56 BULLETIX 463, U. S. DEPARTMENT OF AGRICULTURE. 
The construction method described above is modified quite fre- 
quently by omitting the subgrade trench and the rolling. The prac- 
tice followed in many localities is simply to grade up the roadbed and 
heap gravel along the central portion. Traffic is then depended upon 
to spread and compact the gravel and produce a uniform surface. 
While some of the roads constructed in this way are great improve- 
ments over the original earth roads they nearly always are crowned 
too much for comfortable driving, and seldom wear as well as when 
the more careful method of construction is followed. It is believed, 
therefore, that in the long run it pays to employ a trenched sub- 
grade and to compact the surface by rolling, though a possible ex- 
ception to the economy of a trenched subgrade may exist where good 
gravel may be obtained very cheap. In this case it may be cheaper 
to surface the entire roadway than to incur the additional expense of 
trenching and constructing earth shoulders. 
COST OF GRAVEL ROADS. 
In estimating the cost of a gravel road it is necessary to consider 
(1) the cost of grading and preparing the subgrade, (2) the pur- 
chase price of the gravel it is proposed to use, (3) the cost of de- 
livering the gravel on the road, and (4) the cost of spreading and 
compacting the gravel. 
The cost of grading has been discussed in connection with earth 
roads and need not be considered here. But it should be borne 
in mind that the cost of preparing the subgrade, after the rough 
grading is complete, depends to a very considerable extent upon t he- 
degree of care exercised in doing the latter work. The character of 
the soil composing the roadbed also may be an important factor in 
determining the cost of preparing the subgrade, especially if any 
considerable period of time elapses after the completion of the rough 
grading before the subgrade is prepared. Some soils remain loose 
indefinitely and are worked into proper shape easily, while others 
may become hard and compact in a very short time after being placed 
in a roadbed. 
Where a road has been graded previously with moderate care and 
has not settled out of shape or been allowed to erode, and where the 
price of labor is about 20 cents per hour and of teams about -±0 cents 
per hour, the cost of preparing a subgrade for a gravel road sur- 
face varies about as follows: 
Cents 
per square 
yard. 
Light loam soil 13 to 2 
Light clay soil, freshly graded 2 to 4 
Stiff clay soil, freshly graded 3 to 5 
Stiff clay soil, thoroughly compacted 5 to 8 
