TRANSPORTATION ON LAND BY VEHICLES: -THE ROADS 45 



That part of the road, however, which lies more than 4 feet below the original surface of the slope 

 is apt to be free from roots, and particularly from heavy stumps, the removal of which is more costly, 

 usually, than that of rock of equal volume. 



For a 16 foot road built on solid basis (the dirt removed being wasted), the grade of the mountain 

 slope traversed influences the expense of building as follows, if dirt is removed at 15 cents per cubic yard:- 



Qrade of slope 

 20", 

 40 7o 

 60 7o 

 80% 

 (G) GR.ADIXG: — 



I. According to the disposition made of the dirt in a road line, the following systems may be 

 distinguished : — 



(a) Shifting dirt "sideways." 



1. Building on solid foundation and wasting all dirt by throwing it overboard. 



2. Building road on partly solid foundation, with, without, or with partial breastworks to retain 

 the filled part of the roadbed. 



(b) Shifting dirt "lengthways" -system of equal cuts and fills -usually adopted in railroading, and 

 in road building in the Old Country; 



(c) A combination of the systems given under a and b. 



II. Where dirt is shifted sideways, the following points must be considered :- 



(a) Steepness of slope; 



(b) Width of road; 



(c) Composition of the soil; 



(d) Availability of suitable timber or stone for breastworks. 



While the expense of excavating in case of roads built on half solid foundation approximates one 

 quarter only of the expense incurred for roads built on solid foundation, a scarcity of stone or timber 

 suitable for breastworks may lead to the adoption of the latter method. 



Where dirt is moved sideways, the road follows the natural contours of the topography. 



III. Where dirt is shifted lengthways there must be considered :- 



(a) The length profile. From the grade found between consecutive points of the road and from 

 the length of the sections between them, the relative and the absolute elevations of all section points are 

 ascertained. 



The elevations as well as the section -lengths are plotted on profile paper, the former usually on a larger 

 scale than the latter. 



The lines of junction presented on the paper require raising in one and sinking in another place, so 

 as to improve the grade of the road. The dirt volume of the "cuts" should be equal to the dirt volume 

 of the "fills." To that end, a preliminary line (or a silk thread) is drawn on the paper in such a way 

 that the areas of the length profiles of cuts and fills, found above or below the preliminary line, are fairly 

 equalized. Care should be taken to provide that all dirt is moved down hill. "Borrow pits" should be 

 avoided. A good road engineer gets along with the dirt found on the line of the road ; and he does not 

 "waste" any dirt obtained from cuts. 



(b) The cross profiles. "Cross profiles" taken at the various section points further facilitate the 

 equalization of cuts and fills. Any road instrument may be used for the field survey of cross profiles. 

 A straight board, e. g., the length of which equals the width of the road and which has a plumbob 

 attachment to secure its horizontal position, is used for the taking of cross profiles on dirt roads. The 



