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February 01, 2001
It happens every year. Just when you think youre safe from winters treacherous roads they begin to reveal Americas "unofficial winter crop": fresh new rash of potholes. As highway engineers try frantically to keep pace with the damage, drivers around U.S. cities spend on average almost $150 each year thanks to poor road conditions.
Part of the problem stems from the difficulty of monitoring roadways. But Kelvin Wang, a civil engineering professor at the University of Arkansas, has developed the worlds first digital solution for recording, storing, and analyzing vast quantities of information about road surfaces.
How do they keep track anyway?
The old system of monitoring roads
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According to Wang, his new system is a high-tech version of an old idea: filming the nations roadways. "State highway agencies around this country have been using video information probably since World War II, so nearly 50 years ago people started using this information," he points out. "In the very early stage, they had been using 16 millimeter or 35 millimeter film, and later on in the 70s they started using videotapes."
The problem with using videotapes is that it creates huge numbers of tapes that engineers then have to sort through and analyze. With almost four million miles of roads in the U.S. in 1997, according to the Bureau of Transportation Statistics, thats a lot of videotape to keep track of. Whats more, its difficult to synchronize the video data with computer engineering programs, and only one person at a time can view a tape. "The most widely used method to survey surface distress of highway pavements—human observation—is extremely labor-intensive, error-prone and hazardous," Wang says.
How does the new system work?
The new system can analyze close-up digital images of roadways, like the cracked pavement at the bottom right of the screen above.
To address these problems, Wang developed a test vehicle that uses digital cameras and laser sensors to record highway surfaces at normal driving speeds. That information can be stored directly on computers which can then analyze and categorize the road surface damage, giving engineers a better overall picture of how the roadways in an area are aging. This system has two advantages: First, since its computer-based, its easily searchable by any number of people; second, the higher resolution of digital cameras allows engineers to get a better look at whats going on.
Right now, theres only one prototype vehicle that was built at a cost of more than $500,000. But Wang hopes that future vehicles wont be so expensive, in part due to the decreasing cost of computer components. Also, he points out that since the system allows highway engineers to keep track of potential problems more efficiently, it will help save tax dollars.
Until more vehicles can be built, Wang and his colleagues have devised a system that can digitize existing video footage so that it can be combined with engineering software. But they expect that digital vans will be a common sight on the nations highways in just a few years.
Why do potholes form?
Potholes are caused by cracks in the road surface that let water get underneath. The cracks get bigger when the water freezes because ice takes up more room than water. Its the same phenomenon that causes a can to explode if its left in the freezer too long. But in the road, the ice melts and leaves a hole, causing the pavement to cave in and form a pothole.