Interstate Highway Standards

7/25/2019 Interstate Highway Standards

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Interstate Highway standards

Standards for Interstate Highwaysin the United States are defned by the American Association o

State Highway and Transportation Ocials(AASHTO) in the pblicationA Policy on Design Standards -

Interstate System! "or a certain highwayto be considered an Interstate# it mst meet these constrction

re$irements or obtain awai%errom the "ederal Highway Administration!

An Interstate Highway nder constrction# with both directions o trac mo%ed to one side o the

roadway

I&'in ichigan# showing e*amples o non&interchange o%erpass signage in median# pcoming e*it

signage on right sholder# a +',-s o%erpass with height restriction signage# newly installed cable

median barrier# and parallel groo%ed pa%ement with sholder rmble strips

An Interstate Highway bridge with an asphalt o%erlay

Standards

These standards are# as o .ly /--0# as ollows1

Controlled access:All access onto and o2 the roadway is to

be controlledwith interchangesand grade separations(inclding railroadcrossings)! See3ist o gaps in

Interstate Highwaysor the ew cases that %iolate this rle! Interchanges shold pro%ide ll access

ramps are to be designed with the appropriate standards in mind! inimm interchange spacingshold be + mi (+!5 6m) in rban areasand 7 mi (!8 6m) in rral areas4 collector9distribtor roadsor

other confgrations that redce wea%ing can be sed in rban areas to shorten this distance!

Access control (rom ad:acent properties) shold e*tend at least +-- eet (7- m) in rban

areas and 7-- eet ('+ m) in rral areas in each direction along the crossroad rom the ramps!

Minimum design speed:inimm design speed o 0, mph (+/+ 6m9h) in rral areas# with

5, mph (+-, 6m9h) acceptable in rolling terrain# and as low as ,- mph (8- 6m9h) allowed

in montainosand rban areas!;citation needed allowed in montainos

areas and hilly rban areas!

Minimum number of lanes:At least two lanesin each direction# and more i necessary or an

acceptable le%el o ser%icein the design year# according to the crrent edition o AASHTO=sA Policy on

Geometric Design of Highways and Streets! ?limbing lanesand emergency escape rampsshold be

pro%ided where appropriate!
http://en.wikipedia.org/wiki/Interstate_Highwayshttp://en.wikipedia.org/wiki/Interstate_Highwayshttp://en.wikipedia.org/wiki/American_Association_of_State_Highway_and_Transportation_Officialshttp://en.wikipedia.org/wiki/American_Association_of_State_Highway_and_Transportation_Officialshttp://en.wikipedia.org/wiki/Highwayhttp://en.wikipedia.org/wiki/Waiverhttp://en.wikipedia.org/wiki/Waiverhttp://en.wikipedia.org/wiki/Federal_Highway_Administrationhttp://en.wikipedia.org/wiki/Interstate_94_in_Michiganhttp://en.wikipedia.org/wiki/Interstate_94_in_Michiganhttp://en.wikipedia.org/wiki/Controlled_accesshttp://en.wikipedia.org/wiki/Interchange_(road)http://en.wikipedia.org/wiki/Grade_separationhttp://en.wikipedia.org/wiki/Grade_separationhttp://en.wikipedia.org/wiki/Railroadhttp://en.wikipedia.org/wiki/List_of_gaps_in_Interstate_Highwayshttp://en.wikipedia.org/wiki/List_of_gaps_in_Interstate_Highwayshttp://en.wikipedia.org/wiki/Urban_areahttp://en.wikipedia.org/wiki/Collector/distributor_roadhttp://en.wikipedia.org/wiki/Design_speedhttp://en.wikipedia.org/wiki/Hillhttp://en.wikipedia.org/wiki/Mountainhttp://en.wikipedia.org/wiki/Urban_areahttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Sight_distancehttp://en.wikipedia.org/wiki/Curvaturehttp://en.wikipedia.org/wiki/Superelevationhttp://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/wiki/Grade_(slope)http://en.wikipedia.org/wiki/Lanehttp://en.wikipedia.org/wiki/Level_of_servicehttp://en.wikipedia.org/w/index.php?title=Design_year&action=edit&redlink=1http://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/wiki/Climbing_lanehttp://en.wikipedia.org/wiki/Runaway_truck_ramphttp://en.wikipedia.org/wiki/File:Interstate_25_Highway_Bridge_with_Asphalt_Overlay.jpghttp://en.wikipedia.org/wiki/File:Non_Interchange_Signage_with_Mileage_Signage.jpghttp://en.wikipedia.org/wiki/File:Interstate_196_Construction.jpghttp://en.wikipedia.org/wiki/American_Association_of_State_Highway_and_Transportation_Officialshttp://en.wikipedia.org/wiki/American_Association_of_State_Highway_and_Transportation_Officialshttp://en.wikipedia.org/wiki/Highwayhttp://en.wikipedia.org/wiki/Waiverhttp://en.wikipedia.org/wiki/Federal_Highway_Administrationhttp://en.wikipedia.org/wiki/Interstate_94_in_Michiganhttp://en.wikipedia.org/wiki/Controlled_accesshttp://en.wikipedia.org/wiki/Interchange_(road)http://en.wikipedia.org/wiki/Grade_separationhttp://en.wikipedia.org/wiki/Railroadhttp://en.wikipedia.org/wiki/List_of_gaps_in_Interstate_Highwayshttp://en.wikipedia.org/wiki/List_of_gaps_in_Interstate_Highwayshttp://en.wikipedia.org/wiki/Urban_areahttp://en.wikipedia.org/wiki/Collector/distributor_roadhttp://en.wikipedia.org/wiki/Design_speedhttp://en.wikipedia.org/wiki/Hillhttp://en.wikipedia.org/wiki/Mountainhttp://en.wikipedia.org/wiki/Urban_areahttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Sight_distancehttp://en.wikipedia.org/wiki/Curvaturehttp://en.wikipedia.org/wiki/Superelevationhttp://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/wiki/Grade_(slope)http://en.wikipedia.org/wiki/Lanehttp://en.wikipedia.org/wiki/Level_of_servicehttp://en.wikipedia.org/w/index.php?title=Design_year&action=edit&redlink=1http://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/wiki/Climbing_lanehttp://en.wikipedia.org/wiki/Runaway_truck_ramphttp://en.wikipedia.org/wiki/Interstate_Highways


