AASHTO PH 12:2016 ASSESSING INDIRECT EFFECTS AND CUMUL ATIVE IMPACTS UNDER NEPA.
Potential for Increased Mobility and/or Accessibility. The potential for travel time savings (shorter, faster trips) and/or increased accessibility is a key determinant of a project’s potential to induce growth. If a project simply involves the repair or replacement of an existing structure, without any increase in capacity or adding a new access point, it generally will have little or no ability to induce growth. On the other hand, if a project substantially reduces travel times or creates a new access point on a transportation facility, the project may have the potential to induce growth. Traffic modeling provides a quantitative basis for assessing potential travel time savings. Early in a study, when forecasts are not yet available or are highly preliminary, it may be possible to assess travel time savings qualitatively based on the nature of the improvement being proposed.
Growth Trends and Projections. The basis for assessing induced growth is an understanding of the growth trends that would occur in the absence of the project. Growth trends can be described in many ways, including data on population and employment, housing construction, commercial and industrial development, conversion of undeveloped land, and other factors. While the specific data used will vary from project to project, it is always important to describe existing growth trends in some manner as a frame of reference for assessing a project’s potential to Induce different or greater growth than would have otherwise occurred. Keep in mind that a “No Action” growth projection should reflect growth as it would be expected to occur without the proposed project. Developing such a projection involves subjectivity and judgment; the assumptions and methodology used in developing such projections should be carefully documented.
Land Use Plans. Land use plans and other related plans, such as economic development plans, provide a basis for distinguishing between planned and unplanned growth. There are times when development is planned prior to development of the roadway network. The fact that growth has been planned doesn’t necessarily mean it was not induced by a project; a project can be the necessary condition for planned growth, such as when a new interchange is constructed to serve a master-planned development. Nonetheless, the distinction between planned and unplanned growth is often an important consideration in project decision-making, because planned growth is generally considered preferable to unplanned growth. In addition, the distinction between planned and unplanned growth may be relevant in determining the level of detail required in the indirect impacts analysis. Growth that is unplanned, or that conflicts directly with land use plans, may warrant a more detailed discussion in the indirect effects analysis. Under the CEQ regulations, any inconsistencies with land use plans must be specifically identified in an EIS.9
Constraints on Growth Potential. Even in situations where a transportation project increases mobility and accessibility, other factors may limit the potential for induced growth. Constraints on growth include factors such as lack of demand, lack of available land, lack of water and sewer infrastructure, land use controls, regulatory constraints, and public opposition to development. These types of factors also play an important role in assessing a project’s potential to cause induced growth, and are particularly important in assessing the degree to which increased accessibility and mobility will translate into increased growth.
Presence of Protected/Sensitive Resources. If a project has the potential to induce growth, it is necessary to consider whether the induced growth is likely to impact protected, impaired, threatened, or otherwise sensitive resources—for example, wetlands, forests, farmland, or wildlife habitat. As a basis for making this determination, an indirect effects analysis typically includes an inventory of the noteworthy natural and human resources in the area where induced growth could occur.AASHTO PH 12 pdf download.