Vision Technologies Automate Urban Inspections

More than 4 million miles (6.5 million km) of roads cross the United States, with millions more in other countries. Proper maintenance is essential to ensure the safety of the users of these roads. Frequent repaving to completely prevent problems is too expensive, but word of mouth, resident complaints, and spot checks are not a dependable basis for planning repair work. As a result, systematic inspection of all roads is necessary-but that's expensive, too. To make things worse, systematic inspection needs to be done on a regular basis with the changes tracked and analyzed over time to predict when road repair will be necessary and to schedule the work in advance. Cash-strapped city and regional governments, therefore, need an inexpensive way to manage ongoing road maintenance and repair.

Fortunately, vision systems are coming to the rescue. City, town, and regional governments use vision systems to help municipalities maintain their share of the world's roadways. Allied Vision Technologies (AVT) is a leading manufacturer of high-performance vision cameras. According to AVT's Web site, vision systems can "collect field data and assess the condition of all roadway and pavement features such as longitudinal cracks, transverse cracks, alligator cracks, edge cracks, potholes, and rutting. Image-based systems offer a less labor-intensive and more reliable solution than traditional manual surveys, and allow the data to be stored for future referencing."

A system developed by AVT and used in the state of Florida incorporates two cameras from AVT and software from NorPix Inc. The cameras, mounted on the roof of a vehicle with one facing forward and one to the rear, capture images of the roadway every 5 to 10 feet (1.5 to 3 meters) as the vehicle drives over it, for a total of up to 180,000 images per day. GPS data is linked to the images to reference them to their actual locations. Images are geometrically flattened to eliminate perspective distortion from the angle of the photograph, superimposed on a map for analysis, and compared with images of the same location from previous years to determine the rate of change. The AVT system still relies on people for the final data interpretation, though its image-processing capability simplifies their task.

Other vision systems can analyze the pavement as well. Pavemetrics Systems of Québec, Canada, offers systems that use lasers and high-speed cameras with custom optics to detect cracks, ruts, and surface deterioration, at speeds of over 60 mph (100 km/hr), day or night, on all types of road surfaces. Pavemetrics systems classify cracks into three categories and evaluate their severity. The systems can also measure and report on the condition of lane markings.

The use of vision systems in pavement inspection is expected to become much more widespread in next few years. However, pavement inspection imposes unique challenges on vision systems. Inspection must take place quickly so that the inspecting vehicle won't obstruct traffic. The system must be able to tell the difference between a crack and other surface imperfections such as oil stains under conditions of low contrast. All in all, vision systems in pavement inspection have a tall order, but filling it saves government agencies a great deal of money by making road repairs at the right time-not too early, not too late-and on a planned rather than an emergency basis.

Vision systems are evolving rapidly. Improvements to the underlying hardware and software technologies, combined with research into the use of those components in a variety of vision-based applications, contribute to better acquisition, storage, and analysis of images.

Discussion Questions
1. What other routine inspections do city, state, and national governments perform? How could vision technologies, combined with knowledge management systems, improve efficiency?

2. How could vision systems, combined with knowledge management systems improve government accountability and help citizens keep track of government performance?

Critical Thinking Questions
1. You work for a city highway department. Your job is to drive over its roads, noting their condition to determine which must be repaired, which must be monitored, and which can be left alone for a while. Your mayor suggests that the city should buy a vision system and asks for your opinion. Options include (a) no new system, (b) a system such as the AVT system mentioned earlier, and (c) at higher cost, a system such as the Pavemetrics system. Write a memo to the mayor making and justifying your recommendation.

2. A van equipped with a pavement inspection system costs about as much as a full-time highway department employee for a year. The highway department employee can use a car that the department already has. In addition, there are ongoing costs for using and maintaining the inspection system. Compare, as best you can from the available information, the costs of a pavement inspection system with its possible benefits.