n1ent. Ho\vever, it was a rando1n pattern
in the sense that no systematic approach
\vas used; the road system "'as planned fron1 year to year to n1ect an annl.lil cut of 20 n1illion board feet. During 1951, i.n contrast, a systen1atic pattern \Vas tested in planning the remaining 43 1niles of road v,rhich included the north side of -. Lookout creek, illustrated in Figure 2. These t'<vo road patterns, then, provided a basis for the con1parison reported here. l
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Pri-nciples_ of-:Rcfad Planning-...
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'"A search of American _3.nd European
literature was of little a\'ail in proYiding
- - the- principles of road planning - for
-rnountainous terrain. The \vay a syste­
platic pattern _v;:as developed for the H.
J. Andrews Expcri1nental Forest can best
be illustrated by considering a very
siinple forest drainage, as in Figure 3.
A typical road systen1 fOr this drain­
·age, Figure 3-a, _consists of several take­
offs fro1n the main ro'ad and many spurs.
An i111proveri1ent over such a pattern has
lqng een _ de1nonst_rated for flat and_ _uni­
formly_sloping
.that is, a-srstem of
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areis;_
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_roads spaced a_t the "ecOnomic"­
·parallel
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interval; the interval at which road and
·yarding costs balance to give a minin:1um
cost. Applying this idea to our simplified
AIR VIEW of the H. J. Andrews Experimental Forest in Oregon, looking eastward toward
the summit of the
ascade Mountains. General characteristics of road pattern are shown.
drainage might give a pattern of roads
switchbacking at regular intervals, such
as Figure 3-b, or one clin1bing at maxi­
mum grades in the same direction as the
main road, as in Figure 3-c. But these
alternatives result in n1ore road than is
needed to log the timber, and most of
the roads are on steep gradients.
A pattern that v:ill overcome these ob­
By ROY R. SILEN.
jections can be developed by locating
Pacific Norlhwest Forest & Range Experiment Station, Fore$! Service, U. S, Department of Agrkulture
most of the roads parallel to the main
road and using a single climbing road to
MPROVEMENTS in the pattern and
serve settings and marked on the ground.
join the levels, as Figure 3-d. Thus, the
efficiency of roads on the H. J. An­
Lookout creek is typical of most drain­
basic principle for a systematic road pat­
drews Experimental Forest have re­
ages in the Oregon Cascades. Stream pat­
tern is: Red11ce the n11mber of roads that
sulted from the development and appli­
tern is complex, and elevations range
clhnb bettveen levels (tnd increase the
cation of a few simple principles for
from 1500 feet at the mouth of the creek
propo1"1io11 of the drainage served by wad
reducing road length. lhis· advancement
to a rim of peaks 2500 to 5200 feet
levels spaced at the econo1riic interval.
stems from the station"s pilot plant stud­
high. Only about one-fifth of the area is
The term road level here implies parallel
ies into the use of cotnplete: forestry­
in benches and gentle topography. The
roads of any grade but so far as possible
logging plans in placing a virgin forest
remainder is steep with occasional rock
located with gentle favorable grade .
area under management. The beginning
outcropping. Old lava flows have formed
Of cOurse, few drainages are as simple
of this work is described in Robert Auf­
lines of bluffs at some elevations. The
<lerheide's article "Getting Forestry into
drainage is covered mostly _ with a 400- ­ as that in the illustration. Usually, side
slopes are cut up by. triQutary drainages,
the Logging Plan"" in THE TIMBERMAN,
year-old Douglas fir stand in various
and distances from stream to ridgetop
March 1949.
states of preservation, but many patches
vary greatly. As a result, the number of
The H. J. Andrews . Experimental
of young growth are found near the
Forest, established in 1948, includes the
road levels on slopes must change from
ridgetop where crown fires killed the old
place to place. On the north side of Look­
entire -15,000-acre drainage of Lookout
stand.
creek in the Cascade mountains about
out creek, for example, three road levels
Two contrasting road patterns, one
are enough northwest of McRae creek, ·
50 miles east of Eugene, Ore. In the
random and the other systematic, have
Dufas many as six a:re needed elsewhere
past five y_ears plans for operations in
&een tried· in the layout of the forestry­
(see Figure 2). Where the valley is nar­
this old growth Douglas fir forest have
logging plan. · The random pattern, in­
been prepared for initial and reserve
row 3.nd steep, few levels are required.
