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 led, in many cases to economic surveys and studies designed to ascertain what the facts actually were. Typically these studies showed mixed results; some businesses suffered from the diversion of through traffic, some benefitted, and some were little affected.

This issue, which first surfaced in the years just prior to World War II, reached a peak during the 1950’s, and then gradually disappeared. Traffic volumes became so large that it was very apparent that they could no longer be carried on existing urban arteries.

A number of other developments, starting in the mid-1950’s, served to focus attention on the effects that highways might have on adjacent areas. Prominent among these was the increasing reliance upon freeways for the safe and effiicentefficient [sic] handling of major traffic flows. In developed areas, controlled access and other characteristics of freeways were extremely difficult, to achieve by upgrading existing highways. New freeways, therefore, were nearly always constructed along new alinements, and thus, their impacts upon adjacent areas were imposed suddenly and without time for adjustment.

Many of the new freeways in the Interstate and other programs were located in or near the large urban areas where traffic demand was the heaviest. These were also the areas where the possibilities for displacement from homes and businesses were the greatest and where such adverse effects as noise and air pollution were most keenly felt.

An awareness of the hazards caused by vehicular emissions and poor air quality, in general, also basically developed only in the last 10 to 15 years. The density of smog over a number of large urban areas warning of future dangers dramatically brought a heightened environmental consciousness to the people at large and increased the demands for corrective action.

Increased awareness of the environmental effects of highways has led to a variety of responses by Congress, by the FHWA, and in some instances by other agenicesagencies [sic] or organizations. Some of the congressional actions have been additions or amendments to basic highway legislation, but others, such as the National Environmental Policy Act of 1969 (NEPA), apply to a wide range of Federal programs, including highways.

Largely as a result of the bypass controversy, Congress, in the 1950 Federal-Aid Highway Act, required State highway departments to hold public hearings for all projects bypassing cities or towns. In 1956 this requirement was enlarged by requiring public hearings (or the opportunity for hearings afforded) for routes going through cities or towns as well as those bypassing cities or towns. Two years later, in the Federal-Aid Highway Act of 1958, the public hearing requirement was applied to Interstate projects. In effect, public hearings are now necessary for all major projects and for projects of any size which have generated public interest or controversy.

In 1969 the FHWA released new detailed provisions requiring that two hearings (or the opportunity for them) be held for each important project, one at the location stage and the other at the design stage. Later, in 1974, however, this two-hearing requirement was modified. New regulations permit a State to omit one of the hearings providing its Action Plan spells out acceptable alternative procedures for accomplishing the same objectives.

Erosion control during construction is aided by these silt fence installations along the Natchez Trace Parkway. Other methods used are temporary riprap at culvert inlets, plastic sheeting to carry cross drainage, and brush barriers in conjunction with filter fabric on embankments. 371