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traffic; the latter may be determined with regard solely to the navigation interests, giving due consideration to the cost and the appearance of the resulting bridges, as discussed below.

The plan upon which interest is now most centered is that officially recommended by the local office of the United States Engineer Corps. We shall consider the effect of the bridge heights proposed in this plan as compared with certain modifications thereof; first, upon the bridge traffic, and second, upon the river traffic.

Barge and towboat designed for shallow rivers and low bridges in the United States

(a) Effect of Various Possible Bridge Heights upon the Traffic over the Bridge - Highway Bridges. -- The highway bridges carry two principal classes of travel. The first consists of vehicles moved by power, electric cars and automobiles, and of pedestrians. With this class an increase of gradient on the bridges or their approaches, within reasonable limits, simply means the expenditure of a moderate amount of additional energy without material loss of time, or other difficulties. The second class consists of horse-drawn vehicles a large portion of which do not enter the hill districts but are limited in their movements to the large district Iying on the lowlands of the three river valleys or accessible therefrom on moderate gradients. A great deal of this teaming consists of freight of all kinds received or shipped at the numerous freight stations on both sides of the river. The area accessible on roads of easy gradient from each end of these

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Last modified on 22-Dec 1999
Design format: copyright 1997-1999 Bruce S. Cridlebaugh
Original document: Frederick Law Olmsted, 1910