Integrating environmental considerations into transportation planning, design, construction, maintenance, and operations is widely recognized as a complex and challenging undertaking. Since the passage of the National Environmental Policy (NEPA) and other environmental laws in the early 1970’s, transportation agencies have been developing and using a wide variety of environmental management approaches to meet a vast array of environmental goals and requirements. These environmental management approaches have largely involved assessing, avoiding, minimizing, and mitigating the potential environmental effects of proposed transportation improvement projects on a project-by-project basis during the design and construction phases of managing the transportation system.