 The construction of the freeway over Vail Pass is also listed as an engineering marvel . One of the challenges of this portion is the management of the wildlife that roams this area . Several parts of the approach to the pass feature large fences that prevent wildlife from crossing the freeway and direct the animals to one of several underpasses . At least one underpass is located along a natural migratory path and has been landscaped to encourage deer to cross . 
