Effective wildlife fencing and crossing structures can significantly reduce many harmful impacts of roads on wildlife populations. Yet currently there is limited knowledge of how to incorporate these structures for most wildlife species into transportation projects. For example, studies have shown that wildlife use crossing structures, but level of use varies between species of wildlife, locations and landscapes, and the reasons why are unclear. Recommended minimum dimensions have been suggested for some ungulate species, but the needs of wide-ranging species are vague at best. Human activity can significantly influence how wildlife use structures. Others have inferred that crossing structure location, particularly in relation to habitat quality, might be the most important design feature of successful wildlife crossing structure applications. In spite of these valuable kernels of information, gaping holes in our knowledge of functional wildlife passage systems remain. Practically all of the performance evaluations to date have focused on single-species and limited attention has been paid to multiple-species relationships. After nearly a decade of increased activity building crossing structures, engineers and land managers still lack guiding principles as a large void exists in devising functional designs based on criteria that are relevant to real management decisions. It is timely to conduct a critical assessment of the current status of these mitigation measures and experience in an adaptive management process. A growing body of literature and information base has resulted from nearly a decade or more of increased implementation of wildlife crossing systems in North America. This project serves as the first attempt to gather, review and critically analyze current information on ecological criteria and design attributes of wildlife crossing structure planning and performance. We will obtain data on specific passage use from reports in journals, conference proceedings, in-house technical reports and informal contacts with colleagues.