224. | DISCUSSION ON 
drawback being the limited speed due to the fact that it was not 
feasible to put in the enormous superelevation necessary for high 
speed. This would be certain to make such lines locally unpopular, 
however beneficial to the country as a whole. The money cost of 
loss of time was difficult to estimate, but was probably not great 
in country districts. In the location of lines where it was desired 
to avoid earthwork by adopting sharp curves, the contour grade 
line was of the greatest value. After curvature, the most im- 
portant method of reducing (X) was by grading, but here great 
care was necessary, curvature and distance might be increased 
with but little addition to working expenses, but increasing the 
ruling grade altered the whole constitution of the line. The 
method of determining the most economical ruling grade was as 
follows :—Estimate the cost of building the line on several different 
ruling grades, and plot a curve represeriting the annual interest 
on first cost. (See Diagram). Then determine the curve of 
annual traffic cost, varying with the grade, and plot curve 
inversely. 
DIAGRAM. 
ANNY 
AL 
INTEREST ON FIRST cosp 
t 
GRADE IN FEET PER: MILE. 
: | | | | taste al re | 
to | 60 80 100 | 120 140 
ANN 
UAL WORKING | on 
—~ ENsy 
S. 
The position of the shortest vertical line intercepted by the 
two curves would indicate the ruling grade in feet per mile. 
Thus in the diagram the dotted line is the shortest vertical line 
; 
% 
