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from the tracks, is, in the aggregate, a serious economic loss; and the delays not only to the street cars but to all forms of wheeled traffic, caused by the conditions described, are incalculably great. But even good pavements and the use of a grooved rail would not cure the trouble in Pittsburgh streets as now laid out, because, almost universally, there is not sufficient room for a vehicle to pass between the cars and another vehicle standing or slowly moving next the curb.

In every street, vehicles must be free to stop for loading and unloading, and on a busy thoroughfare the space next the curb is so much used in this manner as to become merely a series of sidings into which slow-moving vehicles can turn from time to time in order to clear the main passageway. The result of the conditions above described is that practically the whole wheeled traffic in Pittsburgh streets is inevitably concentrated on the eighteen-foot width where the cars run. The extent to which this reduces the average speed of travel and the total capacity of the thoroughfare has been strikingly illustrated for Pittsburghers by the contrast of the former sluggish congestion of traffic on Smithfield Street with the sparse appearance and rapid movement of the same traffic since the "one-way" regulations have made it possible to get one free line in each direction for moving vehicles separate from the cars. The same striking increase in capacity is to be secured, without the grave inconveniences and drawbacks of the "one-way street" regulations, where the space between the cars and the curb can be made wide enough for two lines of vehicles, instead of just enough for one or for one and a half, as is usual in Pittsburgh.

It is very difficult to determine just what is the most economical allowance of width. There is much variation in the widths of the vehicles themselves, and the necessary amount of clearance varies with the average skill of the drivers and with the effectiveness of the police control. The width of the line is plainly determined by the widest vehicles in it rather than by the narrowest. In Pittsburgh the customary width of the heavier and wider wagons is now controlled by the practical necessity of fitting the wheels to the railway gauge of 5 feet 2-1/2 inches, and the widths are considerably less than prevail in New York, Boston, and other reasonably well-paved cities where the wagons are not fitted to

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