Visual resource is a collective term that describes the natural landforms, vegetation, water features, and human modifications that give the landscape within a specific area its visual aesthetic quality. A "visual impact" describes the change in visual resources brought about by a project and the public's sensitivity to that change.
FHWA requires that transportation projects consider both positive and negative impacts to visual resources, that they be adequately assessed, and that mitigation measures be implemented to reduce potential adverse effects. More detail about visual impact assessment can be found in FHWA’s Visual Impact Assessment for Highway Projects.
The National Historic Preservation Act of 1966 directs all federal agencies to account for the effects of a proposed project on historic resources; this includes, "the introduction of visual ... elements that are out of character with the property or alter its setting." In addition, Section 4(f) of the Department of Transportation Act advocates for the protection of the natural beauty of the countryside, public parks, recreational lands, wildlife and waterfowl refuges, and historic sites.
Public involvement during planning and design is beneficial in identifying potential actions to mitigate adverse visual impacts.
While conducting an assessment of the impacts to visual resources, questions are addressed such as:
Will the project result in a noticeable change in the physical and cultural characteristics of the surrounding environment?
How sensitive are potential viewers likely to be with visible changes?
Is the proposed project consistent with applicable laws, ordinances, regulations, and policies?
Other visual impact assessment methods for evaluating the scenic attributes of landscapes are the Landscape Aesthetics: A Handbook for Scenery Management prepared by the US Forest Service in 1995. The U.S. Bureau of Land Management uses a method called Visual Resources Management. These assessment methods may be referred to for planning purposes or for assessing the impacts of proposed transportation project.