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Roads bisecting animal habitats have long caused fatal collisions and blocked migration routes. In response, engineers have built wildlife crossings: vegetated overpasses and tunnels that let animals traverse highways safely. Banff National Park's system, one of the earliest large-scale examples, uses fencing to funnel elk, wolves, and bears toward dedicated overpasses rather than the road itself. Studies tracking the structures over two decades found that collisions with large mammals dropped by more than eighty percent along fenced sections. Critics initially doubted animals would use human-built structures, but camera traps have recorded generations of the same species crossing repeatedly, suggesting the behavior becomes learned and passed on rather than merely tolerated.