a railway line, business park, roadway, and sports complex . Monitoring is currently underway to examine the effectiveness of this innovative project combining wildlife protection with urban development. The oldest wildlife passage is Zeist West - A 28, opened in 1988. Slaty Creek Wildlife Underpass, Calder Freeway, Black Forest, Australia Another case study of the effectiveness of wildlife crossings comes from an underpass built to minimize the ecological effect of the Calder Freeway as it travels through the Black Forest in Victoria, Australia. In 1997, the Victorian Government Roads Corporation built Slaty Creek wildlife underpass at a cost of $3 million . Scientists used 14 different techniques to monitor the underpass for 12 months in order to determine the abundance and diversity of species using the underpass . During the 12-month period, 79 species of fauna were detected in the underpass (compared with 116 species detected in the surrounding forest) including amphibians, bats, birds, koalas, wombats, gliders, reptiles, and kangaroos . The results indicate that the underpass could be useful to a wide array of species but the authors suggest that Slaty Creek could be improved by enhanced design and maintenance of fencing to minimise road kill along the Calder Freeway and by attempting to exclude introduced predators such as cats and foxes from the area. I-70 Vail Pass, Colorado In 2005, area environmental groups floated the idea of a wildlife overpass west of Vail Pass. In 2010, ARC Solutions – an interdisciplinary partnership – initiated the International Wildlife Crossing Infrastructure Design Competition for a wildlife crossing over Interstate 70 in the high country west of Denver, Colorado; designers had to account for challenges unique to the area, including snow and severe weather, high elevation and steep grades, a six-lane roadway, a bike path, and high traffic volumes, as well as multiple species of wildlife, including lynx. After receiving 36 submissions from nine countries, a jury of international experts in landscape architecture, engineering, architecture, ecology and transportation selected five finalists in November 2010 to further develop their conceptual designs for a wildlife crossing structure. In January 2011, the team led by HNTB with Michael Van Valkenburgh & Associates (New York) were selected as the winners. The design features a single 100 m (328 ft) concrete span across the highway that is planted with a variety of vegetation types, including a pine-tree forest and meadow grasses, to attract different species to