The Idaho recorder. [volume] (Salmon City, Idaho) 1886-1927, 1917-07-06

fIFGuATE1
ment OF Agricuiture)
The minimum width to accommodate
safely two lines Of average horse
drawn traffic Is ii feet, and for auto
mobile traffic the width preferably
should be not less than IS feet, though
"A width of 16 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 shoulder not
less than three or four feet wide along
each side OF the roadway proper. The
shoulders may have a somewhat steep
or crown than the rest of the road
surface, but they should be sufficiently
fiat not 10 endanger traffic using them
and really should constitute an addi-
tional width of roadway. This means
thut the total width of roadway be-
tween side bitches never should be less
than 20 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 II is desirable, though not
customary, TO 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 correspondlngly, this ten
dency contributes materially to the
hazards that invariably accompany
sharp curves. The minimum widths
given above should also be increased
on embankments 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
iy 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 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-
inent, which necessarily must be the
prime factor In solving this important
pTnblsm:
1. The cost of average pleasure traf.
Nc. horse-drawn and motor, Is practi-
eslly unaffected by grades of not more
than 9 or Z per cent (six or seven feet
iiae per 100 feet. measured horizontal
ly), provided the conditions are such
that II Is unnecessary to apply the
brakes to vehicles when descending
the grades, But for traffic where loads
are as important as speed, even very
light grades may be of considerable
disadvantage.
2. Increasing the steepness OF a
tho load n horse can haul. (a) for the
same character of surface. the required
tractive 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,
prnNimately equal to one one-hun,
| dretlth OF the horses weight for each
per cent Increase In grade, (c) the eff
fertlve pull of the horse is reduced hy
the change in the angle at which tn,
| pun II applied.
3, The pun horse can exert on a
level read varies greatly with the In
| diVidIAl animal. and Is affected by the
manner Of hltchiug aud the skill OF IN,
/ driver. The character " the road
surface also may have an important
influence by affecting the security OF
The horses foothald.
Tests made by the office of public
ruadS and rural engineering indlcat,
that, on a level road, average farm
horses uutraiRed To the road can ex,rt
= steady pull for several conscCutiy,
hours equivalent to from OuS 10 OIL,
of tLcir own weight without undu,
fatigue aud that 10y resting at inter
walls If from $40 70 COO feet they ear
exert pull equivalent TO about o..
NJ their weight provided the foothol,
"a good.
T. The tests referred Ia above ais,
Indicate that with well-constructe,
~agoS the pull required to move 8
gross load or one ton over level roo,
varies shout as follows:
lsNose sand road ..-........... NJ
Average dry earth road N,ariss
rtt"'Ael '-rstssr.. ...r.,. ......-... x
tlrm earth or sand-clsy read H.
sNeraEe gravel ruad ............ :
FUst-e'aSS graVel or maCadarn road
In general, the Judgment should h.
largely Influenced, in fixing the maxf
mum grade, by the topography of m,
region which the road traverses. Ac
sorting TO the best current practice