cluding about 29 miles of road, was laid
settings on about 8800 acres, including a
As the valley widens, more road levels
out in 1949 and 1950 for 3273 acres on
road system of 71.6 miles. In the stag­
are needed, and a climbing road must be
the south side of Lookout creek, shown
gered-setting pattern of clear cuts, more
added to start each level. When the val­
in Figure 1. Using the best prevailing
than 78 million board feet haYe been
ley narrows again, extra levels must end
practice, road locators took advantage of
sold;· 27 miles of road have been con­
to preserve efficient spacing. By keeping
a very thorough knowledge of the ground
tracted or constructed, and 44 miles of
in mind that climbing roads create most
al)d based the plan on economic yarding
additional road have been located in re­ -distances and good watershed manage­
of the inefficient
ileage, the art of de­
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More Efficient Road Patterns for a Douglas Fir Drainage I
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clear cuts followed the staggered-setting
or fo ur mites per sectio . A sampling of ',
·system of cutting.and external yarding 60 external yarding.distances. over· both
. distances averaged slightly less than 700
study areas indicates that the average "
_feet_<;>µ_ bo _ _ -a_r s. -:Eacli ai;e a ranges in_ roa_d sp_acing_ i
68:f t,, o_r_ -:��-r_t}(9_n e· l _ -i:
D eSigning an Efficienl Pallern
elevation from about 1500 feet to 450-0
quarter mile. Thus, 4.16 miles aersection
The 1951 plan for a systematic r oad · ·feet with about eqnaFproportions of difwould be the theoretical minimum.-Actu­
pattern on the H. J. Andrews Experificult roadbuilding topography.
. ally,_ the sysfematic pattern h.S O.!H-inile
. The areas are not strictly com arable
mental Forest was p epared on a topomore road-than the minimum. The.-differ­
ence is a measure.of'the·e){fra _mileag :
graphic map for the entire area una.er
in -other respects. The south side a Lookneeded' for connecting_ roads-1 Iandirig
management. As a first step we located
put creek has a larger area of high elevaspurs, and all' forms of topographic ob­
the theoretical minimum number of road
tions and l onger continuous slopes. The
stacl:s. The !es fliciei:! random
. levels required for efficient timber har- .north side has a major tributary and more
ttern
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-:_. 'vesting over·a complete rotation;-Jnstea - d- :,. ··com:pli-cated Stream -pattem>To--some' ex>· - ·r-equired- -1..43--mrles- more:',t-Oac!:-tl'lah>t}W,
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minimwn.
of _the usual procedure of trying one
t_ent, these _ topographic differences are
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lengthy road location after another, we - compensating,. but they cannot be eV hi
Amount of road - · constructed and--·
. ated. The layout crew's gradual accumumarked short dashes on the map to indi- ·
acreage clear rut , though not yarc:ISHcks
cate the best available road location at. lation of experience is another factor of road efficiency, indicate initial road
e·conomic int rvals from stream to ridge­
whi_ch cannot-be measured._
I,
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nt :_.1:1: ds _·in.. :t;he -ea·sqi es. ·
·rop. ·These marks- were ·made• at fairly ' .>,Ncr direct' cost coiripiirison5 ate avail-' ADciut i:v/o milesof toad were tecjuited
regular intervals on every main slope,
able. But a careful study of the two lay­
per section. This mileage figure was re­
proceeding from the lower end of the· outs, Figures r and 2, has shown.· fewer
markably consistent from sale to sale
drainage to the headwaters.
climbing roads,. and a higher proportion
even though total road mileage and cre­
Control points such as saddles, good of well-spaced road levels on the. north· age clear cut per se ction wi;re redu ced in
stream crossings, critical landing_ areas,_ ·sid . -Furthermore, afI: evaluation of road .later sales. Acreage clear 91t was reduced
and switchback locations were also des­ •density, yarding distances, and gradients
to leave wider units of green timber be­
ignated. When the initial marking was indicate s that real advantages have re­
tween clear-cut settings for fire protec­
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·complete, we connected dashed lines of suited from· a· systematic approach.
tion.
