Modeling Low-Volume Road Erosion
Lowvolume roads a r e m v g n i d as oneof thephayaolurrs of xdion the
men1 m m y watersheds. ?bc ~ l l k m
ham canied out
-1s
of the oompler soil a s i o n pesses occuuing on low-volume
man years'Anm-ew of wiresearch sumwim
IhG results of numcxous past and ongoing field and computer m-ng
and effects of road designon load
snrdieson mad
meauthorshamfound e b l m i n e a n d -lmhecffmts on
&are
oiim washadowcd by heeffe&oi.nnting. ~ & & i lnosion
on mads is from corlfenmcd flow in ruts a dilches. Adding gravel
i n c ~ h Y ~ ~ n d ~U ~~ c~ er Ys ~R od e nm s.b * m f ~
canalso bedEdcsvdbyrrducio~h~orhyremovingroadc.m
au~orsare&velopingapphtior~softhe WaterErosionRediaianFmjst model as u9cT9cTfdmm.
for mad maOagBTS,
of
Fdw
work is required to
m
arcchniqucs on WaKr quali* and to develop new low-impact road design
and management technology.
''
Lowvolume roads generally have a native soil surface or a graveled
surface.FnqUMrly ther are 'ocaIed in wateFSheds in which the OaturalraasOfemsion
fromDngelandorforestsare
low and
where erosion ram from apricultd activities are z c n d l y lower
than from a road. ?he threedominanteffects of m a g o n the in*men1 are alteration of watershed runoff characrcnsrics, mass wasting,
and surface erosion. Mmentarion of streams is panicularly serious
in uplandareas where salmonid gpeciesrequire gravel-coveredswam
Woms for spawning. Sedimentationcan also shorten the lives of
~eservoirsand watersupply systans relying on surface s o u m for
quality water for domestrcand ~ndusuialuses. Peak discharges may
be altered in basins followingroad consuuco'on. In watersheds with
hi& infiltration canaciw and where hillslooe flow is dominantlv
subsurface, roads have the potential to increase surfscenmoff and
intercept subsurface flow (1). Changing the hydrologic properties
of a watershed will often change the upland stream sedimentation
prwesses and advemly affect downstream structures, such as
reservoirs. brides. and other fearurnss in the stream's Roodolain.
In steep larain, where the climate may lead to saturated road
prisms. slope stability failures may lead to greater dimentation in
streams than surface erosion (2-4). In many cases, the sediment
pardcle sizes from stahiliq failures may be much larger than from
surface erosion and may include rocks and b o u l h larger than 1 m
in diameter.
-
-
-
ROAD EROSION AND SEDIMENTATION
PROCESSES
management (Figure 1). On roads. the construction, maintenante.
and level of traftic all affect the erosion me.
A number of components makeup aroad, and the design and management of each component may M u m c e the erosion oftheroad or
delivery of s u l i fmmthe road to a stream system. Figure 2 presents ffie main mad components that affect soil erosion The deslgn
and management of a road determine the flow path lhat water follows
to exit the road. All roads are designed to have a compacted foundation and to shed water. he main &oscsectional shapes of roads are
e r o m insloping, or outslopmg (Figure 2). On some forest roads,
ffimisalw asetdiitanceinwaferbarspaciogalong thelraveled way
to limit erosion. In addition, a mad designer can choose m add gravel.
asphalt, or ConCrete to the ~~rfaCe.
Designers may also consider
methods to limlt emion from theroad.Nlfacemnoff, such asadding
gravel to road ditches or specifying that cros drains deliver water to
convex slopes. where the water wiudisskpateoverthe surface mstead
of incising a channel. Road erosion rates are influenced by the flow
path that wrfaee runoff follows along the road(5.6)and the hydreulic
conductivity and soil erodibility of the road (7.8).
