineers and technicians, city and county engineers, Federal Highway Administration officials, Norwegian Public Roads Administration representatives, consulting engineers, contractors, and others interested in pavement research and implementation.

The conference emphasized how lessons learned from research at MnROAD have been and can be implemented to build better, more cost-effective pavements. Sessions focused on recycled materials, pavement rehabilitation, preventive maintenance, long-life pavements, surface characteristics, and other pavement innovations.

TERRA co-chair André Clover, administrative engineer with the Michigan Department of Transportation (MDOT), and Ben Worel, MnROAD operations engineer, welcomed attendees to the research conference. Worel, along with fellow MnROAD engineers Tim Clyne and Tom Burnham, provided an overview of MnROAD research activities.

Worel and Clyne also led two bus tours to MnROAD. Each tour group visited test sections on the mainline, the low-volume road, and the farm loop to view projects studying full-depth reclamation, innovative diamond grinding of road surfaces, porous and pervious pavements, composite pavements, the effects of farm implements on low-volume roads, and other areas. In addition, unique and leading-edge non-destructive testing equipment was demonstrated as part of the tour.

MnROAD, originally constructed in 1994, began its Phase Two Initiative in 2007 and has since reconstructed nearly 40 test cells. During the past year, two new test cells were constructed and three were rehabilitated. Since its founding in 2004, TERRA has lead the transformation of MnROAD into a leading regional, national, and international outdoor pavement research facility.

The broad involvement in the MnROAD research conference and related meetings marks a milestone in the growth of the TERRA organization, with interest, participation, and partnering activity reaching a new high. Nearly 40 participants in the TAP meetings for the MnROAD pooled-fund projects held in conjunction with the conference came from outside Minnesota. Each of those research projects was initiated through TERRA. In addition, the TERRA board meeting drew 31 attendees in person—the most ever—with the remaining member representative joining via teleconference.

The event was the fifth in the TERRA Innovation Series, which began in 2007. Previous events featured the reconstruction of Highway 36 through North St. Paul, MnROAD research partnerships, transportation assets management (held in Grand Rapids, Michigan), and sustainability in transportation (held in Madison, Wisconsin). The events have a technical focus and address research results, trends that affect or improve productivity, innovative partnering and contracting models, and hot topics that may lead to new research related to TERRA priorities.

Related resources:

• TERRA Innovation Series: MnROAD research conference event page
• Minnesota Road Research Project (MnROAD) facility
• MnROAD Phase Two Inititative projects

 

Portable weigh station for rural roads debuts at MnROAD

In August, the Minnesota Department of Transportation (MnDOT) hosted a demonstration of a portable weigh-in-motion (WIM) system at the MnROAD pavement research facility near Albertville, Minnesota. The system, designed by University of Minnesota­–Duluth electrical and computer engineering professor Taek Kwon, promises to make it easier and less expensive to monitor truck traffic, especially in rural areas.

In recent years, state, county, city, and township transportation authorities have grown more concerned about damage to local roads and bridges due to the increased traffic of larger, heavier trucks. The need for better data about vehicle loads became critical when a new state law in 2009 considered all paved roads to have a 10-ton design unless posted otherwise.

Minnesota has 16 WIM stations, with another scheduled to open near Moorhead next month. All but one are located on a principal arterial route. “There’s a lot of area that we’re not really covering, and a portable weigh-in-motion system would be useful,” said Ben Timerson, weight data and engineering coordinator at MnDOT.

“Truckers fairly rapidly figure out where the permanent sites are and learn how to avoid them.”

Timerson, who hosted MnROAD demo, said a portable WIM system would aid the Minnesota State Patrol in weight enforcement, and the additional freight data would be useful for managing the county road system, designing appropriate pavements, and setting bridge load restrictions.

Kwon’s portable WIM system, developed after testing several configurations, currently comprises two 24-foot-long sensor strips, each about 12 inches wide and connected to a battery-powered computer controller that calculates the vehicle load using software Kwon also created. The heart of the design is a pressure sensor consisting of a thin strip of piezoelectric material, which converts mechanical pressure into a measurable electrical signal. The sensors, which are spaced 10 feet apart and stretch perpendicularly across two lanes of traffic, typically are fastened to the pavement with a few concrete screws and tape.

Kwon said the system is most effective on a smooth, well-maintained paved surface. In addition, the system is intended for use only in dry weather conditions.

The research to develop the portable WIM system has been sponsored by MnDOT. In addition, MnDOT State Aid and the Minnesota County Engineers Association have supported the research, with several county engineers serving on the technical advisory panel for the project. Eventually, the plan is to contract with a manufacturer to produce a commercial version of the system.

Related resources:

• Development of a Weigh-Pad Based Portable WIM System project page
• About researcher Taek Kwon

 

 

Pervious concrete researcher shares findings, tips for cold regions

Earlier this year at the Center for Transportation Studies annual research conference, University of Minnesota civil engineering researcher Mary Vancura presented more findings from a TERRA-initiated study of the cold-weather performance of pervious concrete. Vancura discussed the ways pervious concrete can go wrong and what solutions may help prevent failure.

