EARTH, SAND-CLAY, AND GEAVEL 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 