Path
The flow path length across the waveled way dependc on the shape
of the road and the presence of wheel ruts. The minrmum flow path
occurs on a smooth road with a uniform cmss slope. In this perfect
geometv condition the flow path length increases with ~ncreasing
mad grade and d m a s e s with increasing moss slope (4.Because
cross slopes are rarely more than 4percen1, a road 4 m w~dewill
rarely have a flow path lengtb less thanabout 7 m for road grades of
5 percent or more. If the road receives heavy traffic. espedally in
w a weather. ruts will form in the road. and emdmg water will follow the ruts instead of being divmed to the inside or outside of the
road. Witha ~ttedtraveledway, any benefitsfrom the milla1 design
shspc are lost. Even without a lulled traveled way, a? wheel tracks
begin to flatten. the cross slope the path length mcreanes until it 1s
equal to the spacing between any surface structures thin diven the
water from the road (61.
. . These diversion strucrureq mav be called
cross drams. water bas. or broad-based dim. Fieure 3 shows the
typical effects of flow path length on road surface erosion as predicted hg the Water Erosion Pred~ctlonProject (WEPF') soil erosion
model for a Lufkin. @%as, climate.
. -
Insloping Versus Onislooping Roads
Soil erosion and sedimentation are the products of complex intqactions among soils, climate, K ~ h yand, s u d a ~ vore ~
Debam wntinue about w M e r insloped or outsloped mads are
W h .Pqmmpolrcntfof inslopdmads point m the benefil of controlW. J. Elliol and R. B. ~ I Q Soil
, md Wsfar.Engiwaiq. Rwky Mounfain
Iingthc wafer inadifchwith planned ourlets under the running surResearch Starian. USDA Pons1 Savios 1221 S o h Ma* Morow. ID
face. Erosion in rheditcham be minimized by lintng the ditch with
83842.C. H.L% Waaabd Roccnaco. Roelg MamtninSlation.
USDA Faw Service. 316 EaJt Mynk SarL Boise. ID 83792.
nonerodible rock The beneh of outsloping is d~spenedBow, but
&aduri~g \uu~Oo?didori&kidaird~onlhe[2Jstat&&atth%
m i wf
is pdmb!y the ~
$M a r a&xingd~
m9nr:gWlWcsl- cOmp%tbgC seaimcnf p a r m m t i o n
2 .$am
f o ~ en
iWW midWWr# On which the mafit B
M was h & r g t
r*g
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~ ~ ~ . . ~ p ~ { ~ S ) ~ ~ a ~ ~ a f 5 ~ ~ . g
intemp&&i;wfor a;w&:~aa&2ds$~m.&~wgks:anrl&
( I . ~ ~ , ~ ~ W W K @ J ~ wltea,
& ~urn. ~ I ~ ~ ~ £ S
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8
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on
~ l L ~ a ~ ~ B , i ~ a ~ , , & ~ w ~way~ a r , d
w;&-bnpwefm&q
@.@@=;*
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i e s be
.mw
. . . . ~.&W,%W?%T%Bis@& by WI alh=iw
&w
~ ,~.~; i i. t @
.
& ~ ~ g ~ n iuky
, -have
q :fo*d.
~r@,~~~
.
&&+;&w...
.at:he.tizpnr~.of W U ~ Ffl~whpaw&ei
,&&
stope (lo).E . & d h : & w & . w i ~ e d & - *
I&tle.Merrn.nh w thc~&%i~:tua~e
mm,-k.ihai
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8
1
a
W smtfq,s,@gJ$;
!&~I@@;:*>M
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shspedepcnds an &s,w<m&{i*w~Mh9.
w*
\&y &&
I
k!& SE.3 tuntrinp surfncfand
~ ~ k ~ ~ ~ m a f ~ i t ~ - @ f ~ m a f o ~onhheffee1r
1~ye@'r1udy
dWiht@h:b-B?wm~@ex
bm. mad:&e. ldnd cutsIope Ireigk~
w&t@~refio~,olenrirrmad?rim.
