The following is taken from “Modern Road Construction – A practical Treatise on the Engineering Problem of Road Buildign, with Carefully Compiled Specifications for Modern Highways and City Streets and Boulevards. Published 1917.
Page 35 –
Width of Road.
A road should be wide enough to accommodate the traffic for which it is intended, and should comprise a wheelway for vehicles and a space on each side for pedestrians.
The wheelway of country highways need be no wider than is absolutely necessary to accommodate the traffic using it; in many places a track wide enough for a single team is all that is necessary. But the breadth of the land appropriated for highway purposes should be sufficient to provide for all future increase of traffic. The wheelways of roads in rural sections should be double; that is, one portion paved (preferably the center), and the other left with the natural soil. The latter, if kept in repair, will be preferred by teamsters for at least one-half the year.
The minimum width of the paved portion, if intended to carry two lines of travel, is fixed by the width required to allow two vehicles to pass each other safely. This width is 16 feet. If intended for a single line of travel, 8 feet is sufficient, but suitable turnouts must be provided at frequent intervals. The most economical width for any roadway is some multiple of eight. Wide roads are the best; they expose a larger surface to the drying action of the sun and wind, and require less supervision than narrow ones. Their first cost is greater than that of narrow ones, and nearly in the ratio of the increased width.
The cost of maintaining a mile of road depends more upon the extent of the traffic than upon the extent of its surface, and unless extremes be taken, the same quantity of material will be necessary for the repair of roads, either wide or narrow, which are subjected to the same amount of traffic. The cost of spreading materials over the wide road will be somewhat greater, but the cost of the materials will be the same. On narrow roads the traffic being confined to one track, will wear more severely than if spread over a wider surface.
The width of land appropriated for road purposes varies in the United States from 49½ feet to 66 feet; in England and France from 26 to 66 feet. And the width or space macadamized is also subject to variation; in the United States the average width is 16 feet; in France it varies between 16 and 22 feet; in Belgium 8j feet seems to be the regular width, while in Austria, from 14¼ to 26½ feet.