PART II
Main Thoroughfares
Width of Thoroughfares
In considering the economical widths for the main thoroughfares of a city, so many complex factors are involved that no exact and indisputable conclusions can be reached; but there are certain facts and principles that ought to remove such decisions from the realm of purely arbitrary whim and custom by which they are now generally settled. Practically every normal main thoroughfare, even of the most compact type, must provide for car tracks in the middle. On straight runs, according to the present practice and with the new cars in Pittsburgh, the width occupied from the outside of one car to the outside of the other is 17 feet 8½ inches. At that, the cars are narrower than the modern standard in some other American cities, and the clearance between the cars is reduced to less than a reasonable requirement for safety. On curving roads, such as the Pittsburgh topography often imposes, the space occupied is greater. Without allowing any clearance on the outside, a space not less than 18 feet, and preferably more, should be allowed for the actual cars on straight runs.
In Pittsburgh, the gauge of the car tracks was originally made to conform to the prevailing local gauge of other vehicles, on the mistaken theory that it was desirable to have the smooth tracks used by wagons; and this has resulted in the almost invariable conformity of the wagon gauge to that of the tracks, regardless of the size or character of the vehicle. With the added fact that Pittsburgh pavements are prevailingly bad, and that the form of rail is such that it is very difficult for a wagon to turn out when it has once got into the track, the teamsters in Pittsburgh are more inveterate in the habit of driving in the car tracks, and less ready to turn aside for cars or other vehicles, than in most cities. The severe and constantly repeated strain of the horses, which is required to wrench heavily-loaded wagons free 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 2½ 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 the car tracks. About 7 feet over all is now the ordinary maximum in Pittsburgh, a few auto trucks and delivery vans exceeding that figure slightly, and an occasional three-horse team occupying over 8 feet. In New York and Boston, wagons measuring from 7 to 8 feet from hub to hub are common, and they sometimes considerably exceed 8 feet.
Just as in the case of steam and electric railway equipment, the tendency is constantly in the direction of heavier, longer, wider vehicles, for the sake of the operating economy due to large units; and, with the steady increase in the use of motor vehicles for business purposes, this tendency is likely to be greatly accelerated. There is every reason to expect that motor trucks will gradually increase in size until a limit is fixed by the public authorities in order to protect the pavements, and for the sake of standardizing the lines of travel in relation to the street widths. But, in the interests of economy of operation, the limit should be as high as practicable, probably not less than 8 feet.
If 8 feet be allowed for each vehicle, plus only a foot of clearance, the cars and one row of vehicles on each side, between them and the vehicles standing at the curb, would require 54 feet between curbs. A wagon backed up to the curb on a busy street will seriously discommode travel at that, and the clearance allowed is very small. A width of 54 to 60 feet between curbs is, therefore, highly desirable in the main thoroughfares.