~bwwarionnfrom?4
g)~isii~b;i&
@p&on,Cu@R ~ ~ ~ E + W
!hatEthe
U cnnd11ion.ol
the dilclr
is mi&^ detWs@t @@itnwtpr&Mion in the fifirsiyew
aPter.c~Wkr?; f~lid.a$$@~i..sil~:~t&nRhip'betureeu.~e
&&&;wa:&h.&,wm&
by ma&&&&
&w@p~~~~#$m&.i.T~gw
etd.(;l$a-%nd
rhat if w
d
g are wellaainraiL&ed;the,A.aip~& $d o a b ,a . W
piismis in.*ditFh ( F ' i 4% @il+@tch
.i.~.mdW.&Ma
.&F-*,
r&.&meme~ pmau&$&fi:gildw ; p w b ft&xluan,of&&
gt.a@int
tltesegmar Wth, Wig& tM.nave W n shown IO
mmiw well in B wsion smd&~:(~~,,~.~..
Fio dktiddshil, was
p t o ~ ~ e M v ~ ~ d f ~ e%3Sfie:@Uo0pc:E~Eni@n
~tioig,
&m~tatciid,m1w~~:~&18,tr
~ $ ~ m ,
Q s~e &
d~
h pX ~ a n & c~ u r & ~ : ~h e MffFXs.
~ t . .~~
a e f * main *&,m.qm
&$ m e . - & !
&,,,Botg
&
with ;wwety &mdwwi&~m:
*west &at eurdope cwdition
wt and the thr.raad surface is in gm&gmn&thp! nxky ha~cratte
wighi b o ~ n edwnintwi
.
after mme wvq,nmsily [hroltgh !he
the W h .
e ~ l G F c W g p e ~W~e ,ns ~ li 1~a W l i i @wdily
f
erodedfiedi*nt gfi g . l i . . , q m e&&&@@I &adindin
C
o
~
~ Flow
e Erosim
n ~
e0notaW flow c a m nw%:@.iMt
pgj *d.ditohs
61e&,
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*hecl,mrs,w
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my&&. &i*'i&
e~~
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. ,.
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&&vc*
48JfiETu~ing'@&W@&,*
@I@$Q@uW&
2'
En
Plan
F
raa.ds is much lower
agrictilNral sdflq
FIOarae.9 Typkal
ms@$a~
p
~
&:tfaw p&thleqafh sbdpeccmtroad grpmwton mad
w
i
@
~
m
~
and forest soils (9,%,21). The h y W l c conducuvity of vad@
forest conditions b&own in f i3. ThecmWcIivity varies from
I & & ~ J lmndhforaMtivi?-s~orltongravaledroad~omore
I
t h a n 8 0 d ~ a n ~ f o r c s t T h e s e d i ~ a r p m
agement eIT6ts that tend to ow&adov effects caused by differin soils. TbE&u%mncs
of large ~ m 0 1 m I s o f v ~ t ian8
o n fa&
liner is m p m i i l e far The high i n f d t d o n capacity of w n d l s h d
faesc soilk Ra& ace h ' l y compacted. resulting in near-zao
conductivities on all soils.
LwewiiCundy (221 showed that roads without gravel have concktivities in the range ofO. I 100.5 mm/h wlureaq roads with gravel
have conductivitiesin the range of 3 mmlh (9.21). The m5ulI is a significant diffeienceinm f f anderasion naes, espiaLIy hc l i
Which
Ofthe
& ffOm snowin''. Swwrneltnrcsape
less than &all
(23).
in 18~5
r~off.
T&k 1 P W ~ W
the diffwllce in mad runoff and sediment yield causedby this diff e m c e in conductivity for a snawmeit-dominated dimace in the
Unitcd States m d a Was c l i m e Mth little snow. Grs~dm the
wnhUnited States mbces predicted emion by mmo than
80 percent, aeommonly wept& @ w h y fee.! p h e w . w h e m
hTexas the model
That a m a t e surfwing reduces road
erosion by abut 35 percent.
