May 2017 Vol. 5, No. 4

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Full-depth reclamation is cost-effective for urban, suburban roads

Image of full-depth reclamation of asphalt pavement

Photo: MnDOT

A new study by University of Minnesota researchers indicates that full-depth reclamation (FDR) of asphalt pavement is a superior method of rehabilitating urban and suburban roadways, outperforming traditional mill-and-overlay in cost and durability over a 35-year period. The researchers also developed performance-based specifications.

Currently, FDR is often used on rural roadways to reduce costs for materials and hauling. With FDR, road builders use trains of recycling equipment to pulverize, lift, grind, remix, and repave asphalt in a single pass. This recycling puts less demand on petroleum resources and new aggregate.

Despite its benefits, FDR has yet to be adopted widely by city and county public works departments. In part, this is due to the challenge of using trains of equipment on urban and suburban roads that feature curbs, manholes, and driveways. Mill-and-overlay also has lower initial costs.

“Our goal was to provide evidence of FDR’s cost-effectiveness, guidelines for FDR project selection, and, ultimately, performance-based specifications,” says Mihai Marasteanu, a professor with the Department of Civil, Environmental, and Geo- Engineering and the study’s principal investigator.

The study, sponsored by the Minnesota Local Road Research Board and the Minnesota Department of Transportation, validates the assertion that FDR is a viable and cost-effective option for urban and suburban asphalt pavement rehabilitation. “Before, all we had was anecdotal information,” Marasteanu says. “Now we have laboratory-testing methods that are easy to use and can be incorporated in performance prediction models.”

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Innovation resources available; St. James mini-roundabouts

EDC logo

The Federal Highway Administration offers resources to help states and their partners deploy the innovations in Every Day Counts round four (EDC-4). Another resource, the Accelerated Innovation Deployment (AID) Demonstration program, awards funding of up to $1 million for highway projects that use proven innovations in any project phase.

A project in St. James, Minnesota, is one of 62 projects that received an AID Demonstration grant. The project will fund the construction of two interconnected mini-roundabouts on Minnesota State Highway 4 (1st Avenue) and back-in diagonal parking. The mini-roundabouts are part of a larger urban reconstruction project of Highway 4 through St. James and will replace signals at both intersections. Mini-roundabouts are part of the EDC initiative on Intersection/Interchange Geometrics.

FHWA formed deployment teams for each EDC-4 innovation to provide the transportation community with information, technical assistance, and training, including workshops and peer exchanges.

The State Transportation Innovation Council (STIC) Incentive program provides up to $100,000 a year per state to help STICs make innovations standard practices.

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Converting paved roads to unpaved: best practices

Image of NCHRP cover

Many roads with very low traffic volumes can be maintained more economically and at a higher level of service with an unpaved or granular surface. A new synthesis from the National Cooperative Highway Research Program (NCHRP) summarizes the state-of-the-practice of the road conversion process, tools that can be used to aid in the decision-making process of whether to convert from paved to unpaved, and what has worked and what has not worked for those in the unpaving process.

The study found that the practice of converting paved roads to unpaved is relatively widespread: Recent road conversion projects were identified in 27 states. These are primarily rural, low-volume roads that were paved when asphalt and construction prices were low. Those asphalt roads have now aged well beyond their design service life, are rapidly deteriorating, and are both difficult and expensive to maintain. Many local road agencies are converting these deteriorated paved roads to unpaved as a more sustainable solution.

Key findings from the study include:

  • Local road agencies have experienced positive outcomes by converting roads. Many local road agencies reported cost savings after converting, compared with the costs of continuing maintenance of the deteriorating paved road or repaving.
  • One key to successful conversion is early involvement of the public in the planning process.
  • Other techniques that can be used to improve the overall results of a project include treating or stabilizing granular surfaces to control dust, limiting the rate of aggregate loss, and reducing motor grader/blade maintenance frequency.
  • Stabilization procedures can also improve safety, increase public acceptance, and reduce life-cycle costs and environmental impacts after a conversion has taken place.

The document also provides a summary of relevant reports, documents, and resources that can be used when considering or conducting a road conversion.

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Calculator estimates the effectiveness of swales

Image of swales

U of M researchers have developed a simplified calculator for estimating the stormwater infiltration capacity of swales. The MnDOT-sponsored research illustrates that more infiltration occurs in a swale’s side slopes than origi­nally thought. By giving more complete credit for the infiltration provided by the side slopes, this calculator will reduce the need for more costly stormwater management programs.

The use of grassed swales, including roadside drainage ditches, is an inexpensive and effective stormwater management practice. These vegetated roadside surfaces cap­ture and infiltrate stormwater close to its source, reducing the quantity of pollutants and volume of stormwater car­ried off-site to receiving waters.

Although nearly a dozen factors affect swale infiltration, the investigators were able to develop and verify a simplified dry swale calculator for Minnesota that accurately estimates volume reduction based on only four factors: saturated hydraulic conductivity of the soil, width of the swale, width of the road, and the location’s rainfall volume percentile as a function of rainfall depth. This calculator accounts for infiltration of both the side slope and the bottom channel of the swale.

“The study verified that there is much more infiltration in the side slopes than previously thought,” says Professor John Gulliver of the University of Minnesota, the lead researcher. “This is a significant shift from current theory.”

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Protect workers from excessive heat

Screenshot of Osha heat ad

Any worker exposed to hot and humid conditions is at risk of heat illness, especially those doing heavy work tasks or using bulky protective clothing and equipment. Some workers might be at greater risk than others if they have not built up a tolerance to hot conditions, including new workers, temporary workers, or those returning to work after a week or more off. Guidance and resources are available for employers and workers.

According to US OSHA, an employer with workers exposed to high temperatures should establish a complete heat illness prevention program:

  • Provide workers with water, rest, and shade.
  • Allow new or returning workers to gradually increase workloads and take more frequent breaks as they acclimatize, or build a tolerance for working in the heat.
  • Plan for emergencies and train workers on prevention.
  • Monitor workers for signs of illness.

Heat illnesses can be as much of a problem in Minnesota as in other regions of the country. This is because people usually do not have the opportunity to become and stay acclimatized in climates such as Minnesota's, where daily high temperatures can vary up to 30 degrees from one day to the next during the summer.

Minnesota's heat stress standard is designed to protect employees against the risk of heat-induced illnesses and unsafe acts. A 14-page heat stress guide from the Minnesota Department of Labor & Industry’s Occupational Safety and Health Division has sections on heat disorders, prevention, evaluation, control, and training.

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Resources on OSHA's heat illness website in English and Spanish, including:

  • Illustrated, low-literacy fact sheets
  • Worksite training poster
  • Heat illness prevention training guide
  • An app to download to your phone to calculate the heat index and provide recommendations based on your risk level

Resources on the Minnesota Department of Labor & Industry site: