Park Road Std

7/28/2019 Park Road Std

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Pref ace

The pur pose of t hi s document i s t o meet t he need f or Nat i onal Par kServi ce r oad desi gn st andards t hat wi l l accommodat e cur r ent or pl annedpar k r oad use, whi l e cont i nui ng t o pr eserve t he nat ur al and cul t ur alval ues of Nat i onal Par k Syst em ar eas; t o addr ess t he r equi r ement s of St andar d 12 of t he Federal Hi ghway Saf et y Progr am St andards ( 23 CFR1230; 23 U. S. C. 402) ; and t o pr ovi de desi gn gui dance f or pr oj ect sunder t he Feder al Lands Hi ghways Pr ogr am f or Par k Roads and Par kways( P. L. 97- 424; 23 U. S. C. 204) compat i bl e wi t h Chapt er 3( C) ( 1) of t heFederal Hi ghway Admi ni st r at i on ( FHWA) Di r ect Feder al Manual . Thi sdocument i s al so i nt ended as a def i ni t i ve gui de f or manager s, pl anner sand desi gner s i nvol ved i n t he pl anni ng, desi gn and const r uct i on of park r oads.

As t he Senat e r epor t accompanyi ng t he Feder al - Ai d Hi ghway I mpr ovementAct of 1982 st at es, " Roads t hr ough ar eas admi ni st er ed by Federal l andmanagi ng agenci es must be car ef ul l y desi gned t o pr ot ect i mpor t ant

nat ur al and cul t ur al r esour ces under t he j ur i sdi ct i on of t hoseagenci es. Such r oads must be desi gned t o bl end i n wi t h t he nat ur all andscape. Because of t he r esour ces pr eser ved i n t he Federal l andmanagement ar eas, and t he t ype of t our i st use i n such ar eas, t he r oadsi n cer t ai n i nst ances do not have t o be const r uct ed t o normal hi ghwayst andar ds. "

The st andar ds cont ai ned herei n pr ovi de f l exi bi l i t y i n t he pl anni ng anddesi gn pr ocesses t o al l ow f or consi der at i on of var i at i ons i n t ypes andi nt ensi t i es of par k use, f or wi de di f f er ences i n t er r ai n and cl i mat i ccondi t i ons, and f or pr ot ect i on of nat ur al and cul t ur al r esour ces i n

Nat i onal Par k Syst em ar eas.

I t i s i mpor t ant t o not e t hat t he st andar ds var y consi der abl y wi t h t het ype of use t o be accommodat ed. Basi c deci si ons wi l l have t o be madeby par k management i n t he appl i cat i on of t hese st andar ds based oncar ef ul exami nat i ons of t he desi r ed use l evel s t o be al l owedconsi der i ng i mpact s on vi si t or use and r esour ce pr ot ect i on i nconf ormance wi t h l egi sl at i ve mandat es.

The cr i t er i a pr esent ed have been adapt ed f r om avai l abl e desi gnst andards t o meet t he uni que r equi r ement s of park r oads. Thi s wi l lpr ovi de a f r amewor k wi t hi n whi ch desi gn and const r uct i on of park r oadsshoul d be conduct ed; however , t hi s document i s not i nt ended t oencompass a l evel of det ai l comparabl e t o t hat nor mal l y f ound i ndesi gn manual s.

These st andar ds wi l l super cede t hose adopt ed by t he Servi ce i n 1968 asexi st i ng par k r oads ar e r econst r uct ed or when new r oads ar econst r uct ed. On r esur f aci ng, r est or at i on and r ehabi l i t at i on ( 3- R)pr oj ect s t hey wi l l be ut i l i zed t o t he ext ent pr act i cabl e and f easi bl e.


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Acknowl edgments

The 1983 Par k Road St andar ds Task For ce acknowl edges i t s i ndebt ednesst o t he Par k Roads Task For ce appoi nt ed by Nat i onal Par k Ser vi ceDi r ect or Geor ge B. Har t zog, J r . , i n 1967. I t s member s wer e AnselAdams, I r a Gabr i el son, J oseph Penf ol d, Char l es E. Kr ueger , Rober tLi nn, and Wi l l i am C. Ever har t , Chai r man.

The Par k Road St andar ds t hey compi l ed and publ i shed i n 1968 set downt he basi c phi l osophy of par k r oads whi ch had evol ved over many year ssi nce t he i ncept i on of Nat i onal Par ks. Thei r wor k pr ovi ded t hef oundat i on of our ef f or t s , and s i gni f i cant por t i ons of t hat ear l i erdocument , i n many i nst ances ver bat i m, have been r et ai ned i n t hi sdocument .

We al so acknowl edge our gr at i t ude t o t he Feder al Hi ghwayAdmi ni st r at i on, U. S. Depar t ment of Tr anspor t at i on, whose t echni calassi st ance and advi ce have been i nval uab1e- - par t i cu1ar1y t hat of

Messr s. Thomas 0. Edi ck, Ot t o Mayr , Norman W. Loef f l er , Rober t War r enand W. Lar r y Kl ockent eger .

Fi nal l y, we ar e i ndebt ed t o t he many NPS and FHWA empl oyees who, overt he year s, pi oneer ed an i nt er nat i onal l y recogni zed t r adi t i on of excel l ence i n t he desi gn and const r uct i on of par k r oads and parkways.

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Par t i ci pant s i n 1983 Par k Road St andards Task For ce:

J i m J . St r aughan, Ci vi l Engi neer , Denver Servi ce Cent er ,Chai r man

Rober t R. J acobsen, Super i nt endent , Shenandoah Nat i onal Par kMerr i ck Smi t h, Landscape Ar chi t ect , Denver Servi ce Cent erDonal d A. Fal vey, Ci vi l Engi neer , Rocky Mount ai n Regi on

J er al d M. Lor enz, Landscape Ar chi t ect , Denver Servi ce Cent erGeor ge Wal voor t , Ci vi l Engi neer , Nat i onal Capi t al Regi on

J ohn Si ngl es, WASO Mai nt enance Di vi si on


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Tabl e of Content sPage

Pr ef ace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iAcknowl edgment s . . . . . . . . . . . . . . . . . . . . . . . . . . i i

- - - - - - - - - -

THE PURPOSE OF PARK ROADS . . . . . . . . . . . . . . . . . . . . . 1

FUNCTI ONAL CLASSI FI CATI ONS OF PARK ROADS . . . . . . . . . . . . . 3Park Road Syst em . . . . . . . . . . . . . . . . . . . . . . . . 3

Publ i c Use Par k Road . . . . . . . . . . . . . . . . . . . . 3Pr i nci pal Par k Road/ Rur al Par kway . . . . . . . . . . . . 3Connect or Par k Road . . . . . . . . . . . . . . . . . . . 3Speci al Pur pose Par k Road . . . . . . . . . . . . . . . . 3Pr i mi t i ve Par k Road . . . . . . . . . . . . . . . . . . . 4

Admi ni st r at i ve Par k Roads . . . . . . . . . . . . . . . . . . 4

Admi ni st r at i ve Access Road . . . . . . . . . . . . . . . . 4Rest r i ct ed Road . . . . . . . . . . . . . . . . . . . . . 4

Ur ban Par kways & Ci t y St r eet s . . . . . . . . . . . . . . . . 4Ur ban Par kway . . . . . . . . . . . . . . . . . . . . . . 4Ci t y St r eet . . . . . . . . . . . . . . . . . . . . . . . 4

FUNDAMENTAL CONSI DERATI ONS I N PARK ROAD DESI GN . . . . . . . . . . 7

PARK ROAD DESI GN STANDARDS . . . . . . . . . . . . . . . . . . . . 11Desi gn Cont rol s & Cri t er i a . . . . . . . . . . . . . . . . . . . 12

Desi gn Vol ume . . . . . . . . . . . . . . . . . . . . . . . . 12

Desi gn Speed . . . . . . . . . . . . . . . . . . . . . . . . 12Desi gn Vehi cl e . . . . . . . . . . . . . . . . . . . . . . . 13I nt er - Rel at i onshi p of Desi gn Cont r ol s . . . . . . . . . . . . 14

Desi gn El ement s . . . . . . . . . . . . . . . . . . . . . . . . 18Ver t i cal Al i gnment . . . . . . . . . . . . . . . . . . . . . 18

Gr ades . . . . . . . . . . . . . . . . . . . . . . . . . . 18Ver t i cal Cur ves . . . . . . . . . . . . . . . . . . . . . 19Gener al Consi der at i ons . . . . . . . . . . . . . . . . . . 21

Hor i zont al Al i gnment . . . . . . . . . . . . . . . . . . . . 21Maxi mum Degr ee of Cur vat ur e . . . . . . . . . . . . . . . 22Super el evat i on Runof f & Tr ansi t i on Cur ves . . . . . . . . 23Gener al Cont r ol s . . . . . . . . . . . . . . . . . . . . . 23

Si ght Di st ance . . . . . . . . . . . . . . . . . . . . . . . 24St oppi ng Si ght Di st ance . . . . . . . . . . . . . . . . . 24Passi ng Si ght Di st ance . . . . . . . . . . . . . . . . . . 26I nt er sect i on Si ght Di st ance . . . . . . . . . . . . . . . 26

I nt er sect i ons . . . . . . . . . . . . . . . . . . . . . . . . 27Number of Lanes . . . . . . . . . . . . . . . . . . . . . . . 28Cr oss- Sect i on . . . . . . . . . . . . . . . . . . . . . . . . 28Recr eat i on Ar eas . . . . . . . . . . . . . . . . . . . . . . 31Sur f ace Cr own . . . . . . . . . . . . . . . . . . . . . . . . 31


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Roadsi de Sl opes & Dr ai nage . . . . . . . . . . . . . . . . . 32Guar dr ai l / Gui der ai l . . . . . . . . . . . . . . . . . . . . . 32Cur bs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3- R Proj ects . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Tr af f i c Vol ume . . . . . . . . . . . . . . . . . . . . . . . 34Desi gn Speed . . . . . . . . . . . . . . . . . . . . . . . . 34Pavement & Shoul der Wi dt hs . . . . . . . . . . . . . . . . . 34Gr ades, Cur vat ur e & Si ght Di st ance . . . . . . . . . . . . . 35Br i dges . . . . . . . . . . . . . . . . . . . . . . . . . . . 35Hi st or i c St r uct ur es . . . . . . . . . . . . . . . . . . . . . 35

St ruct ures, Si gni ng & Mai nt enance . . . . . . . . . . . . . . . 36St r uct ur es . . . . . . . . . . . . . . . . . . . . . . . . . 36Si gni ng & Mar ki ng . . . . . . . . . . . . . . . . . . . . . . 36Mai nt enance . . . . . . . . . . . . . . . . . . . . . . . . . 36

GLOSSARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

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Li st of Tabl es

Tabl e Page

1 - Typi cal Desi gn Speeds f or Par k Roads . . . . . . . . . . . . 152 - Desi gn Vehi cl e Di mensi ons . . . . . . . . . . . . . . . . . 163 - Maxi mum Gr ades . . . . . . . . . . . . . . . . . . . . . . . 184 - K- Val ues f or Ver t i cal Curv es ,

St oppi ng & Passi ng Si ght Di st ance . . . . . . . . . . . 20

5 - Mi ni mum Radi us & Maxi mum Degr ee of Cur ve . . . . . . . . . . 226 - St oppi ng Si ght Di st ance . . . . . . . . . . . . . . . . . . 247 - St oppi ng Si ght Di s t ance, One- Lane Roads . . . . . . . . . . 258 - Mi ni mum Passi ng Si ght Di st ance . . . . . . . . . . . . . . . 269 - Si ght Di st ance at I nt er sect i ons . . . . . . . . . . . . . . 27

10 - Mi ni mum Roadway Cr oss- Sect i on Requi r ement s . . . . . . . . . 29

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Li st of Fi gures

Tabl e Page

1 - Typi cal Par k Road Syst em- - Funct i onal Cl assi f i cat i ons . . . . 52 - Typi cal Desi gn Vehi cl e- - Tur ni ng Pat h . . . . . . . . . . . . 173 - Typi cal Par k Road Cr oss- Sect i on . . . . . . . . . . . . . . 30

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THE PURPOSE OF PARK ROADS

Among al l publ i c r esour ces, t hose of t he Nat i onal Par k Syst em ar edi s t i ngui shed by thei r uni que nat ur al , hi s t or i cal , cul t ur al andr ecr eat i onal qual i t i esval ues dedi cat ed and set asi de by l aw t o bepr eser ved f or t he benef i t and enj oyment of peopl e i n such a manner aswi l l l eave t hem uni mpai r ed f or f ut ur e gener at i ons.

