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Publication Number: FHWA-HRT-06-023
Date: March 2006
Now providing a high-speed alternative for evaluating highway pavements is the Federal Highway Administration's (FHWA) new Rolling Wheel Deflectometer (RWD). The RWD is a specially designed tractor-trailer with laser measuring devices mounted on a beam under the trailer and a computerized data collection system contained in the cab. The device can measure pavement deflections while traveling at highway speeds of up to 100 km/hr (70 mi/hr). Data can be collected on 320 to 480 km (200 to 300 mi) of roadway per day, usually without the need for traffic control vehicles. "The primary use for the RWD is to scan roadways for areas with high and variable deflections. These areas would then be targeted for more detailed inspection and testing using a falling weight deflectometer, coring, or other types of testing," says Thomas Van of FHWA. "With an RWD, agencies can concentrate resources on those areas most needing attention."
During the past year, FHWA has tested the RWD in Indiana, Kentucky, Minnesota, New Jersey, Ohio, Virginia, and West Virginia. These tests were designed to familiarize State departments of transportation and others with the RWD. FHWA's review of the test data to date has confirmed the original design criteria for the device. "Comparison of the RWD data with that from falling weight deflectometers has also been remarkably good," says Van. In addition to the State demonstrations, testing has been conducted on the entire length of the Natchez Trace Parkway, which runs through Alabama, Mississippi, and Tennessee, and at the National Center for Asphalt Technology test facility in Alabama, the Minnesota Road Research Project facility in Minnesota, and the Smart Road in Virginia. "Each testing program had unique objectives, and each agency has different plans for using the RWD data," says Van. New Jersey, for example, is considering using the data in conjunction with its pavement management system (PMS), while Minnesota is looking at using it to identify seasonal load restrictions on its roadways.
"We are now working to identify ways that RWD information can be effectively used in a PMS and to develop an analytical process to link the deflections to remaining service life and other pavement performance measures," notes Van. The goal of these efforts is to demonstrate that the RWD is a cost-effective tool that State transportation departments and others can use to help manage highway pavements. FHWA will continue testing and demonstrating the RWD this year, including tests planned for California, Iowa, and Kansas.
For more information about the RWD or scheduling a demonstration or test in your State, contact Thomas Van at FHWA, 202-366-1341 (email: firstname.lastname@example.org).
Photo 5. The Rolling Wheel Deflectometer is a specially designed tractor-trailer with laser measuring devices mounted on a beam under the trailer.
Photo 6. A computerized data collection system contained in the cab.
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