Page:America's Highways 1776–1976.djvu/402

 Highway beautification was also given a boost by the National Recovery Act of 1933, which included among its objectives the landscaping, with Public Works funds, of a moderate mileage of main roadsides. The rules and regulations governing the use of these funds required that at least one-half of 1 percent of each State’s apportionment should be devoted to this type of improvement. Thus, a total of approximately $2 million was set aside for pioneering work which had for its ideal the conversion of unsightly roadsides into attractive areas bordering roadways made safe for those traveling upon them.

The Federal-Aid Highway Act of 1940 was a further landmark in legislation in support of better looking and safer roadsides. Section 11 of this act authorized the use of Federal funds for “. . . such roadside and landscape development, including such sanitary and other facilities as may be deemed reasonably necessary to provide for the suitable accommodation of the public. . . and. . . likewise. . . the purchase of. . . adjacent strips of land of limited width and primary importance for the preservation of the natural beauty through which highways are constructed. . .” The Highway Beautification Act of 1965 further liberalized the use of Federal funds for roadside improvements, such as control of outdoor advertising and the control of roadside junkyards.

Returning for a moment to the Mount Vernon Memorial Highway, one reason for its attractive appearance was its gentle sinuous alinement; there were no long tangents and no abrupt, short radius curves. Yet, the highway formed a reasonably direct route between termini. It was the antithesis of the type of alinement that was evolving for conventional two-lane highways which, by their very nature, necessitated that vehicles encroach upon the opposing lane of traffic in order to overtake and pass slower vehicles. Straight alinement with good sight distances was thus a requisite of a good, safe two-lane road.

By way of contrast, the Mount Vernon highway was a four-lane highway on which faster cars could overtake and pass slower ones without having to encroach on the lane for oncoming traffic. Thus, passing sight distance was not important. The curves on the Mount Vernon highway were of longer radius than those generally used on two-lane roads, and there was no necessity for the motorist to vary his speed in traversing the entire length of the route. One curve has been said to be over 2 miles long. All curves were provided with spiral transitions.

This departure from conventional curve design was achieved through the use of a flexible spline of the type used in ship design, and this was one of the early applications of the method. A prerequisite of this method of location and design is a topographic map of fairly large scale and of sufficient width to include all alternative locations for the selected routes. As has been mentioned, aerial photographs were very helpful in this regard, and this project was one of the first to use this technique. The methods for determining elevations from the two-dimensional photographs were crude and lacked precision, and there were other problems to be overcome, but the benefits of seeing the vegetation, the drainage courses, the configurations of the ground, and the land uses as they appeared in nature were tremendous.

Rapid strides were to be made in photographic techniques and in the development of equipment for interpreting and photogrammetrically plotting topography by use of contours on topographic maps entirely adequate for precise highway location and design. Improvements were to continue. Looking ahead, the Federal-Aid Highway Act of 1956 authorized “the use of photogrammetric methods in mapping, and the utilization of commercial enterprise for such services.” By 1960, the accuracy and practicality of aerial survey methods were so well recognized that contractors were willing to accept payment for earthwork computed on the basis of cross sections measured photogrammetrically using aerial photographs taken before and after the construction work was performed.

An arterial highway of the 1940’s with uncontrolled access. An early form of channelisation helped traffic movements, but the danger from cars backing out onto the highway still remained.

At the same time that new techniques were being discovered or improved, new concepts and principles were being recognized. One of these, soon to be exploited, was the principle of control of access. It would be difficult to say when the first public highway was planned with the express intent of excluding abutting property owners from access to the road for the purpose of protecting and preserving the operational character of the highway. One of the earliest examples of a controlled access highway is the Bronx River Parkway in New York. It was designed about 1914 and completed approximately 10 years later. It has been said that this project was conceived as an attempt to protect the historical old Bronx River, but as studies developed, it was found that protection was feasible only if the land on both sides were purchased in fee. Once the land was purchased, it appeared desirable to use it for park purposes and then for a parkway to relieve the congestion on the heavily traveled north-south streets in the area. Regardless of whether this controlled access parkway came into being by accident or whether by intent, it stood for half a century as a lasting proof of the value of controlled access. Whereas other roads of much higher standard built decades later have since become obsolete because of roadside interference, the original Bronx River Parkway retained all of its beauty and 396