Since June, four heavily-laden driverless trucks have been traveling an average of 15 hours a day around a 2.9-km (1.8-mi) oval test track in the Nevada desert. The trucks are guided by wires buried in the hot-mix asphalt pavement. By applying 10 million equivalent single-axle loads in 2 years, the trucks will simulate 10 or more years of Interstate-level traffic loads on the pavement. The purpose: to test how well 21 variations of a typical asphalt mix hold up under the extended heavy loads.
This experiment, known as WesTrack, was built and is being operated by a consortium of seven organizations, each with a specific role in the project.
To herald the start-up of this $12 million project and to give highway engineers, contractors, materials suppliers, and the media a first-look at its operations, the WesTrack team held an "open house" in June. More than 200 people toured the project site, located 100 km (60 mi) southeast of Reno.
Calling WesTrack "the test road for the next century," Tony Kane, executive director of the Federal Highway Administration (FHWA), highlighted the project's emphasis on quality, partnerships, and leadership. "We are trying to close the gap, to elevate the state of the practice to the state of the art," said Kane. "That's what this track is all about."
Frank Francois, executive director of the American Association of State Highway and Transportation Officials, stressed the importance of validating the Superpave system. "The ultimate question is, how does the Superpave system actually work on the road? That's what we're finding out here at WesTrack. This is a world-class facility, and it will be carefully watched by highway agencies throughout the world."
The goal of the project is to advance construction technology in ways that will ultimately help roadways last longer, perform better, and cost less. The project has two primary objectives: to further the development of performance-related specifications for hot-mix asphalt construction and to validate the Superpave mix design and analysis procedures. (see December 1995 Focus). It particularly focuses on the construction and materials factors that are expected to have the greatest effect on performance (aggregate gradation, air void content, and asphalt content).
Sensors in the test track continually monitor the pavement's temperature and loads. In addition, each pavement section is evaluated at regular intervals using five performance measures:
"Some sections already have a half-inch [13 mm] of rutting," says Steve Seeds of Nichols Consulting Engineers. "That's in line with what we expected, since those test mixes were designed with too much asphalt, making them prone to permanent deformation."
Tom Stephens, director of the Nevada Department of Transportation (DOT), called the Superpave system "a massive breakthrough in asphalt technology." Nevada DOT is already designing and constructing Superpave pavements. "The State of Nevada is committed to implementing the Superpave system," said Stephens. "By being early users, we'll be out in front in taking advantage of this new technology that will lead to more durable roads and long-term cost savings."
Some members of the press present at the open house questioned whether the Superpave system would solve Reno's pothole problems on residential streets. A recent poll of Reno residents had found potholes to be the number-one problem in Reno. FHWA's Joe Toole responded, "We realize that our local roads provide the links to our Nation's highway system, and as such are critical lifelines in keeping our economy moving. Ultimately, this new technology will be just as useful for local roads as for Interstates. But our first interest is in assuring that the technology is sound and proven. I expect the University of Nevada's Local Technical Assistance Program will eventually take this technology and move it to the local level here in Nevada."
For more information about WesTrack, contact Colin Ashmore at the Nevada Automotive Test Center (telephone: 702-629-2000; fax: 702-629-2029) or Terry Mitchell at FHWA (telephone: 703-285-2434; fax: 703-285-2767).
The Western Regional Superpave Center, located at the University of Nevada, Reno (UNR), held its official opening on June 5, in conjunction with the WesTrack open house. The UNR facility, one of five such regional centers, will work in close partnership with the Nevada Department of Transportation, the University of California at Berkeley, the Rocky Mountain Asphalt User-Producer Group, and the Pacific Coast Asphalt User-Producer Group. The center will serve 12 States and 2 Canadian Provinces.
According to Jon Epps, the center's director, "A key role of the center will be to provide training on the Superpave system. The center will also assist highway agencies and contractors with new analysis procedures for pavement performance testing."
Frank Francois, executive director of the American Association of State Highway and Transportation Officials, also spoke at the center's opening. "This center is an important keystone to reaching full implementation of the SHRP asphalt research," said Francois. "Deployment and implementation of the entire Superpave system is a major undertaking. To make it happen, we have to work with public- and private-sector engineers, suppliers, and contractors. The Superpave centers are critical to that effort."
Dale Decker, vice president of research and technology at the National Asphalt Pavement Association, echoed Francois's comments. "Regional and local support is critical to the centers' success at validating the Superpave performance models," said Decker. "The centers can also play a critical role in technician training. We must press forward to implement those technologies that are ready, refine those that are not quite ready, and identify any that are inappropriate for practical application."
Pavement Quality is Public's Number-One Concern
A recent survey conducted on behalf of the National Quality Initiative asked motorists to rate the Nation's highway system and to prioritize highway improvements. The more than 2,000 respondents ranked "pavement condition" as the top priority for improvement. The report states:
It is clear that the top priority for improving the nation's highways is to focus on the quality of the roadway surface. This is the factor that will most significantly increase public satisfaction with the highway system.
The survey was administered in fall 1995, by Coopers & Lybrand L.L.P. Funding was provided by FHWA. Copies of the survey report, National Highway User Survey, May 1996, are available from Frank Bednar at FHWA (telephone: 202-366-8027; fax: 202-366-9981). The survey report can also be downloaded from the World Wide Web (htpp://www.avalon-ais.com/nqi/nqi.htm).
The WesTrack team consists of seven organizations:
University of California at Berkeley-Superpave hot-mix asphalt accelerated performance testing.
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