An essential element of NEPA decisionmaking for tranportaion projects is the consideration and analysis of the potential environmental impacts or effects (ecological, aesthetic, historic, cultural, economic, social, or health) of our projects and actions. This includes not only the direct impacts, but also indirect effects (sometimes called secondary effects) and cumulative impacts. Keep in mind that these impacts are different and distinct from one another and are treated differently in environmental analyses. The CEQ Regulations defines direct and indirect effects and cumulative impacts at 1508.7 and 1508.8:

Cumulative impact - 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.

Direct effects - are caused by the action and occur at the same time and place.

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.