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Article Excerpt
America's highways enable people and products to travel to every corner of the country. Along the way, these roads pass through the habitats of many wild-life species. Where roadways cross paths with foraging and migration routes, collisions occur--and in greater numbers than might be readily apparent.
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According to the Federal Highway Administration (FHWA), the number of reported motor vehicle crashes between 1990 and 2004 held relatively steady at slightly more than six million per year. By contrast, the number of reported animal-vehicle collisions (including wildlife and domestic animals) increased by approximately 50 percent over the same period.
FHWA recently completed a study for the U.S. Congress looking at wildlife-vehicle collisions. According to Wildlife-Vehicle Collision Reduction Study: Report to Congress (FHWA-HRT-08-034), an estimated one to two million collisions occur each year between cars and large, wild animals in the United States. This presents a real danger to human safety as well as the viability of some wildlife populations.
Wildlife-vehicle collisions can have a broad range of consequences for both people and animals. The most common results are wildlife mortality, vehicle damage, secondary motor vehicle crashes, and emotional trauma for motorists. A less direct impact is travel delays. Wildlife-vehicle collisions also can require the assistance of law enforcement personnel, emergency services, and road maintenance crews for repairs and carcass removal.
For animals, collisions with vehicles present an immediate danger to their individual survival. In addition, certain threatened and endangered species can face even greater reductions in their numbers, potentially affecting their ability to survive as a population. The FHWA study documents 21 federally listed threatened or endangered animal species in the United States for which road mortality is a threat to survival of the species or population.
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Reducing these collisions continues to pose a challenge for the transportation community. According to the FHWA Report to Congress, "State and local transportation agencies are looking for ways to balance travel needs, human safety, and wildlife conservation."
Highway agencies already are using wildlife crossings, such as overpass and underpass structures, along with installation of fencing to restrict animals to using those structures and avoiding other long segments of roadway. But certain roadway conditions such as steep rocky slopes and deep snowpack are not always conducive to installing and maintaining wildlife crossing structures and fencing. To address the limitations of these traditional approaches, researchers are pushing forward with advances and deployments in three alternative areas: animal-vehicle detection systems, activated warning signs, and electric fencing and mats. Often these technologies can be combined at one location to enhance animal detection, alert drivers, and, most important, reduce collisions.
Animal Detection Systems
Animal detection systems use sensors to detect large animals as they approach the road. The two most common technologies for detecting animals in the roadway environment are area coverage sensors and break-the-beam sensors.
Area coverage sensors detect large animals within the range of the sensor and can be either active or passive. Active coverage systems send a signal over an area and measure its reflection. Microwave radar is the primary technology used for active systems. Passive systems detect animals by only receiving signals. The two most common are passive infrared and video detection. These systems require algorithms that distinguish between moving vehicles with warm engines, moving pockets of hot air, and movements of large animals.
Break-the-beam sensors detect large animals when their bodies block or interrupt a beam of infrared, laser, or microwave radio signals sent between a transmitter and receiver.
The Colorado Department of Transportation (CDOT) is testing another sensor technology, known as intrusion detection, to reduce animal-vehicle collisions on U.S. 160 between Durango and Bayfield, CO. Military installations, prisons, airports, and some private landowners have used this particular technology for perimeter security, but its use in...
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