10 BULLETIN 136, U. S. DEPARTMENT OF AGRICULTURE. 
of the adjacent land. On each of the six radial market roads which * 
have been assumed for the calculations above there would be a traffic 
area of 4,021 acres and a farm area of 2,614 acres per mile. 
COST OF HIGHWAY CONSTRUCTION. 
The cost of a given type of highway varies, but the range of variation 
has become comparatively well defined for each type within a given 
region. The standard of construction for any given type is now also 
generally understood and adhered to in the best practice. As this 
standard becomes more generally adopted, the price variation for 
similar local conditions will become less. In Table 5 there are given 
examples of cost per mile for three types of modern State highways. 
These averages are taken from lists of State construction jobs which 
are tabulated in Appendix C.1. The standard which present specifica- 
tions represent is a necessary standard evolved as the result of 20 
years of modern road building. When these standards are ignored, 
it is usually at the expense of good work. 
TABLE 5.—Cost elements of three types of highways.} 
| 
Drainage | ‘Drainage | 
Type. and (Surfacing.| Total. and Surfacing. 
grading. | grading. | 
} 
| Per cent. | Per cent. 
| 
} 
Graveli(@20 feetiwid ©) ast sae eae ee eee ene rae $1,817 | $2,599 $4, 416 41.15 | 58. 85 
Ordinary or water-bound macadam (15 feet wide)...-- 3, 400 5,815 9,215 36.90 | 63.10 
Bituminous macadam (15 feet wide) ?.......-.-------- 2,765 | 7,933 10, 298 26.85 | 73.15 
1 These cost elements were obtained from 87 gravel jobs and 104 macadam jobs in Maine and New Jersey, 
and from 53 bituminous-macadam jobs in Maine, Massachusetts, and New Jersey. The averages were 
computed by weighing each job with its relative ‘length and reducing all costs by simple proportion to 
equivalent average widths of 20 feet and 15 feet respectively. The complete tables of cost elements on the 
244 jobs are given in Appendix C. 
2 Includes eight jobs of bituminous resurfacing. (See footnotes, Appendix C.) 
The cost of highway construction may be subdivided into (a) cost 
of enduring features and (b) cost of perishable features. When roads 
are built with accepted standards of grade, alignment, drainage 
structures, and foundations, the cost of such elements may be charged 
for enduring features. Whether roads so built result in the maxi- 
mum percentage of permanent investment depends in part upon the 
cost and nature of the wearing surface. For example, a highway 
completed with all the best enduring features and then surfaced with ~ 
gravel would show a higher percentage of cost for enduring features 
than the same road surfaced with more expensive material, as ordi- 
nary macadam or bituminous macadam. A poorly constructed gravel 
road, however, where enduring features had been shghted, would 
present a very high percentage of charge for temporary features. 
Macadam roads, so called, have been built with bond money by 
simply spreading broken stone in the mud. An example is shown in 
Plate I, figure 2. 
1 These examples were selected from States in which records were kept so as to permit cost analysis. 