I deal l y, per haps no r oad woul d be per mi t t ed t o vi ol at e or despoi l t hesanct i t y of par k r esour ces. Pr agmat i cal l y, t he pr ot ect i on, use andenj oyment of t hese val ues i n a wor l d of moder n t echnol ogy hasnecessi t at ed t he encr oachment of a syst em of publ i c park r oads.

Today s vi si t or s ar e no l onger r equi r ed, as ear l y mot or i st t o Yel l owst one once wer e, t o chai n t hei r car s t o l ogs and t ur n over t hekeys t o t he super i nt endent . I n most par ks t oday, t he basi c means of pr ovi di ng f or vi si t or access i s t he par k r oad syst em. I t i s bot h ameans and an end. I t enabl es one vi si t or t o r each hi s goal ; f or

anot her , i t i s t he goal .

The mar ked i ncr ease of park vi si t or s i n t he l at t er hal f of t he 20 t h

cent ur y r epr esent s bot h a pr of ound t hr eat t o park val ues and anext r aordi nary opport uni t y f or t hose val ues t o become mor e t angi bl ysi gni f i cant i n each i ndi vi dual s recogni t i on of our nat ur al andcul t ur al her i t age.

The f undament al pur pose of nat i onal parks- br i ngi ng humanki nd and t heenvi r onment i nt o cl oser har mony- di ct at es t hat t he qual i t y of t he par kexper i ence must be our pr i mar y concer n. Ful l enj oyment of a nat i onal

par k vi si t depends on i t s bei ng a saf e and l ei sur el y exper i ence. Thedi st i nct i ve char act er of par k r oads pl ays a basi c rol e i n set t i ng t hi sessent i al unhur r i ed pace. Consequent l y, par k r oads ar e desi gned wi t hext r eme car e and sensi t i vi t y wi t h r espect t o t he t er r ai n andenvi r onment t hr ough whi ch t hey pass- t hey ar e l ai d l i ght l y ont o t hel and.

Each segment of ever y par k r oad shoul d r el at e t o t he r esour ce i tt r aver ses i n a meani ngf ul way and shoul d const i t ut e an enj oyabl e andi nf or mat i ve exper i ence i n i t sel f whi l e pr ovi di ng t he vi si t or t heut most i n vi sual qual i t y. Long t angent s t hat encour age hi gh speeds-and onl y f l eet i ng vi ews of ki net i c scener y- shoul d be avoi ded. Thehor i zont al and ver t i cal al i gnment and cr oss- sect i on shoul d r espect t het er r ai n, bl endi ng i nt o t he envi r ons. A par k r oad shoul d bef undament al l y desi gned t o mai nt ai n an over al l cont i nui ng sense of i nt i macy wi t h t he count r ysi de or ar ea t hr ough whi ch i t passes.

The pur pose of park r oads r emai ns i n shar p cont r ast t o t hat of t heFederal and St at e hi ghway syst ems. Par k r oads ar e not i nt ended t opr ovi de f ast and conveni ent t r anspor t at i on; t hey ar e i nt ended t o


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enhance vi si t or exper i ence whi l e pr ovi di ng saf e and ef f i ci entaccommodat i on of par k vi si t or s and t o ser ve essent i al managementaccess needs. They ar e not , t her ef ore, i nt ended nor desi gned ascont i nuat i ons of t he St at e and Feder al - ai d net wor k. Nor shoul d t heybe desi gned or desi gnat ed t o ser ve as connect i ng l i nks t o t hosesyst ems. And wi t hi n par ks, no r oad or ot her ci r cul at i on syst em shoul dbe pl anned or desi gned mer el y as a devi ce t o l i nk poi nt s of i nt er est .

As st at ed on a br ochur e t hat was once gi ven t o vi si t or s when t heyent ered Nat i onal Par ks:

Park roads are f or l ei surel y dr i vi ng onl y. I f you are i n ahur ry, you mi ght do wel l t o take another rout e now, and comeback when you have more t i me.

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FUNCTI ONAL CLASSI FI CATI ONS OF PARK ROADS

PARK ROAD SYSTEM

A par k r oad syst em i ncl udes t hose roads wi t hi n or gi vi ng access t o apar k or ot her uni t of t he Nat i onal Par k Syst em whi ch ar e admi ni st er edby t he Nat i onal Par k Ser vi ce, or by t he Ser vi ce i n cooper at i on wi t h

ot her agenci es ( 16 U. S. C. 8- 8f ) .

The Nat i onal Par k Syst em encompasses many t ypes of envi r onment s- -mount ai ns, f or est s, coast al zones, deser t s, and ur ban ar eas. Wi t hi neach par k, t her e of t en exi st s a var i et y of t er r ai ns whi ch of f erpot ent i al vi si t or exper i ences. Consequent l y, par k r oad syst ems mustbe appr opr i at el y desi gned t o serve a wi de r ange of f unct i ons i n accor dwi t h t he br oad st at ement of pur pose i n t he f oregoi ng chapt er.

For pur poses of f unct i onal cl assi f i cat i on, t he r out es whi ch make up apar k r oad syst em are grouped based on use i nt o t hr ee cat egori es:Publ i c Use Park Roads, Admi ni st r at i ve Par k Roads, and Ur ban Par kways

and Ci t y St r eet s.

The ass i gnment of a f unct i onal cl ass i f i cat i on t o a park r oad i s notbased on t r af f i c vol umes or desi gn speed, but on t he i nt ended use orf unct i on of t hat par t i cul ar r oad or r out e.

Publ i c Use Par k Roads

Al l par k r oads t hat ar e i nt ended pr i nci pal l y f or t he use of vi si t or sf or access i nt o and wi t hi n a par k or ot her Nat i onal Par k Syst em ar eaar e i ncl uded. Thi s i ncl udes al l r oads t hat pr ovi de vehi cul ar passagef or vi si t or s, or access t o such r epr esent at i ve par k ar eas as poi nt s of sceni c or hi st or i c i nt er est , campgr ounds, pi cni c ar eas, l odge ar eas,et c. Count y, St at e, and U. S. numbered hi ghways mai nt ai ned by t heSer vi ce ar e i ncl uded i n t hi s cat egor y f or pur poses of f unct i onalcl as si f i cat i on.

Publ i c Use Par k Roads are subdi vi ded i nt o t he f ol l owi ng f our cl asses:

Cl ass I : Pr i nci pal Park Road/ Rural Parkway. Roads whi ch const i t ut et he mai n access r out e, ci r cul at or y t our , or t hor oughf ar e f or par kvi si t or s .

Cl as s I I : Connect or Park Road. Roads whi ch pr ovi de access wi t hi n apar k t o ar eas of sceni c , sci ent i f i c , r ecreat i onal or cul t ur ali nt er est , such as over l ooks, campgr ounds, et c.

Cl ass I I I : Speci al Purpose Park Road. Roads whi ch pr ovi deci r cul at i on wi t hi n publ i c use ar eas, such as campgr ounds, pi cni car eas , vi s i t or cent er compl exes , concess i onai r e f aci l i t i es , et c .

These r oads gener al l y ser ve l ow- speed t r af f i c and ar e of t en desi gnedf or one- way ci r cul at i on.


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Cl ass I V: Pri mi t i ve Park Road

Roads whi ch pr ovi de ci r cul at i on t hr ough remot e ar eas and/ or access t opr i mi t i ve campgr ounds and undevel oped ar eas. These r oads f r equent l yhave no mi ni mum desi gn st andar ds and t hei r use may be l i mi t ed t ospeci al l y equi pped vehi cl es.

Admi ni st r at i ve Par k Roads

The Admi ni st r at i ve Par k Road cat egor y consi st s of al l publ i c and non-publ i c r oads i nt ended t o be used pr i nci pal l y f or admi ni st r at i vepur poses. I t i ncl udes r oads ser vi ci ng empl oyee r esi dent i al ar eas,mai nt enance ar eas and ot her admi ni st r at i ve devel opment s, as wel l asr es t r i c ted pat r ol r oads , t r uck t r ai l s , and s i mi l ar ser vi ce r oads .

Admi ni st r at i ve Par k Roads ar e subdi vi ded i nt o t wo cl asses:

Cl ass V: Admi ni st rati ve Access Road. Al l publ i c r oads i nt ended f or

access t o admi ni st r at i ve devel opment s or st r uct ur es such as parkof f i ces, empl oyee quar t er s, or ut i l i t y ar eas.

Cl ass VI : Rest r i ct ed Road. Al l r oads nor mal l y cl osed t o t he publ i c,i ncl udi ng pat r ol r oads, t r uck t r ai l s , and ot her si mi l ar r oads.

Fi gure 1 i l l us t r at es t he appl i cat i on of t hese f unct i onalcl assi f i cat i ons t o a hypot het i cal par k road syst em.

Ur ban Par kways and Ci t y St r eet s

Ur ban par kways and ci t y st r eet s ar e gener al l y dual - use f aci l i t i es i nt hat t hey serve bot h par k and non- par k rel at ed pur poses. I n addi t i ont o pr ovi di ng access t o par k ar eas, t hey al so ser ve as ext ensi ons of t he l ocal t r anspor t at i on net wor k car r yi ng hi gh vol umes of non- par kr el at ed t r af f i c.

Cl ass VI I : Urban Parkway. These f aci l i t i es ser ve hi gh vol umes of par k and non- par k r el at ed t r af f i c and ar e r est r i ct ed, l i mi t ed- accessf aci l i t i es i n an ur ban ar ea. Thi s cat egor y of r oads pr i mar i l yencompasses t he maj or par kways whi ch ser ve as gat eways t o our nat i on' scapi t al . Ot her par k r oads or por t i ons t her eof , however , may bei ncl uded i n t hi s cat egor y.

Cl as s VI I I : Ci ty St reet . Ci t y st r eet s ar e usual l y ext ensi ons of t headj oi ni ng st r eet syst em t hat ar e owned and mai nt ai ned by t he Nat i onalPar k Ser vi ce. The const r uct i on and/ or r econst r uct i on shoul d conf or mwi t h accept ed engi neer i ng pr act i ce and l ocal condi t i ons.


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* I n t hi s document , t he t erms " par k r oad" , " par k" and " Nat i onalPar k" ar e used gener i cal l y i n r ef er ence t o al l uni t s of t he Nat i onalPar k Syst em.

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FUNDAMENTAL CONSI DERATI ONS I N PARK ROAD DESI GN

Nat i onal par ks ar e uni que. I n t hat par k r oads ser ve a di st i nct l ydi f f er ent pur pose f r om most ot her r oads and hi ghways, Nat i onal Par kSyst em r oad st andards must al so be uni que.

Par k r oads* ar e const r uct ed onl y wher e necessary, and onl y asnecessar y, t o pr ovi de access f or t he pr ot ect i on, use and enj oyment of t he nat ur al , hi st or i cal , cul t ur al and r ecreat i onal r esour ces whi chconst i t ut e our Nat i onal Par k Syst em. Nat i onal par k r oadways, wheret hey exi st , ar e pl anned f or l ei sur el y si ght seei ng and ar e l ocat ed wi t hsensi t i ve concer n f or t he envi r onment and desi gned wi t h ext r eme car e.

They ar e of t en nar r ow, wi ndi ng, and hi l l y- - but t herei n may l i e t hei rappeal .