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about eqtial_elevation toform a series of, :· Pro_!>a Iy-th::-i;r.e>:te_st._galri from this
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road segments that roughly paratleled ·.··systematic pattern IS m total road mileage. ()pfunum:Ya r mg·Drstances
each·other on level or descending grad e s. :per square mile of layout--0.62 mile less
Anoilier measure of efficiency is theef­
The best of several map trials using this road per section than· the early layout.
feet of road pattern on yarding distance.
procedure was chosen as a basis for the A better measure t>f efficiency is to com- Variation in road spacing fron1 the exact
systematic pattern of the 1951 plan.
p r each pattern with the theoretical
"econ ?rriic inte.rval" '\vould be
. a sensitive
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of road. On flat land,
mm1mum denS1ty
yardstKk but difficult to opt m. Actually,
.Climbing roads were added as ·a secfor. examp e, a quarter-mile _ spacing
good roa:I locations are hm1ted,. and ?Se
and step. Three techniques were used to
of an optimum range of external yardmg
minimize the proportion of climbing would reqmre one road through each 40,
roads. ·First, maximum . allowable grades
generally were used on climbing roads.
Second, road levels already on favorable
grades were u sed wherever possible to
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gain elevation. Lastly, the most gentle
topography between toad levels was used
for climbing roads; t4is technique min­
imized differences in elevation and re­
duced the length of climbing road re­
quired.
The pattern could not be applied in­
flexibly to every part of the forest. Occa­
sionally other considerations conflicted
with the most efficient pattern for log­
ging. Expensive road construction, topo­
graphic obstacles, bridge locations, water­
shed protection, _ special yarding prob­
lems due to topography, the neea for
good landings, and the need for more
direct routes for large timber volumes .
all sometimes called for more roads than ,
were needed for timber harvesting alone.·
By using the systematic pattern as a yardstick of minimum road length, however,
MCRAE
we could evaluate costs rather precisely
in deciding how much extra. road to
LEGEND
build.
signing an effiCient road pattern, then,
becomes largely a matter ot judgment in
starting and ending road levels.
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Comparison of Old, New Patterns
A good comparison of the two road
patterns in many respects is provided by.
the south and nortfi sides of Lookout
creek . The same men planned both lay­
outs. Similar objectives of forest and
water5hed management were used. All
Present Roods
,
Reserve Setting Roods
Projected Roods
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Present Cutovers
FIGURE 1 -Earlier layout on south side of Lookout Creek used random pattern. Steep
gf.ades are prevalent, road density higher, yarding coverage poorer than in later pattern.
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fore 1951, an<l in the 4 to 890 class later.
Still the b
aradient data indicate a niorc
efficient plan through a systematic ap­
proach. First, it provided 10.% more o
light fayorable grades .(0 to 4% ) . Sec­
ond, less road \Vas required per square
n1ile eYen though lo-..vcr ·grades "·ere
·used.
This trial has shO\\'n an1ong other
things that chinging maximum grade
standards may have relatively llttle effect
on road density. 1\'[ost of a ro:.id p:ittern in
any-drainage co 1ld conceivably be dev l­
oped with parallel
_ roads on leY l or gent­
ly descending _grades. _Such roads are
inostly unaffecte_d by changes in grade
standard; but climbing roads, which
make up a smaller share of the total mile­
age, are strongly affected.
In this trial,
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climbing ioads, those \vhose purpose is
to climb between levels, ·accounted for
only 19.2% of the road system. If a 10%
rather than a 7% maximum grade stand­
ard had been used for every climbing
road, the entire savings '\VOuld have
atnounted to only 0.28 miles per section,
or 5.7% of the present road system. But
not all this possible saving could have_
been realized. About 49% of the climb­
ing roads are located on steeper than
standard inaximum grade to avoid ob­
stacles. Others vere marked on the only
feasible location.
The study also emphasizes the difficul­
ty in eli1ninating steep favorable and ad­
verse gradients. In spite of the de ire to
avoid then1, 14% of the syste1natic pat­
tern is in favorable grades in excess of
8% and 9.3l/'o in adverse grades, mostly
under 4%. The proportion of adverse
grades remained about the same in both
the random and systematic _ layouts.
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Present Roods
Reserve Setting Roods
Projected· Roods
Present Cutovers
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FIGURE 2
Systematic road pattern was used on north side of Lookout Cr:ek. Road.
