Digital Highways Help Engineers Monitor Wear And Tear

Wang has designed and implemented the world's first fully digital highway data system, which uses digital cameras to record highway surfaces in real time and store the information directly on computer drives. This innovation is a major step toward the first fully automated system.

"Traditional systems are limited by accessibility, search capability of the image library, and synchronizing video data with traditional engineering data," explained Wang. "More importantly, there are situations in which multiple users need to examine the video footage at the same time. This capability cannot be provided by current systems."

With Wang's system, high-definition images of pavement surfaces are directly captured, archived, and analyzed by computers. By applying image-processing techniques to these digital images, engineers can easily identify distresses in the roadway and determine the exact scope of the problem. Distress objects such as cracks and holes can then be classified according to length, width, orientation or other predefined categories.

"The most widely used method to survey surface distress of highway pavements -- human observation -- is extremely labor-intensive, error-prone, and hazardous," Wang explained. "An ideal automated system should find all types of cracking and any other surface distress of any size, at any collection speed and under any weather conditions."

Implementation costs for a fully automated system remain a concern. Although equipment and labor cost for the prototype exceeded $500,000, Wang is quick to point out that subsequent vehicles will be much cheaper and more accurate.

"The cost of computer equipment has dropped dramatically in the past years," he explained. "At the same time, the quality and performance of the available equipment has improved."

However, fully digital systems are still a long way off for most states. To compensate for the inefficiencies of the present system, Wang and his associates have devised a distributed multimedia-based highway information system (MMHIS) that can digitize analog video material and combine it with engineering data.

Most state highway departments usually attempt to examine every mile of highway each year to determine conditions and maintenance needs. With the present system, most states require a specially equipped van to drive over every mile of highway. Cameras in the van videotape the road surface, and the videotapes are stored on shelves in rooms designated for that purpose. To make a decision about a particular road segment, an engineer must find the appropriate tape, find the appropriate segment on the tape and then go to another library to obtain engineering data on that segment.

"This is an extremely cumbersome and time-consuming process," said Wang. "And it goes on in highway departments all across the United States."

MMHIS uses video compression, a video server, a high-speed network and a data-synchronization algorithm to dynamically link video and engineering data. This material can then be readily accessed from a computer on the engineer's desk or shared among multiple users at the same time.

Not only does this system allow highway departments to use the analog equipment they already own, but it also enhances its usefulness. Highway professionals in different parts of the state can access the same information at the same time, which is impossible with the analog tape system. This reduces access problems and facilitates decision-making.

Arkansas is the first state to install the MMHIS system, which was developed through grants from the Arkansas Highway Transportation Department and the Mack Blackwell Rural Transportation Center at the University of Arkansas. Following initial testing, the system is being enhanced to provide additional features.

Implementation of MMHIS allows highway departments to approach a fully automated system gradually. By first combining database innovations with digitized video, engineers can achieve greater efficiencies in analyzing highway surfaces and making maintenance decisions. As funds become available, analog video equipment can be replaced with digital imaging equipment to obtain greater accuracy in assessing the condition of highway pavements.