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|Federal Highway Administration > Publications > Public Roads > Vol. 61· No. 5 > It Takes More than Mirrors to See Your True Profile|
It Takes More than Mirrors to See Your True Profile
by Dennis G. Sixbey
It was a perfect October day in 1997 when a Penn State professor and researchers from all over the world gathered at the Turner-Fairbank Highway Research Center (TFHRC) in McLean, Va., to perform a critical step in an experiment to measure road evenness.
TFHRC, the home of the Office of Research and Development for the Federal Highway Administration (FHWA), hosted Professor James Wambold, who, with his fellow Penn State professor J.J. Henry, is heading up an experiment that will compare the results of measurements carried out using different equipment and different measurement methods. Wambold and Henry plan to carry out parts of the experiment in Arizona, Japan, and The Netherlands/Germany in 1998.
They will present their findings at the October 1999 meeting of the Permanent International Association of Road Congresses (PIARC) in Kuala Lumpur, Malaysia. The work will fall under the jurisdiction of PIARC's Committee 1 on Surface Characteristics, which Henry chairs.
But before any of that could take place, Wambold came to TFHRC for an all-day test of potential equipment the professors might use in their experiment. Wambold represented the team, as Henry was unable to attend.
The professors were specifically seeking equipment that could best measure "true profile," which is a profile of a road using measurements taken in both longitudinal and transverse directions. Once "true profile" is obtained, researchers can make thorough predictions about the character of pavement surfaces, Wambold said in a recent interview.
There was plenty of response to the professors' challenge to find the best equipment to measure true profile. Gathered with Wambold on Oct. 20, 1997, were corporate and government representatives from several U.S. states, as well as from the countries of Australia, Denmark, Japan, The Netherlands, Sweden, and the United Kingdom. Each brought along a piece of equipment for the professors to evaluate.
"That was an exercise to help select the devices we were going to use," Henry said in a recent interview. "It was an extremely important step (in the research)."
TFHRC staff set up a variety of sites for the test day. Some were rough (surface) sites; some were very smooth; and others in-between. Each piece of equipment was tested on each type of site.
All these pieces of equipment were run through a battery of tests to make sure they could cover the full range of what they would be asked to do in the three locations - Arizona, Japan, and The Netherlands - where Wambold and Henry are continuing their experiment.
The professors wanted to push each piece of equipment to the limit during the testing at TFHRC. They required not only a variety of surfaces, but they also wanted the different surfaces to contain a variety of features, such as rippling, rutting, and wheel-track wear. Each of the three regions will run tests in the same way.
Wambold said the professors were pleased with the test sites at TFHRC.
"We had good sites, and I think everyone was impressed with what we were doing there," he said. "We got what we were looking for."
Following the TFHRC experiment, the professors selected three types of equipment to use in their research. One is a "rod-and-level," which measures large distances of pavement. One rod-and-level measurement is taken every 30 meters. The second is a "static inclinometer," which measures short distances. It will take a measurement every 0.25 meters. Finally, a "continuous rolling inclinometer" will take continuous measurements as it moves over the pavement.
"The combination of those three devices will give us a true profile," Henry said.
In a part of their experiment that has special interest for FHWA, the professors also plan to compare the measurements they get from the three pieces of equipment to measurements obtained from the Road Surface Analyzer (ROSAN), which is a joint project of TFHRC and Surfan Engineering and Software Inc. of Sumter, S.C. The ROSAN tests were performed by Dr. James Mekemson and Ralph Wigton, on-site contractors at TFHRC.
In just one testing session, the automated and computerized device, which is mounted on a vehicle and does its measuring while the vehicle is moving at normal traffic speeds, will soon be able to gather data on 160 kilometers of pavement. ROSAN specializes in measuring macrotexture - any change in the pavement surface that is greater than 0.5 millimeters and less than 5 millimeters - but it can also measure even smaller and larger surface height changes. That data can be used to help forecast the life of the pavement.
The most sophisticated model of ROSAN, currently under development, combines laser sensors, accelerometers, distance pulsers, bumper-mounting hardware, a vehicle-mounted beam, and a motorized trolley in one neat package. The hardware is controlled by a TFHRC-written, Windows-based program that is very user-friendly.
The ROSAN package is mounted on the front of a vehicle, the engineer or technician controlling it pushes a few command buttons and the vehicle's driver takes off. ROSAN can measure macrotexture, faulting, grooving, rutting, slope, and road profile at speeds of up to 120 kilometers per hour. Because ROSAN itself never touches the road, it stood apart from other equipment evaluated by Wambold and Henry at TFHRC last October.
ROSAN will be on the road with the professors beginning in April 1998 for testing to be conducted in Arizona.
Henry said each testing phase should take about two weeks. Most of the time in the two-year project will be spent analyzing the data from those tests, he said.
Wambold said the event at TFHRC gave the professors a strong start.
"We had a good opportunity there," he said.
Dennis G. Sixbey is the manager of Pavement Surface Analysis (PSA) Laboratory at TFHRC. The PSA Laboratory is part of the Special Projects and Engineering Division. Sixbey is a research materials engineer and has worked in the Office of Engineering Research and Development since 1989. He has a bachelor's degree in civil engineering from the State University of New York at Buffalo. He is a registered professional engineer in Virginia.
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