Wausau pilot. [volume] (Wausau, Wis.) 1896-1940, 1917-06-26
prepared by the United States Depart
ment of Agriculture0

HsHt Oh ASrlculture.)
The minimum width to accommodate
safely two lines of average horse
drawn traffic is IA feet, and for auto.
mobile traffic the width preferably
should be not less than 10 feet, though
width of l6 feet is used frequently
| In order TO maintain the travelled way
| to the required width and to afford
| proper safeguards against accidents, ii
| is necessary to provide a shoulder not
| less than three or four feet wide along
each side of the roadway proper. The
| shoulders may have a somewhat steep
! er. crown than the rest of the road
surface, but they should be sufficiently
fiat not to endanger traffic using them
and really should constitute an addi-
tional width Of roadway. This means
that the total width of roadway be-
tween side bitches never should be less
than ~ feet where horse-drawn traffic
predominates, and "a feet where any
considerable volume of automobile
traffic is to be accommodated.
Where sharp curves occur in the
alignment it is desirable, though not
customary 10 increase the width of
the Travelled way. A vehicle being
drawn along curved road tends to oc-
cupy an appreciably greater width
than where the road is straight, and
unless the width of the travelled way is
increased correspondence, this ten
dency contributes materially to the
hazards that invariably accompany
sharp curves. The minimum widths
given above should also be increased
on embellishments of any considerable
depth, so as TO make maintenance
easier and at the same time diminish
the danger of accidents.
The width of right of way required
to provide all necessary area for the
roadway, slopes and bitches, varies
considerably with the nature of the
topography.
Grades.
In designing public road one of the
most difficult problems to solve proper
ly is the question of maximum allow
able grades. In deciding this question
the advantages to be gained by reduc-
ing all of the sleeper grades on a par
ticular road to given maximum
should be weighed against the addi-
tional cost which the reduction in
wolves.
The following data and suggestions
are intended TO aid individual judg-
which ne nil hO 4hn
prime factor in solving this important
problem:
1. The cost on average pleasure traf-
fic, horse-drawn and motor, is practi-
cally unaffected by grades of not more
than 6 or per cent (six or seven feet
rise per 100 feet, measured horizontal
ly), provided the conditions are such
that it is unnecessary to apply the
brakes to vehicles when descending
the grades But for traffic where loads
light grades may be of considerable
disadvantage.
2. Increasing the steepness of a
grade decreases in three distinct ways
the load horse can haul: (a) for the
same character of surface, the required
tractiva effort or pull per ton of load
Is increased by about 20 pounds for
each per cent increase in grade, (b)
the possible pull the horse can exert is
decreased by an amount equal to the
effort required to lift his own weight
through the rise. This amount is ap-
prOximately equal to one one-hun-
dredth of the horses weight for each
per cent increase in grade, (c) the eff
fective pull of the horse is reduced by
the change in the angle at which the
pull is applied.
3. The pull horse can exert on
level road varies greatly with the in
dividual animal, and is affected by the
manner of hitching and the skill of the
driver. The character of the road
surface also may have an important
influence by affecting the security of
the horses foothold.
Tests made by the office of pubic
roads and rural engineering indicate
that, on a level road, average farm
uOIScS uulIul1cu W TIE TOdu can exert
a Steady pull for several consecutive
hours equivalent to from 00S to 0.10
of their own weight without undue
fatigue, and that by resting at inter-
walls of from 500 to 600 feet they can
exert a pull equivalent to about OBS
of their weight, provided the foothold
is good.
4. The tests referred to above also
indicate that with a well-constructed
wagon the pull required to move a
gross load of one ton over a level road
varies about as follows:
Pounds.
Average dry earth road (varies
greatly -.....ssr.....-......... LOU
Firm earth or sand-clay road ..1O5
Average gravel road ...................... SO
First-class gravel or .macadam road. So
In general, the judgment should be
largely Influenced, in fixing the maxi
uIID, grade nv the tODoorra uhv of fhp