Letter from R.P Gilliland to Carl Hayden regarding the sale of Bright Angel Trail (Ariz.) and construction of the President's Highway from Maine, AZ, to the Grand Canyon.

The study details the direct and indirect impacts of roads on natural resources, including direct mortality and loss of habitat, physical changes to the topography and hydrology of an area, impacts to habitat, noise, light and other types of pollution, and habitat fragmentation.