during which the
public is being benefited. Better prices are obtained on contracts for
a large mileage than for smaller jobs, and the community can receive
the benefit more quickly than where construction proceeds piecemeal
with current funds. The vital consideration is to insure that the term
of the bonds is well within the useful life of the road, and that
ample provision is made to maintain the roads during that period.
Under proper restrictions the bond method of financing is to be
commended. The bonds are an attractive investment and readily
marketable on satisfactory terms.

CHAPTER III

DRAINAGE OF ROADS

=The Necessity for Drainage.=--The importance of drainage for all
roads subject to the effects of storm or underground water has always
been recognized by road builders, but during recent years constantly
increasing attention has been given to this phase of road
construction. It is unfortunate that there has in the past been some
tendency to consider elaborate drainage provisions less necessary
where rigid types of surfaces were employed. It has become apparent,
from the nature of the defects observed in all sorts of road surfaces,
that to neglect or minimize the importance of drainage in connection
with either earth roads or any class of surfaced roads is to invite
rapid deterioration of some sections of the roadway surface and to add
to maintenance costs.

The degree to which lack of drainage provisions affect the
serviceability of the road surface varies with the amount of
precipitation in the locality and the manner in which it is
distributed throughout the year. In the humid areas of the United
States, which are, roughly, those portions east of a north and south
line passing through Omaha and Kansas City, together with the northern
part of the Pacific slope, precipitation is generally in excess of 30
inches per year and fairly well distributed throughout the year, but
with seasonal variations in rate. In these areas, the effect of the
precipitation, both as regards its tendency to lower the stability of
soils and as an eroding agent, must be carefully provided against in
highway design.

Outside of the areas mentioned above, the precipitation is much less
than 30 inches per year and its effect as an agent of erosion is of
greatest significance, although in restricted areas there may be short
periods when the soil is made unstable by ground water.

=Importance of Design.=--The drainage sys