I n some cases, par k r oads pr ovi de such uni que exper i ences t hat t heyhave t hemsel ves become i nt er nat i onal l y r ecogni zed cul t ur al r esour ces- -

Skyl i ne Dr i ve i n Shenandoah Nat i onal Par k, Trai l Ri dge Road i n RockyMount ai n Nat i onal Par k, Goi ng- t o- t he- Sun Road i n Gl aci er Nat i onalPar k.

Thus, park r oads ar e of t en an end i n t hemsel ves, r at her t han j ust ameans t o an end, i n cont r ast t o mor e convent i onal hi ghway syst ems.For some, such as t he handi capped, r oads may pr ovi de t he onl y means of par k use, t her eby rei nf or ci ng t he case f or t hei r bei ng i nt i mat el ybl ended wi t h t he r esour ce. Where t er r ai n and saf et y condi t i ons per mi tand where such uses ar e advocat ed by t he gener al management pl an,oppor t uni t i es shoul d be pr ovi ded f or r andom st oppi ng t o enabl e par k

vi si t or s t o more compl et el y exper i ence t he park r esour ces.

Ur ban Par kways i n t he Washi ngt on, DC ar ea pr ovi de a broader ser vi cet han ot her par k r oads. They serve as at t r act i ve, l andscaped gat ewayst o our nat i on' s capi t al , and at t he same t i me, share many of t he hi gh-speed, hi gh- vol ume t r af f i c char act er i st i cs of expr essways of t he st at eand Feder al hi ghway net work. Due t o t he nat ur e of t r af f i c use on anUr ban Par kway, a hi gher st andar d f or desi gn i s necessar y t han i sr equi r ed f or most ot her par k r oads. The basi c cr i t er i a f or ur banpar kways must be consi st ent wi t h t he i nt ent of t he Legi sl at i on whi chaut hor i zed t hem. Pl anni ng, desi gn, operat i on and mai nt enance of ur banpar kways must consi der t r af f i c saf et y and pr ot ect and enhance t hel andscape, aest het i c, envi r onment al and cul t ur al char act er i st i cs andval ues whi ch si gni f i cant l y di st i ngui sh ur ban par kways f r omexpr essways. Ur ban par kways must be consi der ed as a whol e sys t em andal l desi gn el ement s such as l andscapi ng, si gns, l i ght i ng, guar dr ai l s,


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shoul der desi gn, cur bi ng, r amps, et c. , must be consi dered as el ement sof t he syst em. Thr ough car ef ul pl anni ng and desi gn, t hese par kwayscan ef f ect i vel y bl end hi gh- vol ume- t r af f i c saf et y wi t h t he aest het i cand ot her val ues of par k r oads.

The l ocat i on and desi gn of park r oads must cont i nue t o be i n accor dwi t h t he phi l osophy t hat how a per son vi ews a park i s as si gni f i cantas what he sees, t hereby ensuri ng t hat nat i onal parks r emai n pl aceswher e peopl e go f or a uni que and r ewar di ng exper i ence.

I n l i ne wi t h t hi s phi l osophy and Ser vi ce pol i ci es, pr ovi si on of r oadsi n a par k must be consi st ent wi t h appr oved management pl ans and bel i mi t ed t o t hose necessar y t o car r y out management obj ect i ves f or t hepar t i cul ar ar ea. Based on t he Ser vi ce' s pol i cy of mi ni mi zi ng r esour cei mpact s, and wher e vi si bl y compat i bl e, par k r oads ar e combi ned wi t hot her ser vi ces ( pi pe l i nes, power l i nes, et c. ) i nt o common cor r i dor s.

Thei r pr ovi si on, l ocat i on, desi gn, and const r uct i on and t heconst r uct i on mat er i al s used must be consi st ent wi t h t he perpet uat i on

and pr ot ect i on of t he r esour ces, aest het i c val ues of t he ar ea, andmai nt ai nabi l i t y of t he r oadway and r oadsi de. Whi l e park roads ar edesi gned di f f er ent l y f r om ot her r oads, t hey ar e desi gned, const r uct ed,and mai nt ai ned wi t hi n t he nor ms of sound geomet r i c s t andards f orsaf et y and st r uct ur al suf f i ci ency.

I n most par ks, a r oad syst em i s al r eady i n pl ace, havi ng beenconst r uct ed i n accor dance wi t h t he Nat i onal Par k Ser vi ce pol i ci es. I nupdat i ng pl ans f or t hese par ks, t he Ser vi ce wi l l eval uat e t he exi st i ngr oad syst em and det ermi ne whet her i t needs t o be cur t ai l ed, expanded,or s uppl ement ed by ot her c i r cul at ory modes. Where r oads ar e

chr oni cal l y bei ng used t o capaci t y, t he use of al t er nat et r anspor t at i on syst ems, l i mi t at i ons on use and ot her t r af f i cmanagement t echni ques shoul d be consi der ed as an al t er nat i ve t o r oadi mpr ovement s.

When t he Ser vi ce i s f aced wi t h a choi ce bet ween cr eat i ng a severe r oadscar t o br i ng vi s i t or s to a des t i nat i on poi nt , or r equi r i ng vi s i t or st o wal k a consi der abl e di st ance or t o ut i l i ze an al t er nat et r anspor t at i on syst em- - t he deci si on shoul d be agai nst t he scar . Thosewho vi si t nat i onal par ks do so f or a uni que experi ence, and shoul d bewi l l i ng t o accept necessar y r est r i ct i ons.

Par k r oads cannot accommodat e al l t ypes of vehi cl es, nor can t heyaccommodat e al l l evel s of speed, wi t hout vi ol at i ng t hese pr i nci pl es.Whi l e t he t r avel i ndust r y cont i nues t o devel op new ki nds of vehi cl es,t he Ser vi ce i s not obl i gat ed t o const r uct r oads or t o manage t r af f i cso t hat al l f orms of modern t r anspor t at i on t echnol ogy can beaccommodat ed wi t hi n t he par k.


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Recent t r anspor t at i on t r ends have si gni f i cant l y af f ect ed t he use of NPS r oads. There have been subst ant i al i ncr eases i n t he number s of r ecreat i onal vehi cl es ( RV' s) , bi cycl es, t our buses and smal l er l esspower f ul aut omobi l es usi ng park r oads s i nce 1968, when t he pr evi ousr oad desi gn st andar ds wer e adopt ed.

The gr owt h i n popul ar i t y of RV' s ( such as mot or - homes, pi ckup campers,and passenger car s wi t h t r avel t r ai l er s, whi ch ar e char act er i zed bygr eat er di mensi ons, sl ower oper at i on, and, f r equent l y, i nexper i encedoper at or s) i s a r el at i vel y r ecent phenomenon. The r ecr eat i on vehi cl er epr esent s a si gni f i cant el ement i n t he t r af f i c ser vi ce r equi r ement son par k r oads. Desi gn of par k r oads shoul d r ef l ect , t o t he ext entpossi bl e wher e such vehi cl es ar e per mi t t ed, t he f act t hat RV' s havedi f f er ent oper at i onal and saf et y char act er i st i cs t han aut omobi l es.

Bi cycl es ar e al so r api dl y becomi ng a si gni f i cant mode of pers onalt r anspor t at i on, par t i cul ar l y f or r ecreat i onal pur poses. Sceni cbi cycl e r i di ng and t our i ng have r ecent l y achi eved an unpr ecedent ed

popul ar i t y. Bi cycl e r i di ng on par k r oads shar ed wi t h aut omobi l es andot her vehi cul ar t r af f i c can be hazar dous and f r i ght eni ng f or bot hcycl i st s and mot or i st s. The nar r ow pavement sect i ons on many par kr oads cr eat e si gni f i cant hazar ds wher e bi cycl es, of t en l aden wi t hpi cni cki ng or campi ng gear , ar e mi xed wi t h ot her t r af f i c.

An i ncr ease i n t he number of t our buses on park r oads has been l argel ycaused by t wo r ecent t r avel t r ends: gr owt h i n t he domest i c mar ket of ol der per sons t r avel l i ng vi a t our buses t o Nat i onal Par ks and asubst ant i al i ncrease i n f or ei gn vi si t or s wi t h a cul t ur al pr ef er encef or or gani zed bus t our s. The gr owt h i n absol ut e numbers of l arge t our

buses on par k r oads has seri ous hi ghway saf et y i mpl i cat i ons, r esul t i ngf r om l ar ger number s of wi de vehi cl es oper at i ng on r el at i vel y nar r owr oads. The r esul t ant i ncr ease i n t he number of r epeat ed heavy- axl el oadi ngs i s al so det r i ment al t o t he ser vi ce l i f e of r oad pavement st hat wer e not desi gned f or t hat t ype of vehi cl e. Thi s has r esul t ed i ngr eat l y i ncr eased park r oad mai nt enance cost s.

When exi st i ng par k r oads ar e anal yzed, a det ermi nat i on of t he si ze andt ypes of vehi cl es t hat can be saf el y accommodat ed wi l l be made. I tmay be desi r abl e f or vehi cl es exceedi ng t hese l i mi t s t o be excl uded,r at her t han r econst r uct i ng t he r oads t o hi gher st andar ds. Appr opr i at eal t er nat i ves i ncl ude: pr ovi di ng par ki ng ar eas f or l ar ge vehi cl es atpar k ent r ances ; r es t r i c t i ng vehi cul ar t r af f i c i n cer t ai n por t i ons of apark; conver t i ng t wo- way r oads i nt o one- way syst ems; r educi ng speedl i mi t s t o pr ot ect bot h vi s i t or s and wi l dl i f e; and f ur ni shi ng al t er nat et r anspor t at i on syst ems.


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When new r oads ar e t o be const r uct ed, t hey shoul d be pl anned t opr eser ve t he i nt egr i t y of t he sur r oundi ngs, r espect ecol ogi calpr ocesses, pr ot ect par k r esour ces, pr ovi de t he hi ghest vi sual qual i t y,and meet moder n engi neer i ng and saf et y st andar ds commensur at e wi t h t hei nt ended use t o ensur e a f ul l y r ewar di ng and saf e vi si t or exper i ence.

These ar e t he pr i nci pl es whi ch di ct at e t he means of vi si t or access andt he devel opment of r oad desi gn st andards f or t he Nat i onal Par k Syst em.Saf eguar di ng t hese pr i nci pl es and appl yi ng t he st andar ds t hat f ol l owi s, t her ef or e, a mul t i - di sci pl i nar y under t aki ng- - a pr ocess combi ni ngt he pol i ci es and deci si ons of management wi t h t he t al ent s of engi neer s, desi gner s, pl anner s, ar chi t ect s, and l andscape ar chi t ect s,and i ncor por at i ng t he cont r i but i ons and exper t i se of pr ot ect i ve andi nt er pr et i ve pr of essi onal s, and cul t ur al and nat ur al r esour ces peci al i s t s .

* * *


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PARK ROAD DESI GN STANDARDS

Road desi gn i n t he Nat i onal Par k Syst em i s based on t he need t opr ovi de r easonabl e, l ei sur el y and saf e vi si t or access t o nat ur al ,sceni c, hi st or i c and r ecreat i onal f eat ur es and on f aci l i t at i ng t headmi ni st r at i on and pr ot ect i on of par k r esour ces.

Devel opment of t he exi st i ng syst em of r oads i n t he Nat i onal Par kSyst em uni t s t ook pl ace over a r el at i vel y l ong per i od of t i me.Roadway desi gns t hat wer e appr opr i at e f or t he t ypes and magni t ude of vehi cul ar t r af f i c when much of t he park r oad syst em was const r uct edmay no l onger be adequat e.