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Minimum lane width:inimm lane width o +/ eet (7!55 m)! Also or most US and state

highways!

Shoulder width:inimm otside pa%ed sholderwidth o +- eet (7!-, m) and inside sholder

width o eet (+!// m)! @ith three or more lanes in each direction# the inside pa%ed sholder shold

be at least +- eet (7!-, m) wide! I trc6 trac is o%er /,- irectional esign Hor Bolme# sholders

at least +/ eet (7!55 m) wide shold be considered! In montainos terrain# 8 eet (/! m) otside

and eet (+!// m) inside sholders are acceptable# e*cept when there are at least or lanes in each

direction# in which case the inside sholders shold also be 8 eet (/! m) wide!

Pavement sloping:Ca%ement cross slopeo at least +!,> and preerably /> to ensre

proper drainageon straight sections! This can be increased to /!,> in areas o hea%y rainall! Sholder

cross slope shold be between /> and 5> bt not less than the main lanes!

3and slopes within the clear Doneshold be at most 1+ and preerably 51+ o

Eatter! Foadside barriersshold be sed or slopes o 71+ or steeper# in accordance with the crrent

edition o AASHTO=s Roadside Design Guide!

Median width:inimm medianwidth o 75 eet (++ m) in rral areas# and +- eet (7!- m) in

rban or montainos areas! To pre%entmedian&crossing accidents#gard railor.ersey barriershold

be installed in medians in accordance with the crrent edition o AASHTO=s Roadside Design Guide

based on trac# median width and crash history! @hen possible# median openings between paralle

bridges less than 7- eet ('!+ m) in width shold be dec6ed o%er4 otherwise barriers or gard rails

shold be installed to e*clde %ehicles rom the gap!

Recovery areas:Go f*ed ob:ects shold be in the clear reco%ery area#determined by the design

speed in accordance with the crrent edition oAASHTO=s Roadside Design Guide! @hen this is not

possible# brea6away spportsor barriers garding the ob:ects shall be sed!

Curb slope:Bertical crbsare prohibited! Sloping crbs are to be at the edge o the pa%ed

sholder# with a ma*imm height o +-- millimetres (7!' in)! The combination o crbs and gard railis

discoraged4 in this case the gard rail shold be closer to the road than the crb!

ertical clearance:inimm %ertical clearancender o%erhead strctres (inclding o%er the

pa%ed sholders) o +5 eet (!88 m) in rral areas and + eet (!/0 m) in rban areas# with allowance

or e*tra layers o pa%ement! Throgh rban areas at least one roting shold ha%e +5 eet (!88 m

clearances! Sign spports and pedestrian o%erpasses mst be at least +0 eet (,!+8 m) abo%e the road

e*cept on rban rotes with lesser clearance# where they shold be at least + t (-!7 m) higher than

other ob:ects! Hori!ontal clearance:nder or along a bridge shall be the ll pa%ed width o the rest o the road

ridges longer than /-- eet (5+ m) can be narrower# with a minimm o eet (+!// m) on both sides

o the tra%el lanes!

"ridge strength:Gew bridges are to ha%e at least S +8 (HS&/-) strctral capacity! @ea6er

bridges that can contine to ser%e the rote or /- more years are allowed to remain!

