Tensas gazette. [volume] (St. Joseph, La.) 1886-current, 1917-07-13
prepared by the United States Depart

Inc minimum width 10 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 Il shoulder not
less than three or four feet wide along
each side of the roadway proper. The
shoulders may have somewhat steep
er crown than the rest of the road
! surface, but they should be sufficiently
| fiat not TO endanger traffic using them
sHd 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 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 it is desirable, though not
customary. to increase the width of
the travelled way. A vehicle being
| drawn along a curved road tends to &C.
cupy an appreciably greater width
| than where the road is straight, and
unless the width of the travelled way is
increased cOrrespOndingly, 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 par
ocular 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
ment, which necessarily must be the
prime factor in solving this important
problem:
1. The cost of 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 sucf
that it is unnecessary to apply the
brakes to vehicles when descending
the grades. But for traffic where load,
are as important as speed, even yer!
light grades may be of considerable,
disadvantage.
2. Increasing the steepness of ;
grade decreases in three distinct way!
the load horse can haul: (a) for thu
same character of surface, the required
tractive effort or pull per ton of LOAF
is increased by about 20 pounds TO
each per cent increase i'm grade, %
the possible pull the horse can exert i
decreased by an amount equal to tn
effort required 10 lift his own weigh
through the rise. This amount is ap
proximately equal to one One-hun
dredth of the horses weight for eacl
per cent increase in grade, (c) the ef
fective pull of the horse is reduced b.
the change in the angle at which tn
pull is applied.
3. The pull horse can exert on
level road varies greatly with the In
dividual animal, and is affected by tn
manner of hitching 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 puDli
roads and rural engineering indicat
that, on a level road, average farr
horses unframed to the road can eXer
steady pull for several cOnsecutiv
hours equivalent to from 0.OS to o.
of their own weight without undu
fatigue, and that by resting at inter
walls of from 500 to 600 feet they ca
exert a pull equivalent to about o.
of their weight, provided the foOthOl
, is good.
4. The tests referred to above ais
indicate that with a well-cOnstructe
wagon the pull required to move
gross load of one ton over level roa
varies about as follows:
Pound
Loose sand road ...........................3
Average dry earth road varies
| Firm earth or sand-clay road.
| Average gravel road neutrality-suspicious..
} | Ffrst-class gravel or macadam road.
In general, the judgment should b
2 largely influenced, in fixing the max
| mum grade, by the topography Of I'll
2 region which the road traverses. A
cOrding to the best current practic
where the road is or Is expected to b.
come of sufficient Importance to wa
rant highly improved surface, ii
maximum grade usually is fixed wit
reference to this feature about as 70
|. lows:
. Per cen
Coastal plain and prairie regions. q TO
I | Average rolling country ..............4 10
1 OF opin N