The r oad st andar ds devel oped herei n pr ovi de cr i t er i a based on t hosedesi gn el ement s consi der ed necessar y t o accommodat e t he var i ous,pot ent i al l evel s of vehi cul ar and pedest r i an use t hat Nat i onal Par kServi ce management may deci de t o permi t . The absol ut e cont r ol l i ng

f act or i n appl i cat i on of t hese st andar ds i s t he l evel of act ual , orper mi t t ed and cont r ol l ed use. The basi c al t er nat i ve avai l abl e, wher eappl i cat i on of a par t i cul ar st andar d i s deemed i ncompat i bl e wi t hr esour ce pr ot ect i on consi der at i ons, i s l i mi t at i on of l evel s of use,t ypes of use, or bot h.

I n l i ght of t he f oregoi ng, t hese st andards have been devel oped t opr ovi de def i ni t i ve gui del i nes f or t hose i nvol ved i n maki ng deci si onsaf f ect i ng t r af f i c ser vi ce and ci r cul at i on of par k vi s i t or s . They ar ei nt ended t o be appl i ed uni f orml y t o bot h new const r uct i on andr econst r uct i on of par k r oads on a Ser vi ce- wi de basi s t o t he ext ent

pr act i cabl e, based on pr oj ect i ons of act ual , or pl anned and cont r ol l eduse.

On r ehabi l i t at i on, r est or at i on and r esur f aci ng ( 3- R) pr oj ect s, t hest andar ds appl i cabl e t o new const r uct i on and reconst r uct i on wi l l i nsome i nst ances not be at t ai nabl e. Each 3- R pr oj ect must be consi deredon a case- by- case basi s t o det er mi ne t he f easi bi l i t y and l ong t er mcumul at i ve ef f ect s of any i mpr ovement s. ( See pp. 34 f f . )

Wher e r esour ce pr eser vat i on i ssues r el at i ng t o a const r uct i on,r econst r uct i on, or 3- R pr oj ect s pr ecl ude appl i cat i on of an appr opr i at edesi gn st andar d based on exi st i ng t r af f i c uses, t hen an al t er nat i ve i sr est r i ct i on of use t o a l evel consi st ent wi t h t he r oadway geomet r i eswhi ch can be devel oped wi t hout adver sel y af f ect i ng pr eser vat i on of t her esour ce. Thi s may be par t i cul ar l y desi r abl e i n unusual l y sensi t i venat ur al ar eas or i n conj unct i on wi t h hi st or i c si t es wher e t hei nt egr i t y of t he or i gi nal or r est or ed hi st or i c f abr i c may be

j eopar di zed.


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Of t en ci t ed as t he most i mpor t ant pr i nci pl e r el at i ng t o saf et y i n r oaddesi gn i s consi st ency. At t empt i ng t o conf or m al l desi gn el ement s andf eat ur es t o t he dr i ver ' s expect at i ons and avoi di ng abr upt changes i nt he appl i cat i on of st andar ds gr eat l y cont r i but es t o t he pr ovi si on of asmoot h- f l owi ng, acci dent - f r ee f aci l i t y.

DESI GN CONTROLS AND CRI TERI A

I n r oad desi gn, var i ous cont r ol s and cr i t er i a ar e empl oyed t o ensur et hat t he f aci l i t y wi l l saf el y accommodat e t he expect ed t r af f i cr equi r ement s and t o encour age consi st ency and uni f ormi t y of oper at i on.Pr i mar y consi derat i ons i n t he desi gn of park r oads ar e t he t ypes of t er r ai n t r aver sed, envi r onment al const r ai nt s, and t he desi r ed vi si t orexperi ence. These consi derat i ons ar e addr essed t hr ough t he sel ect i onand appl i cat i on of appr opr i at e desi gn cont r ol s. The maj or r oad desi gncont r ol s f or park r oads ar e desi gn vol ume, desi gn speed, and desi gnvehi cl e.

Desi gn Vol ume

A desi gn vol ume shoul d be est abl i shed t o r epr esent t he ant i ci pat ed, orpl anned and cont r ol l ed , t r af f i c use of t he r oadway dur i ng t he par k' snor mal vi si t or season. The desi gn vol ume descr i bes t he t r af f i c l oadt hat t he r oad must be abl e t o accommodat e at an appropr i at e l evel of ser vi ce and det er mi nes t o a l ar ge degr ee t he t ype of f aci l i t y andpavement wi dt hs r equi r ed, as wel l as ot her geomet r i c f eat ur es.

The cur r ent aver age dai l y t r af f i c ( ADT) may be used where pr esent

t r af f i c vol umes ar e bel ow 4, 000 vehi cl es per day and ar e not expect edt o gr ow si gni f i cant l y over t i me. For par k r oads t hat have a cur r entADT above 4, 000 vehi cl es per day and/ or t hat ar e exper i enci ng r api dgr owt h of t r af f i c, t he sel ect ed desi gn t r af f i c vol ume shoul d be basedon pl anned use pr oj ect ed t o some f ut ur e year - - usual l y up t o 20 year sbeyond t he year of const r uct i on. I t may not be pr act i cal , however ,( par t i cul ar l y f or ur ban parkways) t o desi gn t o accommodat e pr oj ect edt r af f i c.

On maj or r econst r uct i on pr oj ect s where r esour ce pr ot ect i on i ssueswhi ch conf l i ct wi t h t he r econst r uct i on ar e i dent i f i ed, a speci al st udywi l l be r equi r ed t o t horoughl y def i ne and eval uat e managemental t er nat i ves. Based on t he r esul t s of t hat anal ysi s of al t er nat i ves,a deci si on can be made as t o t he appropr i at e desi gn vol ume.

Desi gn Speed

Desi gn speed i s t he pr i mar y cont r ol t hat cor r el at es wi t h t he physi calf eat ur es of desi gn t o achi eve a r oadway t hat wi l l saf el y accommodat et r af f i c f or t he pl anned use. The desi gn speed af f ect s such r oadway


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f eat ur es as cur vat ur e, super el evat i on, si ght di st ance, and gr adi ent .Sel ect i on of t hi s speed i s pr i mar i l y i nf l uenced by t he pur pose of t hepar t i cul ar par k r oad, t he desi r ed t r af f i c vol umes, and t he char act erof t er r ai n and envi r onment al consi der at i ons.

Tabl e 1 shows t he r el at i onshi p of t ypi cal desi gn speeds t o t r af f i cvol umes f or t he di f f er ent cl asses of par k roads based on f l at ,r ol l i ng, and mount ai nous t er r ai n condi t i ons and was speci f i cal l ydevel oped t o pr ovi de a range of desi gn speeds appr opr i at e t o t he parkenvi r onment .

By r egul at i on, t he maxi mum post ed speed l i mi t f or any park r oad cannotexceed 45 mph, unl ess a Super i nt endent exerci ses hi s aut hor i t y t oest abl i sh a hi gher speed l i mi t wher e t hi s maxi mum l i mi t i s det er mi nedt o be l ess t han i s r easonabl e or saf e ( 36 CFR 4. 17) . Par k roads mayhave a desi gn speed up t o 10 mph hi gher t han t he post ed speed t o al l owa mar gi n f or saf et y.

Once a desi gn speed i s sel ect ed, al l geomet r i c f eat ur es shoul d ber el at ed t o i t . Changes i n t er r ai n and ot her physi cal cont r ol s, orenvi r onment al f act or s such as roadsi de wi l dl i f e may di ct at e a changei n desi gn speed f or cer t ai n segment s. Any decr ease i n desi gn speedal ong a r oad shoul d not be i nt r oduced abr upt l y; t hi s decr ease shoul dbe ext ended over a suf f i ci ent di st ance t o al l ow t he dr i ver t o adj ustt o t he t r ansi t i on t o a sl ower s peed. Pavement and shoul der wi dt hs andcl ear ances t o wal l s and r ai l s ar e l ess di r ect l y rel at ed t o desi gnspeed; however , t hey can af f ect capaci t y, vehi cl e speeds and saf et y.Consequent l y, hi gher st andar ds f or t hose f eat ur es shoul d be used onr oads wi t h hi gher desi gn speeds.

Desi qn Vehi cl e

Anot her maj or cont r ol i n geomet r i c desi gn of park r oads i s t he desi gnvehi cl e( s) , whi ch i s based on t he t ypes of vehi cl es t hat may bepermi t t ed by park management t o use t he f aci l i t y. The physi caldi mensi ons and oper at i ng char act er i st i cs of t he desi gn vehi cl e ar eused t o devel op si ght di st ance, cr oss- sect i on, i nt er sect i on desi gn andot her geomet r i c desi gn cr i t er i a. Exi st i ng and ant i ci pat ed t ypes of vehi cl es t o be usi ng park r oads must be exami ned t o est abl i shr epr esent at i ve vehi cl es f or use i n t he pr ocess of desi gni ng t her oadway.

Tabl e 2 i s pr ovi ded f or i nf or mat i onal pur poses onl y and l i st sper t i nent di mensi ons f or t en vehi cl e t ypes. Mi ni mum t ur ni ng pat hs of t he desi gn vehi cl es ar e par t i cul ar l y i mpor t ant . The gover ni ng pat hsare t hose of t he out er f r ont over hang and t he i nner r ear wheel . Theout er f r ont wheel i s assumed t o f ol l ow a ci r cul ar ar c, whi ch i s t hemi ni mum t ur ni ng r adi us as det er mi ned by t he vehi cl e' s st eer i ngmechani sm. Fi gure 2 i l l ust r at es t hese r equi r ement s f or a t ypi caldesi gn vehi cl e.


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I nt er r el at i onshi p of Desi gn Cont r ol s

The r oad desi gn pr ocess i nvol ves i dent i f yi ng on a segment - by- segmentbasi s t he desi gn speed f or a pl anned desi gn vol ume and sel ect ed desi gnvehi cl e.

Desi gn speed f or par k r oads i s l argel y det er mi ned by t he char act er of t he ter r ai n, t he r esour ce t r aver sed, and t he pl anned vi si t orexper i ence as descr i bed i n t he par k' s General Management Pl an. I ncases where t hese consi derat i ons cont r ol desi gn speed, t he pl anneddesi gn vol ume and/ or desi gn vehi cl e may r equi r e appr opr i at eadj ust ment .

For desi gn pur poses, t opogr aphy i s gener al l y cl assi f i ed based on t hr eet ypes of t er r ai n condi t i ons:

S Level t er r ai n i s t hat condi t i on wher e hi ghway si ght di st ances, i nr el at i on t o bot h hor i zont al and ver t i cal r es t r i c t i ons , ar e gener al l y

l ong, or can be made so, wi t hout const r uct i on di f f i cul t y or undueadver se af f ect s.

S Rol l i ng t er r ai n i s t hat condi t i on wher e t he nat ur al sl opesconsi st ent l y r i se above and f al l bel ow t he r oad gr ade, and wher eoccasi onal st eep sl opes of f er some r est r i ct i on t o nor mal hor i zont aland ver t i cal r oadway al i gnment .

S Mount ai nous t er r ai n i s t hat condi t i on wher e l ongi t udi nal andt r ansver se changes i n gr ound el evat i on, wi t h r espect t o t he r oad,ar e abr upt , f r equent l y requi r i ng benchi ng and si dehi l l excavat i on t o

obt ai n accept abl e hor i zont al and ver t i cal al i gnment .


