Under programs administered by the Department of Transportation's (DOT's) Federal Highway Administration (FHWA), certain highway and bridge projects may be eligible to receive federal-aid funding. As a condition of receiving those funds, a project sponsor (e.g., a local or state transportation agency) must meet certain standards and requirements applicable to activities completed at every stage of project development. Although the names of those stages may vary somewhat from state to state, those stages generally include initial project planning, preliminary design/engineering and environmental review, final design and rights-of-way acquisition, construction, and facility operation and maintenance. Each stage of project development is initiated and completed largely at the state or local level, with FHWA having ultimate responsibility for ensuring that individual projects comply with requirements applicable to federal-aid highways. Also, each development stage involves a range of activities that will affect the time it takes to deliver the project. Required elements of the preliminary design and environmental review stage will vary by project, but generally include processes necessary to identify and demonstrate compliance with environmental requirements applicable to that project. When there is debate over the time it takes to complete federally funded highway projects, particularly debate over activities that may expedite or delay project delivery, various elements of the environmental review stage of project development have been the focus of attention. However, whether or the degree to which elements of that process may delay projects is unclear. The two most recent laws authorizing DOT programs included requirements intended to expedite the environmental review process that focused primarily on procedures necessary to demonstrate compliance with the National Environmental Policy Act of 1969 (NEPA, 42 U.S.C. §4321 et seq.). Current legislation to authorize DOT programs in the House and the Senate (the American Energy and Infrastructure Jobs Act of 2012 ( H.R. 7 ) and Moving Ahead for Progress in the 21 st Century (MAP-21; S. 1813 )) also include provisions intended to expedite project delivery that focus primarily on the NEPA process. Despite the focus on the NEPA process, it is unclear whether or how changes to that process would result in faster highway project delivery. Available evidence regarding potential causes of project delays associated with environmental compliance is largely anecdotal and specific to unique, individual projects. Still, that evidence, while limited, points to issues or requirements apart from NEPA as more common causes of project delays. This report identifies issues relevant to the debate over the role of the environmental review process in transportation project delivery. It identifies social and environmental issues that led Congress to enact the range of requirements that now make up the environmental review process, as well as selected requirements applicable to its implementation (particularly NEPA requirements). The report also identifies complexities in tying the environmental review process to federal-aid highway project delivery time. In particular, it identifies issues that make it difficult to determine the time it takes to complete the project development process, in general, or individual stages of development (e.g., activities related explicitly to environmental reviews); or to identify root causes of project delays tied to specific elements of the environmental review process. This report also discusses various approaches identified by transportation stakeholders as those that have expedited the environmental review process and overall project delivery. Information and issues in this report were selected to help Members of Congress and their staff understand the NEPA compliance process as well as additional environmental compliance requirements that may be affected by H.R. 7 and MAP-21. Discussion of specific legislation is provided separately in CRS Report R42445, Surface Transportation Reauthorization Legislation in the 112 th Congress: MAP-21 and H.R. 7, Major Provisions , coordinated by [author name scrubbed]. Activities that may take place during the environmental review process and how that process is implemented will vary from project to project, from state to state. The environmental review process does not involve compliance with a single federal compliance requirement. It involves processes necessary to demonstrate compliance with a potentially wide array of requirements applicable to projects approved under the Federal-aid Highways program. Broadly, for federally funded highway projects, it involves two separate, but related processes—preparing appropriate documentation required under NEPA; and identifying and demonstrating compliance with any additional state, tribal, or federal environmental requirements applicable to that project. For a given project, how NEPA and other environmental compliance requirements must be demonstrated will largely depend on the degree to which the proposed project would have adverse effects on communities, natural or cultural resources (e.g., wetlands, endangered species habitat, historic sites, parks, or recreation areas), or special status land (e.g., farmland, floodplains, or coastal zones). Compliance with those requirements may include obtaining a permit, approval, study, or some level of analysis or consultation from an agency outside DOT. NEPA was intended, in part, to ensure that federal agencies would consider the environmental impacts of an action among other factors (e.g., economic or community benefits) in the federal decision-making process. NEPA has two primary aims—to assure that federal agencies consider the environmental effects of their actions before proceeding with them and to involve the public in the decision-making