As long linear features on the landscape, railways, roads and highways have impacts on wildlife and wildlife habitat that are disproportionate to the area of land that they occupy. In addition to impacts on habitat, highways and railways are sources of road mortality that threaten wildlife populations. Indirect effects on wildlife include reduced access to habitat due to road avoidance and human exploitation. Transportation infrastructure also undermines ecological processes through the fragmentation of wildlife populations, restriction of wildlife movements, and the disruption of gene flow and metapopulation dynamics. A variety of techniques have been used to mitigate the impacts of transportation systems on wildlife movements with mixed success. To make progress on these issues wildlife biologists must: 1) recognize the potential long-term effects of highways and railways on wildlife populations and advocate more strongly for appropriate mitigation measures, 2) document the impacts of transportation infrastructure on wildlife populations, 3) conduct landscape analyses to identify “connectivity zones” and use these analyses to engage transportation planners earlier in the planning process, 4) enlist transportation engineers to help solve technical problems, and 5) design and conduct good monitoring studies to effectively evaluate various mitigation techniques.