Western liberal. (Lordsburg, N.M.) 1887-1919, 1917-06-22
prepared BY the United States Depart

ment OF Agriculture)
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 IS feet, though
a width Of 10 feet is used frequently.
In order to maintain the travelled way
to the required width and to afford
proper safeguards against accidents, 1t
Is necessary to provide a shoulder not
less than three OF 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 mean
that the total width Of roadway be-
tween side bitches never should be less
han 20 feet where horse-drawn traffic
pr~edominates, and "a feet where any
considerable volume of automobile
traffic is to be accommodated.
Where sharp curves occur in the
alignment 1t is desirable, though not
customary, to increase the width of
. the travelled way. A vehicle being
drawn along a 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 cOrrespondlngly, this ten
= dency contributes materially to the
hazards that invariably accompany
sharp curves. The minimum widths
given above should also be increased
on entertainments 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 a 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 a 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-
ment, which necessarily u be the
prime factor in solving this important
problem:
1. The cost of average pleasure traf-
fc, hOrse-drawn and motor, is praCti-
cally unaffected by grades of not more
than g or : per cent (six or seven feet
rise per 100 feet, measured %hOrlzOntal-
ly), provided the conditions are such
that it is unnecessary to apply the
brakes to vehicles when descending
he grades. But for traffic where loads
are as important as speed, ever very
light grades may be of considerable
disadvantage.
.. Increasing the steepness of a
grade decreases in three distinct ways
die load a horse can haul; (a) for the
same character of surface, The required
.%ractive effort or pIll per ton of load
) increased by about 20 pounds for
,ach per cent increase in grade, (b)
he possible pull the horse can exert Is
decreased by an amount equal to the
fort required to lift his own weight
through the rise. This amount is APP
aroxlmately equal to one One-hun
lrcdth of the horses weight for eacl
DER cent increase in grade, (c) the eff
fcctlve pull of the horse is reduced by
the change in the angle at which thu
pull is applied.
3. The pull a horse can exert on
level road varies greatly with the in
divldual animal, and is affected by tn
manner of hitchlng and the skill of tn
driver. The character of the rOa,
surface also may have an importan
influence by affecting the security o
The horses foOthOld.
Tests made by the Office of publ
roads and rural engineering indicat
that, on a level road, average farI
horses unframed to the Dad can exeI
a steady pull for several consecutlv
hours equivalent to from O.OS to OIL
Of their own weight without undu
fntigue. and that by resting at inteI
walls of from 500 to 600 feet they ca
exert a pull equivalent to about o.
of their weight, provided the foOthOl
is good.
1. The tests referred to above ais
Indicate that with a wel%l-constructe
wagoS the pull required to move
gross load Of one ton over a level rOa
varies about as follows:
Pound
SSSSs ss"' dry hS3 earth road &aries
.Breatlyl s,.'-...S .t...',.s
Average gravel road .........".";'''
First-class gravel or macadam road.
In general, the judgment should
largely Influenced, in fixing the MAJ
mum grade, by the topography OF Il
region which the road %traverses. A
-cording to the best current practC