process. NEPA does not require an agency to elevate environmental concerns above other factors in the overall federal decision-making process. If the adverse environmental effects of a proposed action are adequately identified and evaluated, an agency is not constrained by NEPA from deciding that other project benefits outweigh the environmental costs and moving forward with the action. In contrast, other requirements applicable to federal-aid highways may dictate or somehow affect the outcome of a project decision. For example, other federal laws may require the selected project alternative to be the one with the least impact to a particular resource, prohibit FHWA approval of a project alternative that uses certain resources, require certain mitigation measures to limit a project's impacts, or require that certain activities take place in accordance with certain criteria (e.g., as specified in a permit or approval). Required elements of the environmental review process, particularly compliance with NEPA, will have an effect on project development. For example, before DOT can approve a project and allow final project design, property acquisition, or project construction to proceed, the project sponsor must appropriately document compliance with NEPA and complete any investigation, review, or consultation necessary to demonstrate compliance with other applicable environmental requirements. Further, it is DOT policy to use the NEPA compliance process as a mechanism to balance transportation decision making by taking into account the potential impacts on the human and natural environment and the public's need for safe and efficient transportation. State and local transportation agency officials and other stakeholders with an interest in transportation improvement generally acknowledge that elements of the environmental review process provide important protections to the human, cultural, and natural environment. However, those officials also sometimes argue that completing the process can be difficult and time-consuming. Some have argued, for example, that the time it takes to complete required NEPA documentation and supporting analysis or to obtain required input or approval from outside agencies can delay completion of federally funded transportation projects. It is generally not disputed that the time it takes to complete the environmental review process for federally funded highway projects can take months or even years. What is unclear is the degree to which elements of the environmental review process directly or routinely delay project delivery. Determining the time it takes to complete activities associated with the environmental review process, or delays directly attributable to those activities, is difficult for several reasons including, but not limited to: Limits to available data . There is no centralized source of data regarding highway project delivery. States generally do not track project development time from planning to construction. States generally do not attempt to isolate elements of the environmental review process, which may overlap with preliminary project planning, design, or engineering activities. Further, there is no standard measure for determining when a project or the environmental review process, in particular, is completed "quickly" or would be considered "delayed." The influence of local factors on project delivery. The environmental review process may start, stop, and restart for reasons unrelated to environmental issues. Local and state issues have been shown to have the most significant influence on whether a project moves forward relatively quickly or takes longer than anticipated. Those issues include the project's level of priority among others proposed in the state; changes in funding availability; and local controversy or opposition to the project (which may or may not be connected to environmental issues). The v ariation in project type and complexity. The wide range of projects approved under programs administered by FHWA (e.g., bridge repair versus major new highway construction) do not easily allow an "apples to apples" comparison of the time it takes to complete the environmental review process or factors that may delay it. Anecdotal evidence regarding projects identified as "delayed" have involved multiple, complex causes of delay (including local issues) unique to that project, not a single cause that may be commonly applicable to other projects. Variation among state requirements and implementation processes . The effect of requirements under federal law may be difficult to isolate since local, state, or tribal requirements and procedures will also affect how environmental compliance requirements are implemented. State DOTs implement their project delivery process differently, depending on factors specific to their state and its needs. For example, some states may implement unique design and contracting processes that expedite project delivery that other states do not. Time " saved " cannot be gauged. Depending on the scope and complexity of the project, more time spent addressing environmental issues in the project planning and preliminary design stage may result in faster completion of final design and project construction (when delays may require actions that take more time and money to address). Time may also be saved when adverse project impacts that could lead to local opposition to the project are identified and addressed during the early stages of project development. Transportation agency officials and project sponsors have broadly identified environmental compliance requirements as a common source of frustration in completing the project development process. However, limits to and contradiction in available data make it difficult to clearly identify specific causes of delay that are directly and routinely attributable to specific elements of environmental compliance.