All phases of road developmentâ€"from construction and use by vehicles to maintenanceâ€"affect physical and chemical soil conditions, water flow, and air and water quality, as well as plants and animals. Roads and traffic can alter wildlife habitat, cause vehicle-related mortality, impede animal migration, and disperse nonnative pest species of plants and animals. Integrating environmental considerations into all phases of transportation is an important, evolving process. The increasing awareness of environmental issues has made road development more complex and controversial. Over the past two decades, the Federal Highway Administration and state transportation agencies have increasingly recognized the importance of the effects of transportation on the natural environment. This report provides guidance on ways to reconcile the different goals of road development and environmental conservation. It identifies the ecological effects of roads that can be evaluated in the planning, design, construction, and maintenance of roads and offers several recommendations to help better understand and manage ecological impacts of paved roads.

This report describes the transportation planning process and discusses where and how environmental factors can be addressed effectively at the state and metropolitan levels. This report should be especially useful to federal, state department of transportation (DOT), metropolitan planning organization (MPO), and local transportation planners, as well as other practitioners concerned with addressing environmental factors within transportation systems planning, priority programming, and project development planning leading to implementation. The research focused on environmental issues within the long-range transportation planning processes of state DOTs and MPOs and included the following: (1) a comprehensive review of recent literature; (2) a survey of approaches employed by state DOTs, MPOs, and environmental regulatory agencies; (3) a review of federal regulations and guidance on environmental factors; and (4) case studies to synthesize current practice in environmental planning.