Built in the 1990’s, Vasco Road in eastern Contra Costa County bisects a wide expanse of open rolling hills dominated by annual grassland, and includes numerous wildlife undercrossings of various sizes and configurations that were built either during initial construction or during later highway improvement projects. This study by Nomad Ecology used camera stations to monitor wildlife use of undercrossings along an approximately 4-mile stretch of Vasco Road that passes through Preserve land owned by the East Bay Regional Park District and managed under conservation easement by the East Contra Costa County Habitat Conservancy. Over three seasons from 2023 to 2025 this study has documented thousands of successful wildlife crossing events by various mammal species such as coyotes, bobcats, American badgers, and cottontail rabbits, including through undercrossings that were relatively long and/or narrow. Even undercrossings with angles where one end is not visible from the other were used, and sometimes with great frequency. Wildlife showed differential use of the crossings across the landscape, with some species concentrating their activity at certain undercrossings. In aggregate, the undercrossings monitored in 2023 were used by at least one wildlife species on an almost daily basis, with 0.908 crossings per trap-night, and even more frequently for those monitored in 2024, with 1.845 crossings per trap-night. Analysis of 2025 data is currently underway. Maintenance of the undercrossings, such as removal of live and dead vegetation, debris, and accumulations of roadside trash has been crucial to ensuring that they remain open and available for use by wildlife.