69 between Sudbury and Killarney, as part of the route's ongoing freeway conversion. Costs and benefits The benefits derived from constructing wildlife crossings to extend wildlife migration corridors over and under major roads appear to outweigh the costs of construction and maintenance. One study estimates that adding wildlife crossings to a road project is a 7–8% increase in the total cost of the project . Theoretically, the monetary costs associated with constructing and maintaining wildlife crossings in ecologically important areas are trumped by the benefits associated with protecting wildlife populations, reducing property damage to vehicles, and saving the lives of drivers and passengers by reducing the number of collisions caused by wildlife. A study completed for the Virginia Department of Transportation estimated that underpasses for wildlife become cost effective, in terms of property damage, when they prevent between 2.6 and 9.2 deer-vehicle collisions per year, depending on the cost of the underpass. Approximately 300 deer crossed through the underpasses in the year the study took place . Effectiveness A number of studies have been conducted to determine the effectiveness of wildlife corridors at providing habitat connectivity (by providing viable migration corridors) and reducing wildlife-vehicle collisions. The effectiveness of these structures appears to be highly site-specific (due to differences in location, structure, species, habitat, etc.) but crossings have been beneficial to a number of species in a variety of locations. Examples Banff National Park Banff National Park offers one of the best opportunities to study the effectiveness of wildlife crossings because the park contains a wide variety of species and is bisected by the Trans-Canada Highway (TCH), a large commercial road. To reduce the effects of the four-lane TCH, 24 wildlife crossings (22 underpasses and two overpasses) were built to ensure habitat connectivity and protect motorists . In 1996, Parks Canada developed a contract with university researchers to assess the effectiveness of the crossings. The past decade has produced a number of publications that analyze the crossings' effect on various species and overall wildlife mortality (see , , and ). Using a variety of techniques to monitor the crossings over the last 25 years, scientists report that 10 species of large mammals (including deer, elk, black bear, grizzly bear, mountain lion, wolf, moose, and coyote) have used the 24 crossings in Banff a total of 84,000 times as of January 2007 . The research also identified a "learning curve" such that