Bridges and Beautification

ARIZONA HIGHWAYS

Low as safety will permit, in order that as much as possible of the stream is visible to the traveler. From the standpoint of light and cleanliness, open rails are advisable, if well designed and of sufficient mass to lend a sense of security. Grills and wide open rails of this type, unless surmounted by a substantial top rail, do not give that sense of security, even though well designed for strength and durability. An occasional break in the line and interruption of the view with a small mass is not considered objectionable. Many posts, however, give an unpleasant flickering of light and shadow, when observed from a fast moving vehicle. If we recall the bridges of a few years back we will see: First, the light structures, built mostly by the counties. For sake of economy these structures had small, flimsy rails of pipe or angles usually in two parallel lines, the top rail offering little or no protection except to the horse drawn vehicle and pedestrian; certainly none to the modern, highspeed traffic, and we find that on the few of these structures that still exist, the rails are badly damaged or torn away.

Following this type and along with the more extensive use of concrete came the solid panel rails, which, although offering ample protection, were usually of such great height as to completely obscure the view and give the traveler a sense of driving through a deep trough with nothing to see except the blank wall.

On account of span length and low clearances, it is not always possible to keep the main superstructure below the deck. Such a structure is an unfortunate occurrence from a landscape standpoint.

A more difficult problem presents itself in attempting to blend the bridge with the surroundings. A structure such as just mentioned, with steel trusses or other work above the deck, is usually the worst offender in this respect, but again an unfortunate occurrence. This phase of the problem, then, is to make the span as unobtrusive as possible.

Rugged deposits, whereas man made convery similar to our concrete, it is in ruged deposits, whereas man made concrete carries with it the stiff lines required by strength and economy, and steel is entirely a product of man's handiwork.

Recent developments in flame cutting of structural steel and improved methods of electric welding, have greatly improved the architectural value of this very dependable material. The shaping of plates to curves and rounding of sharp corners can now be accomplished with great speed and economy. It is only within the past few years that flame cutting and arc welding have been permitted, and these two methods of working steel have already made great strides in the moulding of more pleasing lines in steel structures.

Plain surfaces with softening curves are usually more fitting, such as are to be found in arch construction and in the development of the more recent rigid frame designs. Even with the advantages offered by these types, the straight lines necessary for strength and economy do not successfully blend with nature.

Finding that we cannot hide our structures in nature's cloak, is it not better, therefore, to create a pleasing effect

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On the opposite page are some examples of Arizona bridge architecture. 1.-New steel span on U. S. Highway 89 between Lee's Ferry and House Rock Valley. 2. New arch bridge at Lowell on U. S. Highway 80, photo by John W. Ball of Bisbee. 3.Bridge 12½ miles south of McNary on U. S. 60, temporary. 4. Crossing Canado del Oro on State Highway 84. 5. Cienega bridge on U. S. Highway 80. 6.Paralle! highway and railway bridges on U. S. 80 at Yuma. 7. Span across the Gila River on U. S. Highway 80, near Gillespie Dam. 8.On U. S. 80, the Gila River bridge at Florence. 9. U. S. Highway 66, the steel bridge crossing the Colorado River at Topock.