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T a b l e

1

T y p i c a

l D e s i g n

S p e e

d s ( m p h )

F U N C T I O N A L

C L A S S I F I C A T I O N

D E S I G N V O L U M E

V e h i c l e s

/ D a y

T E R R A I N

F L A T

D e s i g n

S p e e

d

R O L L I N G

D e s i g n

S p e e

d

M O U N T A I N

D e s i g n

S p e e

d

P r e

f e r r e d

M i n i m u m

P r e

f e r r e d

M i n i m u m

P r e f e r r e

d

M i n i m u m

I - P r i n c i p a

l P a r k

R o a d a n

d R u r a l

P a r k w a y

< 2 0 0

4 0

3 0

3 5

2 5

3 0

2 0

2 0 0 - 4 0 0

5 0

4 0

4 0

3 0

3 0

2 0

4 0 0 - 1 0 0 0

5 0

4 0

4 0

3 0

3 5

2 5

1 0 0 0

- 4 0 0 0

5 5

4 5

4 5

3 5

4 0

3 0

4 0 0 0

- 8 0 0 0

6 0

5 0

5 0

4 0

4 0

3 0

> 8 0 0 0

6 0

5 0

6 0

5 0

5 0

4 0

I I - C

o n n e c t o r ,

I I I - S p e c

i a l

P u r p o s e ,

V - A d m i n i s t r a

t i v e ,

o r

V I - R

e s t r i c t e d

< 4 0 0

3 0

1 5

3 0

1 5

3 0

1 5

4 0 0 - 1 0 0 0

3 5

2 5

3 5

2 5

3 0

1 5

1 0 0 0

- 4 0 0 0

4 0

2 5

4 0

2 5

3 5

2 5

> 4 0 0 0

4 0

2 5

4 0

2 5

4 0

2 5

V I I - U r b a n

P a r k w a y

< 4 0 0 0

5 5

4 5

4 5

4 0

4 5

4 0

4 0 0 0

- 8 0 0 0

6 0

5 0

5 0

4 0

4 5

4 0

> 8 0 0 0

6 5

5 5

6 0

5 0

5 0

4 0

N o t e :

P o s t e d s p e e

d s w i

l l n o r m a l

l y b e 5 - 1 0 m p h

l e s s

t h a n

d e s i g n s p e e

d a t d e s i g n s p e e

d s a b o v e 3

0 m p

h .

E n v i r o n m e n

t a l c o n c e r n s s h o u

l d b e c o n s

i d e r e d

w h e n s e

l e c t

i n g

d e s i g n s p e e

d .


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16

T a b l e

2

D e s i g n

V e h i c l e

D i m e n s

i o n s

( D i m e n s i o n s

i n F e e t

)

D e s i g n

V e h i c l e

T y p e

S y m b o l

W h e e

l b a s e

F r o n

t

O v e r

h a n g

R e a r

O v e r

h a n g

O v e r a l

l

L e n g

t h

O v e r a l

l

W i d t h

H e i g h t

M i n .

T u r n i n g

R a d

i u s

M i n .

I n s i

d e

R a d i u s

P a s s e n g e r

C a r

P

1 1

3

5

1 9

7

-

2 4

1 5 . 3

P a s s e n g e r

C a r w /

T r a v e l

T r a i

l e r

P T

3 4

3

1 0

4 9

8

-

2 4

5 . 5

P a s s e n g e r

C a r w /

B o a t

T r a i

l e r

P B

3 1

3

8

4 2

8

-

2 4

1 0 . 0

M o t o r

H o m e

M H

2 0

4

6

3 0

8

1 3 . 5

4 2

2 8 . 4

S i n g

l e U n i t T r u c

k

S U

2 0

4

6

3 0

8 . 5

1 3 . 5

4 2

2 8 . 4

S i n g

l e U n i t B u s

B u s

2 5

7

8

4 0

8 . 5

1 3 . 5

4 2

2 3 . 2

A r t i c u

l a t e d B u s

A - B u s

1 8 + 2

4 = 4 2

8 . 5

9 . 5

6 0

8 . 5

1 3 . 5

3 8

2 1 . 0

S e m i - T

r a i l e r

C o m b

i n a t

i o n ,

I n t e r m e d

i a t e

W B - 4

0

1 3 + 2

7 = 4 0

4

6

5 0

8 . 5

1 3 . 5

4 0

1 9 . 9

S e m i - T

r a i l e r

C o m b

i n a t

i o n ,

I n t e r m e d

i a t e

W B - 5

0

2 0 + 3

0 = 5 0

3

2

5 5

8 . 5

1 3 . 5

4 5

1 9 . 8

S e m i - T

r a i l e r

C o m b

i n a t

i o n ,

I n t e r m e d

i a t e

W B - 6

0

9 . 7 + 2 0 + 9 .

4 + 2

0 . 9 = 6 0

2

3

6 5

8 . 5

1 3 . 5

4 5

2 2 . 5

C o m p

i l e d

F r o m :

A P o l i c y o n

G e o m e t r i c

D e s i g n o f

H i g h w a y s a n

d S t r e e

t s .

A A S H T O

, 1 9 8 4


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18

DESI GN ELEMENTS

The f or egoi ng cont r ol s and cr i t er i a have a maj or i nf l uence on t hegeomet r i es of park roads and ot her el ement s of desi gn. The el ement swhi ch f ol l ow have been t ai l or ed t o meet t he speci al needs andl i mi t at i ons of Nat i onal Par k Syst em r oads. Whi l e al l t hese el ement sar e cl osel y i nt er r el at ed, each i nf l uenci ng t he ot her s, al l must bepr oper l y coor di nat ed i n t hei r appl i cat i on t o a par t i cul ar pr oj ect .

Key among t he park r oad desi gn el ement s ar e hor i zont al and ver t i calal i gnment , whi ch have a subt l e, yet ver y i mpor t ant i nt er r el at i onshi p.

The t opogr aphy of t he l and t r aver sed i nf l uences bot h, but i s mor eevi dent i n ver t i cal al i gnment . I t i s t he ski l l f ul mani pul at i on of t hese t wo el ement s i n a manner compat i bl e wi t h t he t er r ai n t r aver sedwhi ch r esul t s i n t he most di s t i nct i ve t r adi t i onal char acter i s t i c of par k r oads- - cur vi l i near al i gnment .

Ver t i cal Al i gnment

Ver t i cal al i gnment consi st s of ascendi ng and descendi ng gr adesconnect ed by par abol i c cur ves.

Gr ades - Maxi mum al l owabl e desi gn gr ades i n r el at i on t o desi gn speedand t ype of t opogr aphy ar e shown i n Tabl e 3.

Tabl e 3

Maxi mum Desi gn Gr ades i n Per cent

Type of Topography

Desi gn Speed ( mph)

15 20 25 30 35 40 45 50 55 60 65

Fl at 8 8 7 7 7 7 6 5 4 4 3

Rol l i ng 11 11 10 10 9 9 8 7 6 5 4

Mount ai n 17 16 15 14 13 12 10 9 7 6 6

Compi l ed From: A Pol i cy on Geomet r i c Desi gn of Hi ghways andSt r eet s. AASHTO, 1984


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19

Maxi mum desi gn gr ade shoul d be used very i nf r equent l y, and shoul d notbe consi der ed a val ue t o be appl i ed i n most cases. The gr ades showni n Tabl e 3 r el at e pr i mar i l y t o t he oper at i onal per f or mance of vehi cl es. Ot her concer ns i n t he sel ect i on of a maxi mum gr ade ar e t hecapabi l i t y of t he soi l f or er osi on r esi st ance, t he t ype of sur f ace andcr oss- sect i on of t he r oadway, t he dr ai nage t r eat ment , and t he l engt hof maxi mum gr ade.

Shor t gr ades, l ess t han 500 f eet i n l engt h, and one- way down- gr adesmay be 1% st eeper t han t hose shown i n Tabl e 3. I n ext r eme cases( e. g. , at some under passes and br i dge appr oaches) , st eeper gr ades f orr el at i vel y shor t l engt hs may be consi dered. For l ow- vol ume r oads,grades may be 2% st eeper .

Cr i t i cal l engt h of gr ade i s usual l y not a maj or concer n f or par kr oads. However , appr opr i at e consi der at i on shoul d be gi ven t o t hi sel ement of desi gn f or r oads const r uct ed at hi gher desi gn speeds orr oads wi t h l ar ge number s of t our buses or r ecr eat i onal vehi cl es.

Fl at and l evel gr ades ar e not obj ect i onabl e on uncurbed pavement whent he cr own i s adequat e t o dr ai n t he sur f ace l at er al l y. On cur bedpavement s, a mi ni mum gr ade of 0. 5% i s nor mal l y r equi r ed, but a gr adeof 0. 35% may be used where t here i s hi gh qual i t y pavement , accur at el ycr owned and suppor t ed by f i r m subgr ade.

Ver t i cal Cur ves - Ver t i cal cur ves ar e used t o ef f ect a gr adual changebet ween t angent gr ades. Ver t i cal cur ves shoul d be si mpl e i nappl i cat i on and r esul t i n a desi gn t hat i s saf e, comf or t abl e i noperat i on, pl easi ng i n appearance, and adequat e f or dr ai nage.

The maj or cont r ol f or saf e oper at i on on cr est ver t i cal cur ves i s t hepr ovi si on of ampl e si ght di st ances f or t he desi gn speed. Mi ni mumst oppi ng si ght di st ance shoul d be pr ovi ded i n al l cases. Addi t i onalst oppi ng si ght di st ance shoul d be pr ovi ded at deci si on poi nt s( i nt er sect i ons, over l ooks, et c. ) and, wher e f easi bl e, mor e l i ber aldi st ances shoul d be used.

The r at e of gr ade changes shoul d be kept wi t hi n t ol er abl e l i mi t s. Thi s consi derat i on i s most i mpor t ant i n sag ver t i cal cur ves, wheregr avi t at i onal and ver t i cal cent r i f ugal f or ces act i n t he samedi r ect i on. Appear ance shoul d al so be consi der ed- - a l ong cur ve i sgeneral l y more pl easi ng i n appear ance t han a shor t one, whi ch may gi vet he appearance of a sudden br eak i n t he pr of i l e due t o t he ef f ect of f or eshor t eni ng, par t i cul ar l y when combi ned wi t h hor i zont al cur vat ur e.Wher ever bot h hor i zont al and cr est ver t i cal cur ves ar e r equi r ed, t hecrest ver t i cal cur ves shoul d f al l wi t hi n t he hor i zont al cur ve.


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For si mpl i ci t y, a par abol i c cur ve i s used t o af f ect a gr adual changebet ween gr ades. Par abol i c cur ves ar e i dent i f i ed by t hei r l engt hs andt he al gebr ai c di f f er ence of t he gr ades t hey connect . The mi ni muml engt h of ver t i cal cur ve may be comput ed f r om t he f ol l owi ng f ormul a:

L = KA , wher e:

L = t he l engt h of t he ver t i cal cur ve i n f eet ;

K = t he di st ance i n f eet r equi r ed t o af f ect a one per cent changei n gr adi ent ; and

A = t he al gebr ai c di f f er ence i n gr ades i n per cent .

The sel ect i on of a K val ue f or cr est ver t i cal cur ves i s based on si ghtdi st ance r equi r ement s. For sag ver t i cal cur ves, K i s based onheadl i ght si ght di st ance, usi ng cr i t er i a based on a l i ght beamemanat i ng f r om a sour ce 2. 0 f eet above t he pavement on a 10 upwar d

di ver gence f r om t he l ongi t udi nal axi s of t he vehi cl e t o wher e t he beami nt er sect s t he r oadway sur f ace. The f or mul a comput es mi ni mum l engt hsof ver t i cal cur ve f or ei t her cr est or sag cur ves; however , K val uesar e di f f er ent f or each desi gn speed and condi t i on. Tabl e 4 gi ves t heK val ues t o be used.

Tabl e 4K Val ues f or Ver t i cal Cur ves

Stoppi ng Si ght Di st ance

Desi gnSpeed Passi ng Si ghtDi st ance Cr est Cur ves Sag Cur ves

mph f t . Mi ni mum Desi r abl e Mi ni mum Desi r abl e15 149 5 5 8 820 210 10 10 20 2025 300 20 20 30 3030 400 30 30 40 4035 550 40 50 50 5040 730 60 80 60 7045 890 80 120 70 9050 1050 110 160 90 11055 1230 150 220 100 13060 1430 190 310 120 16065 1720 230 400 130 180

Compi l ed From: A pol i cy on Geomet r i c Desi gn of Hi ghways andSt r eet s. AASHTO, 1984


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21

Gener al Consi der at i ons i n Ver t i cal Al i gnment - I n addi t i on t o gr adeand ver t i cal cont r ol s, appl i ed i n concer t wi t h t he cri t er i a of pr ovi di ng saf et y and r espect i ng t he t er r ai n, ot her consi der at i ons i ndesi gni ng ver t i cal al i gnment i ncl ude:

1. Smoot h gr adel i nes wi t h gr adual changes, consi st ent wi t h t he cl assof par k road and char act er of t er r ai n, ar e pr ef er abl e t o a l i ne

wi t h numer ous br eaks and shor t l engt hs of gr ade.2. "Rol l er coas ter" or " hi dden- di p" pr of i l es shoul d be avoi ded.

