OBJECT OF ROADS.
The expediency of any proposed road construction or improvement depends upon its desirability as affect ing the comfort, convenience, and health of residents of the locality, and also upon its economic value, which is largely, determined by its cost and durability, as well as upon the facility it gives for the conduct of traffic.
The desirability of a road surface for any particular use depends both upon its fitness for the service required of it and upon its durability in use.
Upon a country road, the problem of improvement ordinarily consists simply in providing the hardest and most durable surface consistent with an economical expenditure of available funds, the object being to lighten the cost of transportation ' by reducing the resistance to traction, and to render travel easy and comfortable.
Upon city streets, however, several other factors may be of importance in the design of highway improvements.
The comfort both of those using the street and of the occupants of adjoining property will be largely affected by the freedom of the surface from noise and dust.
The safety of the pavement in use, its effect upon the health of residents of the locality, and its economic value must in each case be considered.
To adjust to the best advantage these various ele ments, frequently quite discordant with each other, is a matter which can only be accomplished by the exer cise of good judgment. Local conditions and necessi ties must always be considered — such as the difficulties of drainage, the availability of various materials, the nature of the traffic to be carried, and the needs of the business or property interests of the neighborhood. Thus, for heavy hauling of a large city, the durability and resistance to wear of the pavement may be the paramount consideration; for an office district, quiet may be very important; for the lighter driving of a residence street, the elements of comfort and health fulness may properly be considered as of greater force than the purely economic ones; while in all of the cases the necessary limitation of first cost will largely determine what may or may not be done.
The problem of the highway engineer, in designing works of this character, involves the consideration of these various elements and their proper adjustment to give the best results.
The kinds of road surface most commonly employed are as follows: For the streets of cities and towns, pavements of stone blocks, brick, asphalt, and wood; for suburban streets and important country roads, macadam and gravel surfaces; for ordinary country roads in general, surfaces of earth or gravel.