Additionally# e*isting bridges can remain i they ha%e at least +/ eet (7!55 m) lanes with +-

eet (7!-, m) otside and 7!, eet (+!-0 m) inside sholders! 3ong bridges are to ha%e at least 7!,
http://en.wikipedia.org/wiki/Shoulder_(highway)http://en.wikipedia.org/wiki/Shoulder_(highway)http://en.wikipedia.org/w/index.php?title=Directional_Design_Hour_Volume&action=edit&redlink=1http://en.wikipedia.org/wiki/Cross_slopehttp://en.wikipedia.org/wiki/Drainagehttp://en.wikipedia.org/wiki/Rainfallhttp://en.wikipedia.org/w/index.php?title=Clear_zone&action=edit&redlink=1http://en.wikipedia.org/wiki/Roadside_barrierhttp://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/wiki/Median_(highway)http://en.wikipedia.org/w/index.php?title=Median-crossing_accident&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Median-crossing_accident&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Median-crossing_accident&action=edit&redlink=1http://en.wikipedia.org/wiki/Guard_railhttp://en.wikipedia.org/wiki/Guard_railhttp://en.wikipedia.org/wiki/Jersey_barrierhttp://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/w/index.php?title=Clear_recovery_area&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Clear_recovery_area&action=edit&redlink=1http://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/w/index.php?title=Breakaway_support&action=edit&redlink=1http://en.wikipedia.org/wiki/Curb_(road)http://en.wikipedia.org/wiki/Guard_railhttp://en.wikipedia.org/wiki/Distancehttp://en.wikipedia.org/wiki/Urban_areahttp://en.wikipedia.org/wiki/Pavement_(material)http://en.wikipedia.org/w/index.php?title=HS-20&action=edit&redlink=1http://en.wikipedia.org/wiki/Factor_of_safety#Margin_of_safetyhttp://en.wikipedia.org/wiki/Shoulder_(highway)http://en.wikipedia.org/w/index.php?title=Directional_Design_Hour_Volume&action=edit&redlink=1http://en.wikipedia.org/wiki/Cross_slopehttp://en.wikipedia.org/wiki/Drainagehttp://en.wikipedia.org/wiki/Rainfallhttp://en.wikipedia.org/w/index.php?title=Clear_zone&action=edit&redlink=1http://en.wikipedia.org/wiki/Roadside_barrierhttp://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/wiki/Median_(highway)http://en.wikipedia.org/w/index.php?title=Median-crossing_accident&action=edit&redlink=1http://en.wikipedia.org/wiki/Guard_railhttp://en.wikipedia.org/wiki/Jersey_barrierhttp://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/w/index.php?title=Clear_recovery_area&action=edit&redlink=1http://en.wikipedia.org/wiki/AASHTOhttp://en.wikipedia.org/w/index.php?title=Breakaway_support&action=edit&redlink=1http://en.wikipedia.org/wiki/Curb_(road)http://en.wikipedia.org/wiki/Guard_railhttp://en.wikipedia.org/wiki/Distancehttp://en.wikipedia.org/wiki/Urban_areahttp://en.wikipedia.org/wiki/Pavement_(material)http://en.wikipedia.org/w/index.php?title=HS-20&action=edit&redlink=1http://en.wikipedia.org/wiki/Factor_of_safety#Margin_of_safety


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eet (+!-0 m) on each side o the tra%el lanes4 bridge railingshold be pgraded to crrent

standards i necessary!

#unnel clearance:Tnnelsshold in theory be e$i%alent to long o%ercrossings# bt becase o

cost the standards can be redced! Bertical clearance is the same as nder bridges# inclding the

pro%ision or alternate roting! @idth shold be at least eet (+7!+ m)# which consists o two +/

eet (7!55 m) lanes# +- eet (7!-, m) otside and , eet (+!,/ m) inside sholders# and /!, eet

(-!05 m) saety wal6ways on each side! I necessary to meet the dimensions o the approach# this can

be shited let or right! A redced width is acceptable de to high cost! In this case# the minimm width

is 7- eet ('!+ m)# with at least / eet (-!5+ m) more than the approach or the sm o the sholder

widths# bt at least / eet (0!7/ m) total# and at least +!, eet (-!5 m) on each side or a saety

wal6way! I there is no saety wal6way# a 7&oot (-!'+ m) o2set with a saety shape in the wall is

acceptable!

$xceptions

The standards ha%e been changed o%er the years# reslting in many older Interstates not conorming to

the crrent standards# and yet others are not bilt to standards becase to do so wold be too costly oren%ironmentally nsond!

Some roads were grandatheredinto the system! ost o these weretoll roadsthat were bilt beore the

Interstate system came into e*istence or were nder constrction at the time Cresidentwight

Jisenhowersigned the"ederal Aid Highway Act o +',5! The most notable e*ample is the Cennsyl%ania

Trnpi6e# which originally had a %ery narrow median that later re$ired the installation o a.ersey

barrierde to hea%y trac loads!

Interstate '7throgh "ranconia Gotch# Gew Hampshireis also a notable e*ception being a spe

twopar6way with a speed limit o , miles per hor!

Interstate 7,Jthrogh Saint Cal# innesotais an e*ample o a reeway that was not grandathered into

the system that is nonetheless an e*ception to standards! The reeway was not opened ntil +''-# has a

speed limit o , CH# and does not allow %ehicles weighing o%er '#--- ponds KB@! This is de to a

nmber o lawsits rom wealthy srronding homeowners# which hea%ily delayed and modifed the pro:ect

dating to the +'5-s!

Interstate 0,on the ac6inac ridgebetween St! Ignaceand ac6inaw ?ity# ichigan# is ndi%ided! The

bridge was designed beore the start o the Interstate Highway System# and it was grandathered into the

system!;+

Documents

Interstate Highway Standards