These t ypes of pr of i l es ar e aest het i cal l y unpl easant andhazar dous.

3. Undul at i ng gr adel i nes wi t h re l at i vel y l ong gr ades shoul d beeval uat ed t o det er mi ne t hei r ef f ect on t r af f i c oper at i on,par t i cul ar l y wher e t her e ar e si gni f i cant vol umes of r ecr eat i onalvehi cl es and t our buses.

4. A br oken- back gr adel i ne ( t wo ver t i cal cur ves i n t he samedi r ect i on separ at ed by shor t sect i ons of t angent gr ade) gener al l yshoul d be avoi ded, par t i cul ar l y i n sags wher e t he f ul l vi ew of bot h ver t i cal cur ves i s not pl easi ng.

5. On l ong gr ades, i t may be pr ef er abl e t o pl ace t he st eepest gr adesat t he bot t om and t o l i ght en t he gr ades near t he t op of t heascent , or t o br eak t he sust ai ned gr ade wi t h shor t i nt er val s of l i ght er grade, i nst ead of ut i l i zi ng a uni f or m sust ai ned gr ade.

Thi s i s par t i cul ar l y appl i cabl e t o l ow- desi gnspeed r oads.

6. Gr ades t hr ough at - gr ade i nt er sect i ons on r oads wi t h moder at e orst eep gr ades shoul d be 6% or l ess whenever possi bl e.

Hor i zont al Al i gnment

Hor i zont al al i gnment consi st s of t angent s and hor i zont al cur ves t hatar e ci r cul ar cur ves wi t h const ant r adi us. Tr ansi t i onal spi r al cur vesmay be used t o connect t he t angent s t o t he hori zont al cur ve. Cr i t eri af or det er mi ni ng mi ni mum r adi us ( or maxi mum degr ee of cur vat ur e) arebased on l aws of mechani cs, wi t h desi gn val ues dependi ng on pr act i call i mi t s f or super el evat i on and f r i ct i onal f act or s repr esent at i ve of pavement sur f aces.

Maxi mum super el evat i on r at es are cont r ol l ed by sever al f act or s t hatmay var y wi del y: ( 1) f r equency and amount of snow and i ce; ( 2) ext entof devel opment i n t he ar ea; and ( 3) f r equency of sl ow- movi ng vehi cl es.Maxi mum superel evat i on ( e) val ues r ange upwar d t o 0. 12 f or r oadways i nundevel oped ar eas where t here i s no snow and i ce. Consi der at i onshoul d be gi ven t o l i mi t i ng maxi mum superel evat i on on st eep gr ades.Anot her var i abl e t hat i nf l uences maxi mum cur vat ur e i s t he si def r i ct i on f act or ( f ) . The mi ni mum r adi i and maxi mum degr ee of cur vat ur ef or var i ous desi gn speeds i n r el at i on t o super el evat i on r at e ar e showni n Tabl e 5 .


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I n addi t i on t o t he cont r ol s on maxi mum cur vat ur e, t her e i s a need t opr ovi de mi ni mum st oppi ng si ght di st ance ar ound cur ves whi ch maycont r ol t he mi ni mum r adi us of cur ve when si ght di st ance cannotot herwi se be pr ovi ded by r emovi ng t he si ght obst r uct i on.

Super el evat i on Runof f and Tr ansi t i on Cur ves - Spi r al cur ves used as at r ansi t i on bet ween cur ves and t angent sect i ons pr ovi de a nat ur al ,easy- t o- f ol l ow dr i vi ng pat h, can enhance r oadway appear ance, andpr ovi de a desi r abl e ar r angement f or super el evat i on runof f .

Gener al Cont r ol s f or Hor i zont al Al i gnment - I n addi t i on t o t hespeci f i c desi gn el ement s f or hor i zont al al i gnment , t her e ar e t hef ol l owi ng ot her gener al cont r ol s:

1. Al i gnment shoul d be as di r ect i onal as possi bl e cons i s tent wi t ht opogr aphy and r esour ce pr ot ect i on consi der at i ons; l ong f l owi ngcur ves f i t t o t he t opogr aphy ar e pr ef er abl e t o l ong t angent swhi ch s l ash ar t i f i c i al l y across the l and.

2. Two l ane r oad al i gnment s shoul d pr ovi de as many saf e passi ngsect i ons as possi bl e. Tur n- out s may be pr ovi ded as anal t er nat i ve when passi ng sect i ons ar e not f easi bl e.

3. Maxi mum al l owabl e degr ee of cur vat ur e shoul d be avoi ded wheneverpossi bl e.

4. Consi st ent al i gnment shoul d be sought ; shar p cur ves at t he end of l ong t angent s or at t he end of l ong, f l at cur ves shoul d beavoi ded.

5. Shor t l engt hs of cur ves shoul d be avoi ded on f l at cur ves t o avoi dt he appear ance of a ki nk.

6. Compound ci r cul ar cur ves, shoul d gener al l y be avoi ded, but i f used di f f er ences i n r adi i shoul d not exceed a r at i o of 2 t o 1 att he l ower desi gn speeds, and shoul d not exceed a r at i o of l t o1 at desi gn speeds above 50 mph.

7. I n gener al , di r ect r ever se cur ves shoul d be avoi ded, and at angent l engt h shoul d be used bet ween t hem.

8. "Br oken- back cur ves" ( t wo cur ves i n t he same di r ect i on on ei t hersi de of a shor t t angent or l ar ge r adi us cur ve) shoul d be avoi ded.

9. The hor i zont al al i gnment shoul d be coor di nat ed car ef ul l y wi t h t hever t i cal al i gnment . The begi nni ng and endi ng of ver t i cal andhori zont al cur ves shoul d not occur at t he same st at i on.


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Si ght Di st ance

Si ght di st ance i s t he l engt h of r oadway on whi ch anot her vehi cl e orobst r uct i on i s cont i nuousl y vi si bl e t o t he dr i ver . Mi ni mum st oppi ngsi ght di st ance and passi ng si ght di st ance ar e di r ect l y r el at ed t o t hedesi gn speed of t he r oad. I nt er sect i on cor ner si ght di st ance i s adi r ect f unct i on of t he desi gn speed of t he t hr ough r oad onl y when t hemi nor r oad i s st op cont r ol l ed.

St oppi ng- Si ght Di st ance - St oppi ng si ght di st ance used f or r oad desi gni s t he sum of t wo di st ances: ( 1) t he di st ance a vehi cl e t r avel s af t ert he dr i ver si ght s an i mmobi l e vehi cl e or obj ect i n t he r oadway andbef or e br aki ng occur s; and ( 2) t he di st ance t r avel ed dur i ng br aki ng.Cr i t er i a f or measuri ng st oppi ng si ght di st ance assume an eye hei ght of 3. 5 f eet and an obj ect hei ght of 6 i nches.

The mi ni mum and desi r abl e st oppi ng si ght di st ances f or r oads atvar i ous desi gn speeds ar e shown i n Tabl e 6 . Mi ni mum di st ances assume

t hat t he vehi cl e i s t r avel i ng at l ess t han t he desi gn speed, whi l e t hedesi r abl e di st ances assume t hat t he vehi cl e i s t r avel i ng at t he desi gnspeed.

Tabl e 6St oppi ng Si ght Di st ance

( Wet Pavement s)

Stoppi ng Si ght Di st ance *Desi gn Speed

( mph)Mi ni mum

( f t )Desi rabl e

( f t )15 80 8020 125 12525 150 15030 200 20035 225 25040 275 32545 325 40050 400 47555 450 55060 525 65065 550 725

* Di st ances r ounded f or desi gn.

Compi l ed From: A Pol i cy on Geomet r i c Desi gn of Hi ghways and St r eet s.AASHTO, 1984


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On t wo- di r ect i onal , one- l ane r oads, enough si ght di st ance must beal l owed t o enabl e one of t wo vehi cl es appr oachi ng f r om opposi t edi r ect i ons t o r each a t ur nout or f or bot h t o st op bef or e col l i di ng.Cr i t er i a f or measur i ng st oppi ng si ght di st ance f or one- l ane roadsassume an eye hei ght of 3. 5 f eet and an opposi ng- vehi cl e hei ght of 4. 25 f eet . The st oppi ng si ght di st ance f or a t wo- way, one- l ane r oadmust be appr oxi mat el y t wi ce t he st oppi ng si ght di st ance f or a t wo- l aner oad. Suggest ed st oppi ng si ght di st ances and " K " val ues f or one- andt wo- di r ect i onal , one- l ane r oads ar e gi ven i n Tabl e 7 .

A " K " val ue i s a coef f i ci ent by whi ch t he al gebr ai c di f f er ence i ngr ade i s mul t i pl i ed t o det er mi ne t he l engt h i n f eet of t he ver t i calcur ve whi ch wi l l pr ovi de mi ni mum si ght di st ance. The l engt h i n f eetshoul d not be l ess t han t hr ee t i mes t he desi gn speed i n mph f or anyver t i cal cur ve.

Tabl e 7St oppi ng Si ght Di st ance

One- Lane Roads

Desi gn Speed ( mph) 15 20 25 30 35 40 45 50 55

One- Di rect i onalOne- Lane RoadsSt oppi ng Si ght - mi ni mumDi s tance ( f t ) - des i r abl e

80 125 150 200 225250

275325

325400

400475

450550

K Val ues f or :

Cr est Ver t i cal - mi ni mumCur ve - desi r abl e 5 10 20 30 4050 608 80120 110160 150220Sag Ver t i cal - mi ni mumCurve

8 20 30 40 5050

6070

7090

90110

100130

Two- Di rect i onalOne- Lane Roads

( These desi gn speedsar e not r ecommended for

two- di rect i onal , one-l ane roads. )

St oppi ng Si ghtDi st ance ( f t ) 175 250 400

K Val ues f or :Cr est Ver t i cal Cur veSag Ver t i cal Cur ve

1011

2020

5240

Compi l ed From: A Pol i cy on Geomet r i c Desi gn of Hi ghways andSt r eet s. AASHTO, 1984


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I t i s advi sabl e t o pr ovi de suf f i ci ent wi dt h f or a vehi cl e t o passanot her vehi cl e st opped at t he i nt er sect i on. The combi nat i on of t hewi dt h of t he mai n r oad and t he r adi us of t he t aper of t he i nt er sect i ngr oad shoul d pr ovi de adequat e wi dt h f or vehi cl es ent er i ng or l eavi ngt he mai n r oad. For i nt er sect i ons wher e si gni f i cant vol umes of t ur ni ngmaneuver s occur , consi der at i on shoul d be gi ven t o pr ovi di ng t ur ni ngl anes. Wher e t ur ni ng r oadways ar e used, adequat e l engt hs f ormerge/ di ver ge l anes shoul d be pr ovi ded.

Number of Lanes

The number of l anes shoul d be suf f i ci ent t o accommodat e t he desi gnt r af f i c vol ume. For l ow- vol ume par k r oads, capaci t y condi t i ons do notnor mal l y gover n desi gn, and t wo t r avel l anes ar e appr opr i at e.However , on ext r emel y l ow- vol ume access r oads t o r emot e ar eas, one-l ane, t wo- way r oads wi t h f r equent t ur nout s may be consi dered. Wherepass i ng oppor t uni t i es ar e s i gni f i cant l y l i mi t ed, auxi l i ar y pass i ngl anes or t ur nout s shoul d be consi dered. When t he desi gn vol ume

exceeds 8, 000, a f our - l ane di vi ded r oadway sect i on may be r equi r ed t oaccommodat e t r af f i c. For mul t i - l ane r oads, t he desi gn hour l y vol umecont r ol l i ng l ane capaci t y i s 1, 500 vehi cl es/ hour / l ane.

