U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
|Accelerating Infrastructure Innovations|
Publication Number: FHWA-SA-96-012
Date: January 1996
The Federal Highway Administration (FHWA) has concluded its Test and Evaluation Project 22 on the Georgia digital faultmeter. Eighteen State departments of transportation and the American Concrete Paving Association participated in the study. The majority of participants found the digital faultmeter to be a significant improvement over other methods.
The Georgia digital faultmeter, designed by the Georgia Department of Transportation (DOT), is a hand-held device that measures faulting--the vertical displacement at joints-- in portland cement concrete pavements and the drop-off between the pavement surface and the adjacent shoulder surface. Changes in joint faulting and lane-to-shoulder drop-off over time are important indicators of pavement performance.
The device was studied and modified under the Strategic Highway Research Program (SHRP). The Georgia DOT built five faultmeters at FHWA's request, and these were loaned to States for evaluation. FHWA provided limited funding to State highway agencies participating in the test and evaluation project.
The Georgia faultmeter is easy to use and weighs only 3.2 kg (7 lb). The operator holds the meter in his or her right hand when testing the outside lane and in the left hand when testing the inside lane, as this allows the operator to stand facing traffic. An arrow on the meter points in the direction of traffic flow to make sure the operator is holding the device correctly. The legs of the meter are placed on the leave, or far, side of the joint. A probe is then placed in contact with the slab on the approach, or near, side. The operator presses a button and a digital reading in millimeters appears in the display unit. A positive number indicates that the slab on the leave side is lower; a negative number indicates the slab on the leave side is higher.
Thirteen of the 18 participating organizations reported that the faultmeter was an improvement over their current methods. Those reporting the faultmeter to be an improvement were using a ruler, a straightedge, calipers, or other gauges for measuring faults. The majority of participants reported that the Georgia faultmeter is easy to use, light and compact, efficient, accurate, and faster than other methods.
The Maryland Department of Transportation reported that the digital faultmeter was more efficient than their present method, which required two people to perform the tests--one to take the tests and one to record the measurements and watch for traffic.
The Georgia faultmeter was also reported to be safer than most other methods. When measuring faults with rulers, straightedges, calipers, or fault gauges, the operator has to get down on hands and knees to measure the faulting; the road also has to be closed to traffic or controlled. With the Georgia faultmeter, engineers no longer have to hunch over to get a reading. In fact, they get a measurement in a matter of seconds, and the number remains on the display so that it can be read from the safety of the roadside later. The faultmeter is also faster and more efficient, and it does not require traffic control.
Judith Corley-Lay, State pavement analysis engineer for the North Carolina Department of Transportation, and one of the participants in the evaluation, says the safety benefit is a big plus. "You're very vulnerable when you're bent over near traffic," says Corley-Lay. "When we used the straightedge rule, I ended up aching all day from bending over. This is such an improvement--it's so quick and easy."
The participating highway agencies also suggested additional uses for and improvements to the device. The Indiana Department of Transportation suggested that the faultmeter be used to measure paint thickness on the road surface. Another suggestion was that efficiency could be increased if data points could be saved and recorded by the faultmeter, rather than having to be transcribed.
The California Department of Transportation, which currently uses its own version of a faultmeter developed in the 1960s, said it will modify its device to include some of the innovative concepts featured in the Georgia faultmeter. For example, California is going to incorporate the hold feature, which allows the operator to "freeze" the measurement in the display for reading later.
The North Carolina DOT is presently recalibrating three of the faultmeters used in the evaluation project to read to one-tenth of a millimeter, rather than to the nearest millimeter. The Utah Department of Transportation will receive one of the modified devices, and North Carolina will retain the others. The two remaining faultmeters are currently used in the National Highway Institute's distress identification course.
The digital faultmeter is now commercially available at a cost of approximately $1,680.
For more information about FHWA's Test and Evaluation Project 22, call Evan Wisniewski in FHWA's Region Four Office, 404-347-4075 (fax: 404-347-2125). For information about the National Highway Institute's distress identification course, call Pete Parsons, course coordinator at 703-235-0529.