Pervious concrete allows water to seep through it via tiny passages and holes in the concrete. This is helpful in areas where water tends to accumulate or could not return to the ground with regular concrete in place. But the special nature of pervious concrete also presents a unique set of problems. Vancura explained that three things can go wrong with pervious concrete: impermeability, raveling, and cracking. Impermeability is usually the result of dirt and debris, usually from trees, getting lodged in the holes of the concrete. This is easily avoided with regular maintenance using any machine with a high-powered vacuum or a power washer to dislodge the debris. Raveling, which is when the top aggregate layers separate, is often due to debonding of the concrete and aggregates and can affect just the first two layers or deeper layers. Cracking is similar to what happens to regular concrete, although the nature of pervious concrete means that it cannot withstand heavy loads, like garbage trucks, on a regular basis. This is why pervious concrete is best used in low-volume applications, such as alleys, parking lots, or recreational paths, she said.

As part of her research, Vancura took samples of pervious concrete from 22 sites around Minnesota. She found that deeper raveling tended to happen when poor quality aggregate was used or when the concrete got too dry. She also noticed that air was often not properly entrained in the concrete.

Vancura and her colleagues also conducted a small experiment by placing pervious concrete at the edge of a parking lot. One section was a standard mix pervious concrete, one section contained extra viscosity-modifying admixture, which made a stiffer paste, and one section had light-weight aggregates, which can absorb water and regulate hydration of the paste. Luck was not on her side the day Vancura and two other installers laid the concrete. It was a cold day in November with winds up to 40 miles per hour. The truck with the cement got lost, and the concrete sat in the truck for approximately an hour and a half. The team also had to contend with equipment malfunctions. After a harrowing day, the team laid insulating blankets over the concrete to trap heat (as the temperature was predicted to dip to 32 degrees F after dark) and prevent evaporation (from the high winds).

When Vancura revisited her concrete after five months, she found it had not only survived the winter—it looked great. She attributed the outcome to the use of the insulating blankets during the curing period, as well as the extra time the cement spent in the truck, allowing the even distribution of water.

University of Minnesota civil engineering professor Lev Khazanovich is the principal investigator of the study along with co-investigator Kevin MacDonald of Cemstone. The Aggregate & Ready Mix Association of Minnesota (ARM) partnered with the University of Minnesota Department of Civil Engineering to obtain a research grant from the Ready Mixed Concrete (RMC) Research & Education Foundation for the study. Much of the research has been conducted using pervious concrete systems at MnROAD. ARM, the RMC Research & Education Foundation, and the University of Minnesota are TERRA members.

Research on pervious concrete and its applications is ongoing, as it is still a relatively new approach in cold climates.

Related resources:

• Download presentation slides (3.2 MB PDF)

ANNOUNCEMENTS

TERRA Pavement Conference scheduled for Feb. 9, 2012

The TERRA Pavement Conference is scheduled for February 9, 2012, at the University of Minnesota Continuing Education and Conference Center in St. Paul, Minnesota. This one-day conference provides practical information to practitioners and others interested in pavement design, construction, rehabilitation, and maintenance. The emphasis of the conference is new materials and methods that can assist decision makers in providing the most cost-effective strategies for building, repairing, and maintaining pavement infrastructure. The conference agenda and registration information will be posted on the conference web page in December.

The conference is intended for researchers, city engineers, county engineers, public works officials, maintenance superintendents, design engineers, consulting engineers, and others interested in pavement issues. The conference agenda and registration information will be posted in December.

For more information about the 2012 TERRA Pavement Conference, contact Stephanie Malinoff, malinoff@umn.edu or 612-624-8398, or visit the event web page. To view information from previous conferences, visit the TERRA events page.

CPAM upcoming events

The Concrete Paving Association of Minnesota (CPAM) calendar includes these upcoming events:

• APWA Minnesota Chapter Fall Workshop and Conference,
  November 16–18, 2011
  Earle Brown Heritage Center, Brooklyn Center, Minnesota
• American Concrete Pavement Association (ACPA) Annual Meeting,
  November 30–December 2, 2011
  Hyatt Grand Champions Resort, Indian Wells, California
• 61st Annual Concrete Conference, December 8, 2011
  University of Minnesota, St. Paul, Minnesota
• CPAM Annual Concrete Paving Workshop, March 8–9, 2012
  Mankato, Minnesota
• APWA Minnesota Chapter Spring Conference, May 9-11, 2012
  Grand View Lodge, Minnesota

MAPA upcoming events

The Minnesota Asphalt Pavement Association (MAPA) calendar includes these upcoming events:

• MAAPT 58th Annual Asphalt Conference, December 7, 2011
  Doubletree Hotel, St. Louis Park, Minnesota
  Info: info@mn-aapt.org
• 56th Annual Asphalt Contractors’ Workshop/Quality Initiative Workshop, March 6, 2012
  Earle Brown Heritage Center, Brooklyn Center, Minnesota
  Info: info@mnapa.org
• NAPA 57th Annual Membership Meeting, January 22-25, 2012
  JW Marriott Desert Springs Resort, Palm Desert, California
• World of Asphalt Show & Conference, March 13-15, 2012
  Charlotte Convention Center, Charlotte, North Carolina
• AAPT 87th Annual Meeting, April 1-4, 2012
  Omni Austin Hotel Downtown, Austin, Texas
  Info: aaptinfo@gmail.com

ATSSA annual convention and traffic expo, Feb. 12–16, 2012

The American Traffic Safety Services Association (ATSSA) 42nd Annual Convention and Traffic Expo is scheduled for February 12–16, 2012, at the Tampa Convention Center in Tampa, Florida.