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levels are distinct, climbing road minimized. Road density is reduced, yarding improved.
distances as an index of spacing is easier
and more practical. Within -optimum
range, costs are considered nonnal; out­
side this range total costs of yarding and
roadbuilding increase rapidly.
In 1949, V.'e estimated from earlier
studies and local experience that this op­
timum yarding distance rariged betv:een
400 and 900 feet for highlead and 500
and 1400 feet for tractors. These li1nits
have been roughly verified from time to
time, using yarding and road costs from
the experimental forest. The computa­
tions have produced figures for optimum
road spacing ranging from 980 to 1600
feet, depending upon equipment, spac­
ing of landings, road costs, and stand
volume.
Using 400 to 900 feet as optimum
range for yarding, we found that the sys­
tematic pattern reduced the area outside
optimum by nearly one-half-from 83.4
acres per section to 49.2 acres per section.
Most of this !eduction was in external
yarding distances of less than 400 feet.
A primary source of short yarding is to
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landings along climbing roads, wh1ch
were greatly restricted in the systematic
road pattern. Overly long yarding also
was reduced, mainly because improved
spacing of roads provided a more uni­
form spacing of landings.
How would additional reductions in
road density affect yarding distance? The
only answer available is from a 3700acre tract in which road densities were
reduced to 4.82 miles per section. Here
the area requiring external yarding dis­
tance more than 900 feet rose again-to
nearly 20 acres per section. Thus, it ap­
pears that under a systematic pattern a
reduction of road density to less than
five miles per section inay only result in
longer yarding distances.
A third advantage of the systematic
road pattern is ·a inarked reduction in
road grades exceeding 8% and a corre­
sponding increase in the 0 to 4% and 4
to 8% gradients. Unfortunately the com­
parison of road grades between the sys­
tematic and random patter s is not as
straightforward as other measures of
road efficiency. Maximum sustained
grade allowed in early layouts was 10%.
The regionwide forest service standard
was changed in 1951 to 7% sustained
maximum. The new standards were fol­
lowed in the systematic plan so that . the
new roads would qualify for permanent
maintenance. Since climbing roads make
up a high share of any road system in
steep topography, naturally most roads
were in the 8 to 12% gradient class be­
a.
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The Forestry-Logging Plan
One of the more important by-prod­
ucts of systematic development of road
patterns has been its usefulness in design
of the staggered setting. Earlier work aimed for a somewhat cirrular setting v.rith a landing in the center to minimize yarding costs. This type of setting often presented problems in finding good foe _
lines for slash burning. In add1t1on,
c.
d.
FIGURE 3
Four road patterns: A-Random development; B-Switchbacks at regular
intervals from lowest road; C-Regularly spaced roads climbing in direction of lowest
road; D-Single climbing road with ot ers on levels roughly parallel to valley bottom road.
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windfall and tre.es..which died on the up­
per and lower edges could not be effi­
ciently salvaged without yarding lbrough
the setting and damaging the new ,crop
,
of -young trees.
More recent forestry-logging plans
v:ith a systematic road pattern have used
settings where a strip or patch is cut out
between road levels. This type of cutting
unit pennits use of roads for upper and
lo\vcr boundaries and orients side boun­
·daries at right angles to the contour. All
such boundaries make good fire lines.
Windfall and mortality losses along the
borders either occur along the roidS or
can be yarded straight up or down the
cutting lines without: uridue disturbance
within the setting. Furthermore, all fu­
ture woi:k, such as planting, thinning, or
pruning, is ade easier. M.en and· equip­
ment can be hauled.to the top so that all
work can progress d_ownhill.
Extra c_osts in rigging up are the maiii
disadvantage of this type of setting. In­
stead .of "full tree5" to log the entire.
yarding circle, the newer cutting unit.-f. ­
quires rigging "half trees: for yarding
either above or below . t he road. .Afi;\>, the
new type of unit may require. a slightly
higher initial road cost per thousand
boar& feet harvested: However, . total
road-mileage per· square inile. is· approxi­
mately the same for both types of unit
Thus, besides being more efficient for
logging, the systematic road pattern has
silvicultural advantages. The pattern has
greatly influenced forestry planning on
the experimental forest. The general
principles may be useful on other forest
properties.
Reprinted from
Leading Timber Industry Journal
PORTLAND, OREGON. Vol. LVI, No. 6
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April, 1955 .
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