Richmond times-dispatch. [volume] (Richmond, Va.) 1914-current, 1921-04-17
7COS7L Y 7ICHVA Y SITUATION
q S7IRS GOOD ROADSBUILDERS
Advocates Will Seek Ways and Means Whereby Engi-
neers May More Accurately Arrive at Justifable
First Cost and Methods of Financing.

type or types OF Improvement when
appear to him practicable If they can
hc financed out of the traffic saving
In other words. this method leaves TO
the engineer the same discretion as
H. now cuStomarily exercises in Selcv-
tion of design. but subjects it to tn"
test of financial Justification. This
saving in cost OF traffic operation per
ton mile when applied to the total
existing and potential increase in ton
miles gives the gross annual saving
IN traffic operation attributable TO the
government.
The net annual saving in traffic
operating costs is arrived AT by de-
Quoting from the gross annual saw
ing the Increase IL the annual high
way budget for interest. maintenance
and depreciation of the improvements.
In order TO obtain the annual cost
charEcablc To interest and dcprccii-
tion II is necessary To estimate the
economical life of the improvements
contemplated and take that amount
which AT the end of the period viii
have discharged all interest and re-
tired the principal.
Considerations which determine tho
economical life OF the Improvement.
or the period beyond which il may no
LONGER he maintained as such without
prohibitivc cost. involve not only a
study of the durability OF pavcmcnts
OF tn" various Tyr ;. but also the
durability OF the foundation and of
right of way. reduction Of grades.
elimination of curves and grade cross
inEs and installation of permanent
structures. etc. If these latter fca-
lures form Il considerable norton Of
the first cost tn" term in which traf-
nc saving is expected to pay for the
project should be corrcspondingiy
heightened If. moreover. n pavement
such as sheet asphalt or asphaltic
concrete is used. it may be renewed
at the end Of it's economical life with
out, as a rule, mourning any addi-
tionai expense for Foundation.
TO compare one type OF pavement
with another as to their durability,
the important point mus, not be
overlooked that renewal may he cX-
tcnsivc. or merely the renewed of the
surface. The most rational plan is
10 cStimat: first the durability and
cost of structure, etc, as Class |,
foundation as Glass H.. and surface
or wearing course as Class Ill. and
obtain weighted average Of dmra-
billy for the entire project in which
the factors would consist of the life
ana tho per cent Of cost OF each class
Of Improvement. Plate |. may he
used in determining the economical
lif" Of the Improvement.
I'm this chart, a life of 80 years is
assumed for class L.. 30 years for
class IL and from 10 10 80 years FOR
class III. improvements. From the
point at which the per cent OF total
cost lines for surface has" and Struc-
lures int"rScct for Il given project an
imaginary line is projected parallel
ng the l0ycar line il the surface is
estimated at 10 years; the 20-vcar
line. ii 20 years, or the 30-ycar line
II 80 years. Intermediate ages can
l." plotted between these limits. Tn"
intersection Of the projected line with
the base gives the average economical
life of the road or Investment.
AS an example. il is asccrtaincd
tina: class |. improvements represent
20 per cent: class H.. 10 per cent and
class III. 40 per cent Of the total
cost of Improvement This point is
located on the triavial diagram at
taD. IT the estimated life Of the
wearing course is 20 years. u line Alb
should be drawn parallel with the 20
year line intcrSccting the base line
at th), which shows an average eco
nomical life of - ID years for the
road ana also OF the period in which
the investment should be paid off.
AS the cost of the Improvement is
logically expressed in the form of
annual outlay FOR interest dcprccia-
zion and maintenance. platc IL may
conveniently be used to ascertain the
annual per cent of first cost required
for interest and depreciation over the
period covering the economical lie Of
the improvements. The curves are
plotted To show interest rates OF t.
: and L per cent: ordinatcs Show
terms of years and the abSciSScS SNOW
per cents Of total cost for combined
annual interest and depreciation.
Maintenance costs may increase or