Professor creates system to survey pavement cracks
FAYETTEVILLE, Ark. -- At 60 mph, the surface of a highway is only a blur to the human eye, but not to the Digital Highway Data Vehicle.
Until recently, finding every crack in the pavement has required someone to walk slowly alongside the highway, stopping to note the extent of the flaw and its position.
That can be dangerous, with tractor-trailers roaring by just feet away, and costly to pay someone with technical expertise for days and weeks of walking, note-taking and diagram-drawing. The results from different inspectors weren't consistent either.
Kelvin Wang, a civil engineering professor at the University of Arkansas, came up with the DHDV as a solution.
"In pavement engineering, you really need to find out where the cracks are," Wang said.
His digital data gatherer uses a framework mounted behind a minivan that holds four strobe lights pointed at the pavement. A digital camera between the lights snaps 12 frames a second and transmits the image to a pair of computers inside the van. Precise locations for every image are determined using the global positioning satellite.
Two computer monitors in the van allow technicians to watch what the camera is seeing as it snaps the pictures. They then plug the data into three different database programs for evaluating highway problems.
The strobes are timed to flash in synch with the opening of the camera's shutter.
Wang realized the need for the DHDV when he worked as a junior engineer for the Arizona Department of Transportation in the late 1980s and early 1990s, while he was completing work on his doctorate in civil engineering at Arizona State University.
"I saw the issues, the problems, the difficulties that people were facing" in planning and budgeting for highway repairs, he said. Roads and highways represent this nation's largest public investment, Wang said, "but there was no good way to manage" that investment, because manageable data were unavailable.
One or two other systems are available that take pictures of road cracks at highway speeds, Wang said, "but they can't do the data analysis, except very slowly."
That's what makes the DHDV a breakthrough: its ability to analyze the data just as quickly as it is acquired, at highway speed. What Wang calls three "distress protocols" -- systems of classifying highway cracks -- were incorporated into the programming of the system.
The DHDV was developed with some funding from the federal Transportation Department's Mack-Blackwell Transportation Center at the University of Arkansas, as well as grants from the Arkansas Highway and Transportation Department.
Kent Hansen, director of engineering with the National Asphalt Pavement Association in Washington, said the DHDV would be valuable to highway-pavement managers because it's safer, faster and more consistent.
The system costs $300,000 to $500,000, depending on its configuration. Wang hopes it will gain nationwide acceptance, and has formed a company, WayLink Systems Corp., to market the technology. A company based in Austin, Texas, Fugro-BRE, is marketing the system along with WayLink.