The Federal Highway Administration and other federal agencies’ responsibility to address and consider direct, indirect, and cumulative impacts in the National Environmental Policy Act (NEPA) process was established in the Council on Environmental Quality (CEQ) Regulations for Implementing the Procedural Provisions of the National Environmental Policy Act (40 CFR §§1500-1508).
The CEQ regulations define the impacts and effects that must be addressed and considered by federal agencies in satisfying the requirements of the NEPA process. Direct, indirect and cumulative impacts can be defined as follows:
- Direct effects are caused by the action and occur at the same time and place. (40 CFR § 1508.8)
- Indirect effects are caused by the action and are later in time or farther removed in distance, but are still reasonably foreseeable. Indirect effects may include growth inducing effects and other effects related to induced changes in the pattern of land use, population density or growth rate, and related effects on air and water and other natural systems, including ecosystems. (40 CFR § 1508.8) Indirect effects and secondary effects are used interchangeably by FHWA.
- Cumulative impact is the impact on the environment, which results from the incremental impact of the action when added to other past, present, and reasonably foreseeable future actions regardless of what agency (Federal or non-Federal) or person undertakes such other actions. Cumulative impacts can result from individually minor but collectively significant actions taking place over a period of time. (40 CFR § 1508.7)
According to FHWA guidance, the determination or estimation of future impacts is essential to both indirect and cumulative impact analysis. However, the focus must be on reasonably foreseeable actions, those that are likely to occur or probable, rather than those that are merely possible.
For additional information on indirect/secondary and cumulative impacts for transportation projects, please see the question-and-answer guidance document, FHWA Interim Guidance: Indirect and Cumulative Impacts in NEPA [DOC 186kb].