Three factors -- project funding sources and project characteristics, and whether a state allows the adoption of federal review documents generally determine whether a highway project needs a federal environmental review under the National Environmental Policy Act (NEPA) or a state environmental review under state law, or both. This book focuses on environmental reviews of highway projects in states with SEPAs and addresses factors determining whether federal or state environmental reviews are required; how state and federal review requirements compare; and the extent of any duplication in federal and state reviews, including frequency and cost. This book also discusses the role of the environmental review process in federally funded highway projects.