Cr oss- Sect i on

The r oadway cr oss - sect i on consi st s of t r avel ed ways, auxi l i ar y l anes,shoul ders , medi ans, and r oadsi des. Proper r oadway wi dt h i s sel ect edon t he basi s of numerous f act or s i ncl udi ng park r esour ceconsi der at i ons, exi st i ng and/ or pl anned vol umes and t ypes of t r af f i c,saf et y, t er r ai n, and desi gn speed. A t ypi cal cross- sect i on of par k

road i s i l l us t r at ed i n Fi gure 3 .

Tr avel ed Way - The t r avel ed way i s t hat por t i on of t he r oadwayavai l abl e f or movement of vehi cl es, excl usi ve of shoul der s andauxi l i ar y l anes. I t i s usual l y compr i sed of t wo or mor e t r af f i cl anes.

Shoul ders - The t er m shoul der descr i bes t hat por t i on of t he r oadway,cont i guous wi t h t he t r avel ed way, i nt ended f or t he accommodat i on of st opped vehi cl es, f or emer gency use, and f or l at er al suppor t of subbase, base, and sur f ace cour ses. The shoul der on park r oads wi t hl ow t r af f i c vol umes ser ves essent i al l y as st r uct ur al l at er al suppor tf or t he road surf aci ng and as an addi t i onal emergency wi dt h f or t henar r ower t r avel ed way. Wher e t here i s appr eci abl e t r af f i c vol ume,r oads wi t h nar r ow sur f aci ng and nar r ow shoul der s of t en gi ve poort r af f i c ser vi ce, may have hi gh acci dent exper i ence, and r equi r ef r equent and cost l y mai nt enance. The l ow t r af f i c vol umes andr el at i vel y l ow operat i ng speeds on most park r oads do not war r ant wi deshoul ders .


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I n addi t i on, wi de shoul der s may be envi r onment al l y and aest het i cal l yobj ect i onabl e, or may encour age undesi r abl e r andom st oppi ng orpar ki ng. However , as desi gn vol umes, desi gn speeds or vehi cl e si zesi ncr ease, addi t i onal shoul der wi dt h i s r equi r ed f or saf et y andst r uct ur al suppor t . Shoul der s may be di r t , gr avel , paved, t ur f ,st abi l i zed t ur f or a combi nat i on of sur f aces, dependi ng upon l andsur f ace t ype, bi cycl e use, cl i mat e, mai nt ai nabi l i t y and aest het i cobj ect i ve.

These f act s and concer ns ar e r ef l ect ed i n t he l ane and shoul der wi dt hsshown i n Tabl e 10 .

Tabl e 10Mi ni mum Roadway Cr oss- Sect i on Requi r ement s

AverageDai l y

Traff i c( ADT)

Number of

Lanes

Lane Wi dth

Feet a/

Shoul derWi dth

Feet / Si de

Lane Surf ace

Type(s)

8000 4 12 8 b/ Paved

a/ Wi deni ng of t r af f i c l anes shoul d be pr ovi ded on t he i nsi deof shar p curves. Wher e t our buses ar e al l owed or t hepr opor t i on of r ecr eat i onal vehi cl es exceeds 5% of t he desi gnvol ume, an addi t i onal f oot of l ane wi dt h shal l beconsi dered, not t o exceed 12 f eet .

b/ Woul d onl y appl y, as appr opr i at e, t o ur ban parkways.

Where guardr ai l i s used, t he gr aded wi dt h of shoul der shoul d bei ncr eased t o pr ovi de about 2 f eet out si de t he guar dr ai l post s t opr ovi de l at er al suppor t .

The t ot al r oadway wi dt h ( i ncl udi ng shoul ders) f or l ow- vol ume, one-l ane, one- way r oads s houl d not exceed 14 f eet because of t he t endencyof dr i ver s t o use a wi der f aci l i t y as a t wo- l ane r oad.


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Recr eat i on Ar eas

As a r ul e, Cl ass I r oads i n ar eas used pr i mar i l y f or r ecr eat i on ser vef unct i ons br oader t han ot her par k r oads. Accor di ngl y, where necessar yt o accommodat e recr eat i onal vehi cl es and boat t r ai l er use, t r avel ed-way wi dt hs f or t wo- way r oads i n r ecr eat i on ar eas shoul d be 24 f eet of pavement ( t wo 12' l anes) pl us shoul der s of 4 f eet . I n t hoser ecr eat i on ar eas wher e t he r oad i s par t of a t hr ough hi ghway, i t i snot necessar y t o appl y a hi gher st andar d wi t hi n t he ar ea t han exi st sf or t he r oadway out si de t he ar ea, pr ovi ded mi ni mum par k r oad st andardshave been met .

Bi keways

I f bi cycl i ng i s encour aged, consi der at i on must be gi ven t o pr ovi di ngsaf e t r avel ways. Separat e bi keways ar e nor mal l y t he saf estal t er nat i ve and shoul d be consi der ed. Wher e t hi s i s not pr act i cal ,and wher e a wi der r oad sect i on can be accommodat ed, shoul der ar eas may

be i mpr oved t o pr ovi de reasonabl e separ at i on of bi cycl es f r om hi gher -speed t r af f i c. Shoul der areas i nt ended f or bi cycl e use shoul d pr ovi de4 f eet of wi dt h per di r ect i on of t r avel and shoul d be smoot h sur f aced,and del i neat ed and marked t o i ndi cat e t he usage. Two- way bi cycl et r af f i c on t he same shoul der shoul d not be al l owed. On l ow- vol ume,l ow- speed r oads, t he shar i ng of t r avel l anes may be consi dered.

Sur f ace Type

The t ype of r oadway sur f ace t o be used i s det er mi ned by t he desi r edvi sual appear ance, t he vol ume and composi t i on of t r af f i c,

envi r onment al consi der at i ons, soi l condi t i ons, avai l abi l i t y and costof mat eri al s, and t he ext ent and cost of mai nt enance. Tabl e 10 showst he suggest ed sur f ace t ypes f or var i ous desi gn vol umes. Hi gh vol umet r af f i c j ust i f i es hi gh- t ype pavement s wi t h smoot h r i di ng qual i t i es andgood non- ski d pr oper t i es i n al l weat her . Most par k r oads shoul d havea sur f ace whi ch wi l l r et ai n t he cr oss- sect i on, whi ch wi l l adequat el ysuppor t t he pl anned vol ume and wei ght s of vehi cl es wi t hout f ai l ur e t okeep non- r out i ne mai nt enance t o a mi ni mum, and whi ch wi l l behar moni ous wi t h t he par k envi r onment .

Sur f ace Cr own

Sur f ace cr oss- sl ope must be pr ovi ded t o ensur e adequat e dr ai nage.However , excessi ve sur f ace sl opi ng can cause st eer i ng di f f i cul t i es.Cr oss- sl ope f or paved sur f aces shoul d r ange f r om 0. 01 t o 0. 03 f t / f t .For unsur f aced di r t or gr avel r oads, a cr oss- sl ope r angi ng f r om 0. 04t o 0. 06 f t / f t shoul d be pr ovi ded t o al l ow adequat e dr ai nage. On one-l ane roads wi t h l ow- t ype sur f aces, a crown woul d not usual l y bepr ovi ded. Roads of t hi s t ype shoul d be sl ope- gr aded t o pr ovi de f orpr oper dr ai nage.


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Roadsi de Sl opes and Dr ai nage

Where t er r ai n condi t i ons and park r esour ces per mi t , backsl opes,f or esl opes, and r oadsi de dr ai nage channel s shoul d have gent l e, wel l -r ounded t r ansi t i ons whi ch wi l l be achi eved t hr ough sl ope r oundi ng.Gener ous r oundi ng at t he t op of backsl opes i s especi al l y i mpor t ant t omi ni mi ze er osi on and ensur e l ong t er m st abi l i t y and r eveget at i on of cut sl opes. Each end of a cut - or - f i l l - sl ope shoul d be war ped t opr ovi de a pl easi ng appear ance. Fl at t er f or esl opes ar e gener al l y mor est abl e and f aci l i t at e r eveget at i on. The maxi mum r at e of f or esl opedepends on t er r ai n condi t i ons and t he st abi l i t y of soi l s as det er mi nedby l ocal exper i ence. I n deser t count r y wher e f i l l - sl opes do notveget at e r eadi l y, embankment s or sl opes shoul d be over l ai d or" pai nt ed" wi t h r ock or soi l of mat chi ng col or .

The di t ch f or esl ope used i n desi gn shoul d be r el at ed t o desi gn speed,t ype of t er r ai n, soi l t ypes, and r esour ce management consi der at i ons.Pref er abl y t he di t ch f oresl ope shoul d be 6: 1 f or ur ban par kways and

4: 1 f or Cl ass I Par k Roads . The f i r s t 10 f eet of t he f i l l s l opeshoul d al so be 4: 1 where pr act i cabl e t o pr ovi de emergency pul l of f ,yet di scour age random par ki ng.

Cut sect i ons shoul d be desi gned t o pr ovi de f or adequat e di t ches orot her dr ai nage f eat ur es t o ensur e posi t i ve dr ai nage. The di t ch mustbe l ar ge enough t o accommodat e t he desi gn f l ows and deep enough t opr ovi de f or sat i sf act or y dr ai nage of t he pavement base. I nappr opr i at e cases, under dr ai ns shoul d be used t o l essen i mpact s. I nt he case of r ock cut s, dr i l l hol es or t ool mar ks shoul d not be vi si bl ef r om t he r oadway.

Dr ai nage st r uct ur es, channel s, and di t ches must be hydr aul i cal l ydesi gned based on sound pr i nci pl es of hydr ol ogy and based on t her equi r ed consi der at i ons of t he ef f ect on f l oodpl ai ns.

Guar dr ai l / Gui der ai l

Guar dr ai l s or guar dwal l s are bar r i er s i nt ended t o redi r ect an er r antvehi cl e, t hus pr event i ng i t f r om hi t t i ng a r oadsi de or medi an hazar d.Gui der ai l s, qui dewal l s or gui de post s are i nt ended onl y t o del i neat et he roadway, or t o warn of r oadsi de hazar ds.

Guar dr ai l or guar dwal l s shoul d be i nst al l ed at poi nt s of unusualdanger such as shar p cur ves and st eep embankment s, par t i cul ar l y att hose poi nt s t hat ar e unusual compared wi t h t he overal lchar act er i st i cs of t he r oad. The cri t er i a used f or war r ant i ngguar dr ai l i nst al l at i on on hi gh- speed, hi gh- vol ume hi ghways do notappl y t o t he l ow- speed, l ow- vol ume t r af f i c condi t i ons on most par kr oads.


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I n addi t i on, pl acement and desi gn of bot h guar dr ai l and gui der ai lshoul d be as consi st ent as possi bl e f or bot h saf et y and appearancet hr oughout t he l engt h of a par t i cul ar r oadway. Choi ce of mat er i al sand desi gn shoul d be sensi t i ve t o t he set t i ng or envi r onment . I n snowcount r y, desi gn and l ocat i on shoul d r ecogni ze snow- r emoval met hods.

Cur bs

Except wher e necessary t o cont r ol t r af f i c or dr ai nage or t o pr ovi def or r oad wi deni ng, t he use of bar r i er cur bs on r oadways shoul d beavoi ded f or saf et y, economy and si mpl i ci t y. Where bar r i er curbs ar econt i nuous al ong a l ow speed hi ghway, t hey shoul d be of f set at l east 1f oot and pr ef er abl y at l east 2 f eet f r om t he edge of t r af f i c l ane andso car r i ed acr oss al l st r uct ur es. Bar r i er cur bs i nt r oduced on br i dgesor i nt er mi t t ent l y el sewher e shoul d be of f set at l east 2 f eet andpr ef er abl y 3 f eet .


