Planning for wildlife crossings is a critical activity because: 1) location can determine utilization by individual species and 2) once wildlife crossings are built, they are unlikely to be re-located. Despite how critical this aspect of wildlife crossing siting is, there is little guidance for how to scientifically carry out this step. To help develop the scientific basis for this type of conservation action, we developed a spatially-explicit decision-support system (SEDS) that combined various datasets of wildlife occurrence and habitat suitability models. SEDS was based on a series of steps: 1) objective setting by an organization planning wildlife crossings across State route 152 (SR152), the Santa Clara Valley Habitat Agency, 2) collection of data and models describing potential or actual wildlife occurrence; and 3) development of alternative models incorporating habitat, ownership, wildlife occurrence, constructability, and wildlife use of existing structures. These alternatives informed different ways of making crossing decisions, including under- versus over-crossings, duplication of crossings, and inclusion of single or multiple focal species. The SEDS for SR152 resulted in 4 candidate sites for under- or over-crossings which have been advanced to engineering design and environmental permitting. The approach is currently being used for similar wildlife crossing planning for 6 other highways.