'
miw
To determinethe roleafsoil p r o p e ~ e on
s mad cmdibility, aseries
-of s t u d i ~was initiated to collect F ~ l ddata from a wide range
of native-surfaced mads. From these studies several researchers
18.24.2n
. . determined that on natixe-surfaced roads. the inlerrill
erodibility is similar to that of cmpland soils, the rill cmdibility is
similar to that o f ~ e 1 a n d s o i l s .add thecmductivlty a near zero.
Typibl values &re presented in Table 2.
..
MlnCAnON
R m c a n y i n g out this project have bccll active in researching road erosion mitigation tcehmquw. These techniques include
tiTepE-,
-accplBeement.
road closun,and rod
mainUXTance.
kedaeed Thre Premzm
In a 3-yw study in the United States in the b a d e Mountains in
Fola (261f
r
m
d that sediment production was reduced by
FIGURE 4 Sw- of sediment frum ieslopimgroad template @redieted
sediment M d in kgly fmm 60-m-long road .wment) (17).
Forest
I
Hydfallc Conductivity (mmlh)
FIGURES Typical hydnulir mnducfivities for roads compared wifh other soils l7.8,12,21l.
on all axles, and by 80 percent when tire pressures were reduced to
480 kPa on the steering axles and 210 kPaot 340 kPa on all other
axlcs (Table 3). Foltz and E l l i 1271
~ observed on the swdy site rhat
reduced tkpressures resnltedinlessrurformation. Wlth leu rutting.
water tended10 tun over the edge8 of the road, instead of accumulating in flow directly down the ruts, which eaused ennion from concentrated Row. Forest managers have accepted these results. and
some timbersale contracts in central Idaho now include reduced rue
pressnres a? one of the methods to reduce mad emqion Other benefits of operatingar reduced Cue pressures include longer hauling scasons, increased vehicle mobility, derreawd t ~ c maintenance,
k
and
improved operator comfort (28).
ro.rd by 95 percell!. S~vlft129) fouttd illat the thickt~cssof aggregate was mmportant. A SO-111111deprh provrded no mrtgatton.
whereaa a 200-mm depth pro\ ided 97 percem mitigation. Neither
of these studies was performed in the presence of traffic.For many
years forests adopted these rnitigatioil valum wifh lmnle considerauon of aggregate qualtty or tr~?ffic..Foltza;nd Truehe (30),uslng
loadedlogging t ~ c traffic.
k
found that the quality of aggregate has
an important effect on road soil eronion rates. An aggregate of
marginalquality allowed eroclon rate\ o f 4 to 17 timesgreater than
did an amregare of sood qmlity. The range depended on traffic
and precipitation.
nd Ellio~(271 believe that the differences
are caused by t h e f f e c t s observed for tire pressure impacts
and gravel addttton. namely conduct~wtyfind the presence of mts.
Aggregate Qualify
Read Obtiteration
Blmoughs and Klng (161 reported that I ~mm
O of good qudlng
aggregate reduced sedlment production from a graniuc surface
The off-site impacts of altcrzd runoff hydrographs and increased
sedimentation have lead to the panial or complete removal of roads
a* a frequent practice in U.S. Depmlnent of A-miculture (USDA)
Forest Service watershed restoration. There id. however. limited
research data to suppcn ohliteralion dccicions. One practice assoc~atedwith raadobliteralion is to rip the road with tinesmounted on
the back of a large crawler tractor. In o recent study on the effectivenessof npping. Luce (31)found that road conductivity inumed
From 0 to 4 mmfh before ripping to 20 to 40 m m h after The
~ n i ~ r o v m eis
n tmodest com~aredwith existing
- forest conduct~vities (Figure 5). but may lead to a substantial reductton in runoff in
climates dominated by snowmelt and low-mlens~typreclpitahon.
