The Arvada enterprise., 1917-06-21
prepared by the United States Depart
ment of AgricuIture

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 10 feet, though
q 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 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 20 feet where horse-drawn trafac
predominates, 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 &C.
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 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
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
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 must be the
prime factor In solving this important
problem:
1. The cost Of average pleasure traf-
fic. hOrse-drnwn and motor, IL praou-
cally unaffected by grades Of not more
than 6 or per cent (slx or seven feet
rise per 100 feet, measured horizontal
w, provided the conditions are such
that 1t IL unnecessary to apply the
brakes to vehicles when descending
he 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
grade decreases in three distinct ways
the load IL horse can haul: (a) for the
troc,;y. osror, mr. null nar m, 81 ,noI
Ia ,ncro,sed ty .hou, % wounds for
,,ch nor co,, ,,craos. +, rroLo m,
,ho nossI,,o mi, ,ho horsa can ox.r, !,
Jo.ro,.oI hr nm o,noun, .,uo, IN tho
,nor, rooriroI n Iirt bis nwn wc,yht
thror,h ,ho ,iso mi, o,n,,,,t f., nm.
,roxImo,oIv anna, IN ana o,o.bun.
.,r.,,,b ~ Tho horo,,, uo,nh, ,or zach
nor con, Increase In grade n, H.. of.
! fcc,,ve mil nj IN. horse 10 r.Lucod hv
rho cbonco in tho on,,e nj which the
nj, IL, ,,,,,,.,,
pun is "ppicu'
e The mil n horse cnn exert IN n
i...., - ~. -....., ,., -, H.,
ieNel roau varies greutIy with the IN
| tliyiduul nnimul. and il Infected nv the
n,,,,,n. 90 ,,I,oi,,,,,, .,,l ,,,s I'm -, ,i,.,
driver Th. oh.ron,or ~, a.. road
surfoco also mny hnva nm ,mnor,ont
lnauonco nv ,noc,in, TIM ,ocnri,v n,
,ho horso.. ron,hoid
Te.,s modc hv m, or,c. ., ,,h,,c