Abstract:Advance mitigation is a process through which the environmental impacts and required mitigation are assessed for one or more transportation projects early in project planning and development. The approach enables mitigation to be planned, commenced, and completed earlier; applies regionally or programmatically across multiple projects; and takes ecosystem- and landscape-level concerns into account. Although there have been efforts to develop programmatic mitigation initiatives and funding to support them, there is little documentation of their establishment, operation, or accomplishments. A study documents and analyzes 10 prominent California experiences with advance mitigation undertaken by the state department of transportation in coordination with regional councils, local governments and transportation agencies, and environmental groups. Each effort is profiled, including the origin of the mitigation effort; its location, scale, and cost; its specific connection to transportation projects; funding, revenue sources, or financial options used to support it; key institutional partners; and lessons learned from the experience. California’s initiatives offer some lessons: external conservation planning efforts can play a significant role in creating both momentum and structure for comprehensive mitigation planning; transportation-related advance mitigation is necessarily a highly interdependent undertaking, involving not only the state department of transportation and other transportation project sponsors but also federal and state natural resource agencies as well as local environmental groups; and the long-time horizons of advance mitigation planning and the complex nature of infrastructure development bring unavoidable uncertainty to such efforts and demand flexibility from mitigation partners in the process.