Although the initial ripping yielded ~nfiltrationcapacities similar to
forel soils,subsidence,co~otldation.and surface s d m g reduced
capaciti~to thesemadesf results. Soil amendments, such as straw.
may i q w e pufmnmce. The long-tern1 chawe in Ihe conductivtty ofs.doscdsoad has not been measured, although in many cases,
madssvmtuallytwomr ccuqetated leading to a mare natural infilrration me. The oomlidaced soik however, may take many yeam
to mw!ta a natural statc,if they ever do. Elliot el al. (32) observed
that iweascd conductivity may lead to an increased likelihood
of the mad prism becommng saturated. resulting in an increased risk
of failure from mmability.
45 percent when tire presuies were reduced from 620 kPato480 LPa
TABLE 1 Impad of Gmvcling on Road R u n o % dErosion for
Road 60 m Langand 4 m Wide with 12Porcent Slope, Predicted
with WEPP Model
Climate
Deadwood Dam,ldsho
Avnagc Amwal P&p (mm)
Lufktn, T m s
822
it16
Native Surface
4M
84 1
Oravd Svrface
78
R m f f (mm)
sediment Y~eid(kg)
Native Swfesc
2312
%I2
Grevel Surfaa
421
2468
ZUNSPORTAAnONRESWLRCH RECORD 1652
TABLE2 Typirpl WEPPEmmWrtyP~VploesforRore6tRo.ds
Soil
CleyLoam
Sift Lmm
Sandy
Gravelly
Oravclly
Loam
Loam
Sand
Onrvel%
20
5
5
60
80
Ssnd %
M
30
60
40
70
Silt
%
40
55
35
40
25
Clay %
90
IS
5
2U
5
Conducrinty
6.3
a3
1.0
2.0
3.0
ldlh
3eO6
Zd)6
Id16
2s06
O.WOZ
1) O W 6
00004
0.0003
0 W03
nmRn
Iararill edibility
kg-dm4
RiU edibility
s/m
forest &or buffer sVips. A number of templates have bea dm&
opd fm t8e WEPP moael to aid in fnld -1,lioarims (9). USDA
W d r e s o r e~q u i r e ~ ~ ~ h t o a i d ~ i n ~ ~ t h gBmSt
t h e Ssrviw mseaich is mmmitted m develop applications of
envimnrpcnfal impaeis of vadous ~ B D ~ ~ QenR the
S design and nmW6PP to mote fully ewiuete the impaee of surrent ot. proposwl
agement of forest roads. M~uncmussoil d o n and road Sability
badm mane gem em andmhigation pnmicts.
modal8 have bstn devdoped tomisr designsw and mawgees The
several w & ~ : t t m b e c n h c l dWmb more rhao 1M)USDA
aUm0~"
-in
enosianmaaetingis&~&ndhnd
Forest'Savicepm.~nnel,onthe a p p l i of & WEPP model to
based on theWEPP model U2.13X
E w t ccu&tfo&. Because most pahe& u r n of WEP arc &~ ~ . f i ~ c O u iid.terfaCe,th~amhwe
& x
hamfocusedonsim-
Lms for Read Seetioos 61 m Lmgwith 12 Paemt
Grsdientr (Average (mm 3 Yca1'6) (26)
The X-DRAm' aorilputer program ie bssed on a m d y by Modn
bf L (33,in whirl?a database wn5 &ve@d of mOre lhan 50,000
WEPPnrns an road scenariosthatineluc$d an eroding road surfgee
and WIope and a dcpositwn amg bmvem themad and thenearesl
s a a m . The d t s of rhis ~tudyare accwstd by a usw-friendly
interface osRcd X-DRAIN. For a given dimate. smi, and topopahie tondhion. the. X-DRAIN prog~mpresents the &dim-t
&livuy fw20eonlliin&w af&gr&m~aud warcrbarspaeiqg
valw. Elliot et d.(34)describe how to qply this b.& coniigunitiQntog ange of %Id Conditibm.
