Financial Considerations.
—While little has been said of financial considerations they are, of course, of prime importance. The amount of money as a whole that may be expended is usually limited by the taxes voted or the bonds issued. The planner must cut the garment according to the cloth. He must know the approximate unit costs of the roads that will be constructed as well as the mileage of the several types. To know this he must estimate the amount of traffic that will pass over the road, he should know also about what part of this is local and what part through, in order that a just division of the cost may be made between the local and larger units. If all the money of construction were to be furnished by the national government, say, and only through traffic were considered, directness and grades between controlling points would be the determining factors. But since local traffic cannot be excluded from the use of such roads it is but just that part of the cost of building be paid locally, and if so, that modifications in the lay out be made to accommodate the local conditions.
While the first cost of the road or the road system is of very great importance and will probably be the greatest influencing factor for any particular improvement or layout, the continued cost or cost covering a series of years approximating the life of the road surface should also have consideration.