LOCATION OF COUNTRY ROADS.
The simplest form that this problem can take is that in which two points, as two towns, are to be connected by a road for the purpose of providing for a traffic between them, the nature and amount of .which is approximately known. In this case it is only necessary to examine the topography of the intervening country and select the line over which, taking into account the costs of construction and maintenance, the given. traffic may be most economically carried.
In most cases in practice, however, the problem does not have this simple character, and in fact location can seldom be determined by considerations of economy alone. The position of the line will be modified by local needs, such as the necessity of providing for the traffic of villages or farms intermediate between the ends of the road, which may often cause deviations from what would be the best line if the interests of the terminal points alone were considered.
Questions of the desirability of various lines for the comfort and convenience of travel, and the pleasure to be derived from the use of the road, dependent upon a;sthetic considerations, may also frequently operate to change the line from what would seem proper from a strictly economic point of view.
In thickly settled communities, as in most parts of the United States, the roads are in the•main. already located, the necessity for the location of new ones does not often arise, and when it does occur is usually mainly deter mined by the local needs and requirements of traffic.
The economic considerations involved in the location of roads are of two kinds: those relating to the accom modation of traffic, and those relating to economic conduct. The first deals with the necessity of the road to the community, the second with the cost of operat ing it. The first involves the general question of the
advisability of any road, and how it can be placed to give the greatest freedom to the movement of travel. The question is as to the value of the road to the gen eral community and its location to secure the greatest good for the least outlay, without taking into account the details of location which may affect the cost of transportation. The value of the road as developing trade in a town or bringing a farm nearer to market would enter into consideration. The accommodation of traffic requires that a road be located with a view to the convenience of its use by the largest portion of the traffic, as well as with a view of developing traffic.
The position of a road that will best accommodate traffic is that in which, other things being equal, the mass of traffic need be moved the least distance in reaching its destination; or, in other words, that for which if each ton of freight be multiplied by the dis tance through which it must be moved the summation• of the resulting products will be a minimum. If there be differences in the nature of the routes over which the road may be constructed, they may be considered as equivalent to changes in the relative effective lengths of line for purposes of comparison.
The ordinary problem of location deals mainly with considerations of the second class. It consists for the most part in the relocation of portions of old roads, of making such changes in position when improving a road as may tend to reduce the cost of conducting traffic over it and render it more convenient and pleasant for the use of travel, or of determining the details of alignment and grade upon a new road which is approximately fixed in position by the purpose of its construction.
The most economical location is that for which the sum of the annual costs of the annual costs for maintenance, and the interest on the cost of construction is a minimum.