C%@W:@@@@tWeW31F t l d e s cnntinuing theroad toPogar
bt@sWiy in OrrgM(P?), deMwing a model
w i . I ~ . ~ & m I P e ,l " YmUT&
;
t
&
+
~
o
b
~
08
q
&on
u
~
&bs, and &doping
&wb
.. . . . . . P
~ P w and~ ~ B & ~ ~ asdaidss
fWt mad dks&'&g l@m&meq~
. phy 9n&-
Atem chm my'= huther wearch Indude the feII6wiq
To&
~
FWm ~TWkaKRcpdWIId-9..Int~DUou\in
WtMahdw
~ ~ : @ a t i m n , . U S E IFcrasr
A
Utsb. 1973. Sgp.
12. La&& l;M., W.la13lli D. C FBm&h, C. R. MeyB, a H M. A.
Neettbp WEPP-Pmiiaii, W d Erisivjn Using i Frksi-BilSld
Q aid maasgffs in eating priorities fw rogdr for main-
~
o
n
,
o
r
d
.
ceM.~an~O+l,
voi. 52,NO.a 1997.
Moaal..>m~a
l w l mrB
o0.061M.
~7,
13. Ranagsn. D. C, and L 1. Livingston. 1995. WEPP User Samnaty
US&!-Water tiosioq Plodicdm PmJeEI IWEPP). NSERL Repan 11.
USDA-ARS National Soil Emsion Ls6cntory. W a t Lafaynsr Ind..
.-,-.
,on<
14. Tysdal. L. B. EUin. C. Lue. andT. Black. Modelurg Insloping Road
Erosion Roatses with LCWEPP Watersbed ModeL Paper R5014.
Prucoted M 1997 ASAE lnternabnal Me&og, St. Joseph. Mich..
1997.14 00.
IS. F
a
1
6 R~~.~ediment
R d i n Rom RonscRcadtwit# Wssl Ruts.
Wflrcshcd Phnhiug m&.AneIw& & A
&.
.&$e,t3=urY&, 8.Y..
1%.
16.
E. R....:J and 1.$
~Ydn%..&E(ucn'~c
I.
&il .!&$&on Forcn.rR+Gcn~ral ~ h n ~ R ~ ~ - 2 6 4 . l ~ n t snri
a h F w & ~
&nge.~swch.Sra&qq
USDPI FWI S u u ' i : ~ d a iuug.19~9.
.
i?.
c.R.. n d T . X.
$&~*i:ph,dua,,frant,~~iww b
id %Wrm&eptir(.cmdaf r%vir~i3.R u + y M o 3 = a~m .~ ~
USDA &'ox-Service. Bbkse. W h ,1397;
'TB MeC&.B; R:.G. R.F~~.:e.K.MLtcbW,u,andL.
D.
=.BeS l o p z I j e a @ h W w f b r t h h ~ ' M-.-ion
I
, msao~imts
a f a s r w a , v o ~ . n . ws, 19w.pp
I.
+~I-I.~,
19. NeaxiwFd; k A ~ S i i t t C ~ ~ n u ~ F a o cforS1apeStwpe.w
rion
I&ewa on $?ilbss. Svit$N'.Aar. JwrqII.Vol.61. 1997,,m. 917-919.
Lgw, C. H Pmewfi B R .W~llpdB.Jn
~
Enaimm+trY,ralo&' @.S.
Ward andW, J. Elli,n,.&.:+.CRCRrra, kwis Publishen.NewYcrk.
t9.95,pp. 267.268.
21. Flurt!hw.G. PJ..and F . L W W & R Z d i e t i a g & f i l a a t i O n P ~ f b
a i%dWmenc M i . T ~ z e f f o m . e f t k&SAE
c
wi. %.No.. 6.
