EARTH, SAND-CLAY, AND GRAVEL ROADS. 33 
with scrapers or hand tools alone, and the cross section is, therefore, 
frequently left approximately flat. The grading machine is then 
used, in the manner already described, to produce the required cross 
section. 
After the road has been finished with the * grading machine, it 
should be given frequent attention until the embankments have fin- 
ished settling and the surface has become thoroughly compacted by 
the action of traffic. Generally a period of several months should 
elapse after a road is graded before it is considered complete, and 
such settlements and irregularities as develop during this period 
should be corrected by the use of either a grading machine or a road 
drag. A description of the road drag and a discussion of its uses 
are given on page 58. 
CONSTRUCTION COSTS. 
Aside from drainage structures, the principal item of cost attached 
to the construction of an earth road is for the grading. The cost of 
grading varies greatly, according to the condition of the weather, 
the nature of the material to be excavated, the efficiency of labor, 
teams, and machinery, etc., and seldom can be estimated in advance 
with any great degree of accuracy. On this account average costs 
based on past experience may be very misleading when applied to a 
particular project. In the following statements and data an effort is 
made to show the approximate range of cost rather than the average. 
The first step in estimating the cost of grading a given road is 
to ascertain the quantities of work to be done. After the quantities 
have been determined the cost may be estimated in either of two 
ways. First, the organization for carrying on the work may be 
planned in detail and the estimate arrived at by considering the 
cost of maintaining such an organization, together with the rate at 
which it may reasonably be expected to accomplish the work. 
Second, the cost per cubic yard for excavation and the cost per 
mile for shaping the roadway may be estimated at flat rates. The 
first method is the most accurate, though the latter is the one 
employed most frequently. 
If the prices for labor and teams are known, the cost of grading 
under a given set of conditions may be estimated from the data 
already given. A frequent source of error in estimating costs in 
this way is that such items as supervision, lost time for which pay- 
ment must be made, repairs to tools and machinery, and depreciation 
of the plant are overlooked. 
The following data (Tables 5 and 6) are intended to furnish a 
rough guide in making estimates of grading cost at a flat rate per 
cubic yard. They are based on labor at 15 cents per hour; horses 
61531°— Bull. 463—17 3 