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RESURFACI NG, RESTORATI ON & REHABI LI TATI ON PROJ ECTS

The pr i mar y pur pose of t he 3- R wor k t he Nat i onal Par k Servi ce wi l lunder t ake i s t o pr eser ve and ext end t he ser vi ce l i f e of par k r oads andt o enhance t hei r saf et y ( 23 U. S. C. 109( o) ) . Par k r oads on whi chgeomet r i es were est abl i shed several decades ago ar e capabl e i n mosti nst ances of pr ovi di ng saf e, usef ul ser vi ce. I n such cases, mi nori mprovement s wi l l make t hose r oads ser vi ceabl e f or many mor e year s,and t he compl et e r econst r uct i on whi ch woul d be r equi r ed on such r oadst o meet cur r ent st andar ds woul d be pr ohi bi t i vel y cost l y andenvi r onment al l y obj ect i onabl e.

A pr i mar y consi der at i on i n t he devel opment of 3- R pr oj ect s i sappl i cat i on of cr i t er i a whi ch wi l l al l ow t he necessar y f l exi bi l i t y toadj ust t o act ual f i el d condi t i ons. Consequent l y, t he geomet r i ci nf or mat i on t hat f ol l ows i s gener al l y t he mi ni mum consi der edaccept abl e. On 3- R wor k, t he i nt ent shoul d be t o i mpr ove above t hese

mi ni mums, wher e f easi bl e, and t o ensure t he hi ghest l evel of saf et ypossi bl e wi t hi n exi st i ng condi t i ons and const r ai nt s.

Gui dance f or 3- R pr oj ect s can be f ound i n FHWA' s Di r ect FederalManual , 3( C) ( 1) , Appendi x I , "Di r ect Feder al Geomet r i c Desi gn Cr i t er i af or Non- Fr eeway 3- R Pr oj ect s. "

Tr af f i c Vol ume - 3- R pr oj ect s ar e under t aken pr i mar i l y t o meetspeci f i c cur r ent needs . Wher e s i gni f i cant l evel s of r ehabi l i t at i onare i nvol ved, a desi r abl e desi gn vol ume shoul d be est abl i shed t hr oughmanagement deci si ons based on a 5- or 10- year t r af f i c f orecast .

Desi gn Speed - Roads s chedul ed f or 3- R wor k shoul d be eval uat ed basedon t he desi r abl e desi gn speed whi ch woul d accommodat e t he cur r entr unni ng speed, but a mi ni mum desi gn speed shoul d not be est abl i shed.I t i s essent i al , when consi der i ng a pr oj ect f or a sect i on of par kr oad, t hat t he geomet r i c condi t i ons beyond t he por t i on t o be i mpr ovedal so be eval uat ed and consi dered t o obt ai n uni f ormi t y and t o achi eveconsi st ency i n desi gn over t he ent i r e r out e. Ever y at t empt shoul d bemade t o mai nt ai n a uni f or ml y saf e runni ng speed f or a si gni f i cantsegment of t he r oadway. Consi derat i on shoul d be gi ven t o pr ovi di ng at r ansi t i on bet ween por t i ons of a roadway havi ng di f f er ent desi gnspeeds.

Pavement and Shoul der Wi dt hs - The cr i t eri a f or r oadway cr oss- sect i onsest abl i shed f or new const r uct i on and r econst r uct i on appl y t o 3- Rpr oj ect s, wher e f easi bl e.


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Gr ades, Cur vat ur e and Si ght Di st ance - These geomet r i c f eat ur es woul dusual l y requi r e an ol der r oad t o be r econst r uct ed, i f cur r entst andar ds were t o be achi eved, and coul d not nor mal l y be achi eved wi t h3- R wor k. The l evel of r econst r uct i on necessar y t o sat i sf y t hesecr i t er i a mi ght al so cause i mpact s on sur r oundi ng ar eas whi ch t heSer vi ce woul d deem i nappr opr i at e.

Dur i ng t he pr oj ect pl anni ng phase, however , al l hazar dous l ocat i onsal ong a r oadway shoul d be i dent i f i ed and acci dent r ecords shoul d beanal yzed t o det er mi ne i f r oadway f eat ur es are cont r i but i ng t oacci dent s. I f acci dent s r el at e t o gr ade, cross- sect i on, cur vat ur e orsi ght di st ance, consi der at i on shoul d be gi ven t o r econst r uct i oni mpr ovement s at cri t i cal l ocat i ons ( and/ or t o cont r ol of vehi cul art ypes and speeds, i mpr oved si gni ng, et c. )

Gener al l y, however , t he pr evi ousl y exi st i ng geomet r i c f eat ur es ( suchas gr ade, cur vat ur e and si ght di st ance) wi l l be r et ai ned on 3- Rpr oj ect s. I n such cases, each ver t i cal and hor i zont al cur ve shoul d be

checked f or st oppi ng si ght di st ance t o det er mi ne i f i t i s l ess t hant hat r equi r ed f or saf et y at t he post ed speed. I f so, advi sor y l i mi t edsi ght di st ance si gns gi vi ng t he appr opr i at e speed shoul d be i nst al l ed.I n some i nst ances, wher e encr oachment of veget at i on has i mpai r edor i gi nal si ght di st ance, appr opr i at e pr uni ng or r emoval shal l beaccompl i shed.

Br i dges - Appr oaches f or nar r ow br i dges ( i ncl udi ng one- way br i dges)shoul d be si gned and del i neat ed i n accor dance wi t h MUTCD.

Hi st or i c St r uct ur es - A number of park r oads and parkways, or

st r uct ur es on t hem ( e. g. br i dges, wal l s and over l ooks) ar e hi st or i c i nt hemsel ves, and ar e i n some i nst ances l i st ed on t he Nat i onal Regi st er .Pr eser vat i on or r est or at i on may be t he onl y opt i on f or such hi st or i cr oadways or st r uct ur es.


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STRUCTURES, SI GNI NG 6 MAI NTENANCE

St r uct ur es

The engi neer i ng desi gn of br i dges, cul ver t s, wal l s, t unnel s, andanci l l ary s t r uct ur es s houl d be i n accor dance wi t h AASHTO St andar dSpeci f i cat i ons f or Hi ghway Br i dges. The desi gn pr ocess shoul d bemul t i - di sci pl i nar y t o addr ess aest het i c, hi st or i cal , and envi r onment alconsi der at i ons.

The mi ni mum desi gn l oadi ng f or new r oadway br i dges shoul d be H- 15.Hi gher desi gn l oadi ngs may be appr opr i at e, dependi ng on use. Thever t i cal cl ear ance at underpasses shoul d be at l east 14 f eet above t heent i r e r oadway wi dt h. The cl ear r oadway wi dt hs f or new andr econst r uct ed br i dges shoul d desi r abl y be a mi ni mum of t he t r avel edway pl us shoul der s pl us f our f eet ( 2 f eet on each si de) .

Br i dge r ai l i ngs f or Cl ass I I t hr ough V r oads shoul d be desi gned f orl ow vol umes and speeds and t o per mi t l at er al sceni c vi ewi ng, i f appr opr i at e. Br i dge r ai l i ngs shoul d be l ocat ed coi nci dent wi t hbar r i er cur bs except wher e si dewal ks ar e pr ovi ded.

Si gni ng and Mar ki ng

Al t hough saf et y and ef f i ci ency of operat i on depend t o a maj or ext enton t he geomet r i c desi gn of a r oad, t hey shoul d be suppl ement ed byst andar d si gni ng and mar ki ng t o pr ovi de appr opr i at e t r af f i c cont r oland saf et y and t o pr ovi de i nf or mat i on t o dr i ver s. The Manual on

Uni f or m Traf f i c Cont r ol Devi ces ( MUTCD) , as suppl ement ed by t heNat i onal Par k Ser vi ce Si gn Manual , cont ai ns det ai l s r egar di ng desi gn,l ocat i on, and appl i cat i on of r oad si gns and mar ki ngs as t hey appl y t opark r oads and par kways. Appl i cat i on of st andar d si gni ng and pavementmar ki ngs shal l be i ncor por at ed as par t of t he desi gn pr ocess. Dur i ngconst r uct i on, pr oj ect t r af f i c cont r ol shal l be pr ovi ded by t hecont r act or , i ncl udi ng er ect i on and mai nt enance of al l necessarybar r i cades; sui t abl e and suf f i ci ent l i ght s, as appr opr i at e; and dangersi gnal s, si gns and ot her t r af f i c cont r ol devi ces i n conf or mi t y wi t h apr oj ect t r af f i c cont r ol pl an and wi t h Par t VI of t he MUTCD.

Mai nt enance

Road desi gn i s but one component i n t he over al l management of r oadf aci l i t i es, and must be consi der ed i n t hi s l i ght as par t of acont i nui ng pr ogr am of r oad and br i dge f aci l i t i es management andoper at i ons. Thi s pr ocess of r oad management commences wi t h advancepl anni ng and ext ends al l t he way t hr ough mai nt enance and oper at i on.


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GLOSSARY OF SELECTED TERMS

AASHTO - Abbr evi at i on f or Ameri can Associ at i on of St at e Hi ghway and Tr anspor t at i on Of f i ci al s.

ADT - cf . "Aver age Dai l y Tr af f i c" .

Aesthet i cs - A br anch of phi l osophy deal i ng wi t h beaut y and t hebeaut i f ul and j udgment s of t ast e concer ni ng t hem. I n hi ghwayengi neer i ng, aest het i c j udgment s have t o do pr i mar i l y wi t h t heappear ance of t he hi ghway or r oad as a whol e, i ncl udi ng t her oadsi de and i t s r el at i onshi p t o t he nat ur al and cul t ur alenvi r onment t hr ough whi ch i t passes.

Average Dai l y Traff i c ( ADT) - The average 24- hour vol ume, bei ng t het ot al vol ume dur i ng a st at ed per i od di vi ded by t he number of daysi n t hat peri od, normal l y a year or t he number of days t he r oad i sact ual l y open t o publ i c t r avel .

Average Runni ng Speed - For al l t r af f i c, or a component t her eof , t hesummat i on of di st ances t r avel ed di vi ded by t he summat i on of r unni ng t i mes.

Backsl ope - I n cut s, t he sl ope f r om t he bot t om of t he di t ch t o t he t opof t he cut .

Bri dge - A st r uct ur e exceedi ng 20 f eet cl ear span measur ed al ong t hecent er l i ne of t he r oadway, whi ch car r i es t r af f i c over awat er cour se or openi ng.

Broken Back Curve - An ar r angement of curves i n whi ch a shor t t angentseparat es t wo cur ves i n t he same di r ect i on.

Capaci ty - The maxi mum number of vehi cl es whi ch has a r easonabl eexpect at i on of passi ng over a gi ven sect i on of l ane or r oadwaydur i ng a gi ven t i me per i od under pr evai l i ng r oadway and t r af f i ccondi t i ons.

Center l i ne - ( 1) For a t wo- l ane r oad, t he cent er l i ne i s t he mi ddl e of t he t r avel ed way; and f or a di vi ded r oad, t he cent er l i ne may bet he cent er of t he medi an. For a di vi ded r oad wi t h i ndependentr oadways, each r oadway has i t s own cent er l i ne. ( 2) The def i nedand sur veyed l i ne shown on t he pl ans f r om whi ch r oad const r uct i oni s cont ro l l ed.

Cri t i cal Length of Grade - That combi nat i on of gr adi ent and l engt h of gr ade whi ch wi l l cause a desi gnat ed vehi cl e t o oper at e at somepr edet ermi ned mi ni mum speed. A l ower speed t han t hi s i sunaccept abl e and usual l y r equi r es t hat an auxi l i ar y cl i mbi ng l anebe pr ovi ded f or sl ow- movi ng vehi cl es.


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Cross Sect i on - The t r ansver se pr of

Documents

Park Road Std