1987. ad. l?.OQ-17
.05.
22. ~ u a e . ' CH..and?. W. ~ m d y-P
.
IbtiWon fora Rmoff
Medal far For& Roads. W m Argcurces&semcIt, W43. No. 4.
+.
ma&.
J
a.
ISM
... ,,rC.m 1 097-1 MQ
23. SIMW &&/t!w: S I ~ ~ I I M&mm
+
cJ rb~
&ow In~sripziqns.U.S.
&my CMBsafthgiwrr~ ~ n h W f r e . Q i ~ s Orsg,,
' i n ,19%.
~~~
are^, psd E. @a&.
2.(. E ~ ~ . ' E : R . , . J c.H.
G.
& w i n g IUWI.
J?&fMUg af Ferw S d l r TmmWm @ r h c . W , V01.35. Ss.S,
1992. pp. 1.4s9-1 .w.
3. Dm%;P . , V . L O i W O R LUec E&&@&fNriU~&iIir).
far~7,nflmvcdEnlSi~'PtcdicfiDn
M&a
T&&l
Rcpaa of A g h s
--.-
~-~~
-,-- ~
Wallingford. O1Padabirr. UoitDd Kingdom. 1987. pp. 25933.
4. MOntgomay. D. R Roed Surface Drainage. Channcl Initinion, and
Slope Instability. W@er Resourns Rerrorrh. Vol. 30. No. 6. 1994.
~
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sou Ban@ RtSaar&
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1 9 ' U&,
-26.
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Ek, E S B . SEdimmt,Redactian Mh U s e of Laatera Fire
Pmssum-SG &W T ~ t s u c IJ~a ,d l af Cmmercid PdricJ~~.
ua.2%. I.@?.. 1w.pg. 376-31.
8.F a l t r l B.,
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Tire
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Fomr Ravd.dwl ;Wwd,Tmnsgen;8 I n P i a . m . Wesd &aW-
Lagging Rwdr lncermoukain F m s t &d Rangc
Expabacnt Station. USDA ForoslSewiez aden. Utah. 1977.42 pp.
6. Folrr. R. B. Traffic and Nc-Traffic on an APPIWU Surfaced Road:
r u a Organization. Rom. 19%.
28. G r n f i d b P. H. Ccnval Tire Inflation: USDA Fomsr Scrvicc Dcivlcp
mcnt Pmeram. P a m 937510. Resented at 1993 lnremarional Winex
~;~ecti&itheA&& st. lew.bmdt.,I=;
29. S%ii4 t.W..k..%il~
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7. 6iila.w. J..R"B.FoI~L,&~M.D. Rernboldl. PRd~c"ng Scdimmauon
IeMrng. VDI. 8. k.
4, 19844pp. .EOQ-ZS..
from Ro& at Sneam Omsings wiLh me WEPPModel. P e r 94751 1.
30. F o t a R. B.. and M. %be. E h c k ~ F S i g p @ f e Woa.Scdbin
f~y
Rerented a 1994 ASAE INCNIional Winter Meeting. Sr Joseph
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Dmin~ing~~YiddModrL96
1801Smr.TshnofoW
77
aad D e v e l o p m M C c n t a . U S D A ~S a v i a . S m ~ , C s l i l .1998.
.
TRANSPORTATION RESEARCH
RECORD
No. 1652
Volmne 2
Planning, Adminisftation, and
Environment; Design; Materials,
ConsW&'on, and Maintenance;
Operations and Safety
Seventh International
Conference on
Low-Volume Roads
1999
Papers presented at the Seventh International
CDnference on LowVdume Roads
May 23-26,1999
Baton Rouge, Louisiana
A peer-r&md publicafion offhe T~""sportation
Research Board
TRAN~PORTATION
RESEARCH
BOARD
NATIONAL ICESEARICH C O ~ C X L
NATIONAL ACADEMY PRESS
WASHINGTON, D.C. 1999