Road routes in South Australia assist drivers navigating roads in urban, rural, and scenic areas of the state. Today, all numbered routes in the state are allocated a letter (M, A or B) in addition to a one, two or three digit number, denoting different levels of significance. The route system includes officially designated highways, urban freeways and arterial roads, and other important cross-state roads that have not been declared highways.
History Route numbers have been allocated to South Australia's roads since 1955, with the introduction of National Routes across all states and territories in Australia, symbolised by a white shield with black writing; National Route 1 ('Highway 1') was one of the best-known numbered national routes, due to its fame for circumnavigating the continent.
In 1974, the National Highway network was defined, which allowed some existing National Routes to be upgraded to National Highways. These were marked with the same shield design as the National Routes, except for their gold-on-green colouring and the word NATIONAL added across the top. Unlike many other states, South Australia never adopted State Routes, although it allowed two Victorian rural State Routes to cross the border and terminate in locations within 20 km of it when they were rolled out there in 1985.
In 1998, the state replaced its system of National Routes and National Highways with an alphanumeric route numbering system. Many existing numbered routes were allocated a letter (M, A or B) in addition to its number, with 'M' routes denoting freeways, 'A' routes denoting routes of state significance, and 'B' routes denoting routes of local significance. Instead of shields, route numbers are displayed as yellow text on green rectangular backgrounds, and has now become the sole route numbering system in the state. The changeover to alphanumeric routes was carried out from 1998 either by removing old "shield" coverplates installed on newer signs, or installing new alphanumeric coverplates on old shielded signs, adopting the same design as Victoria (which adopted its alphanumeric system a year previous). Trailblazers were introduced with alphanumeric routes in Adelaide's metropolitan area and the tourist areas of Victor Harbor and the Barossa Valley in 1998, with allocations extended to cover country areas in 1999. Former National Highways still retained their shield design (including NATIONAL markings) after conversion, but were modified in 2017 to remove them, bringing their design in line with the rest of the state.
Alphanumeric Routes All alphanumeric routes listed here are derived from the Government of South Australia's Location SA service.
M routes Roads allocated an M route are usually at least dual-carriageway motorways or expressways, with at least two lanes in each direction. These roads keep traffic moving and are likely to have no traffic lights and higher speed limits.
Route Component roads From Via To Length NotesM1South Eastern FreewayGlen OsmondMurray BridgePart of Highway 1:– western end re-aligned through Eagle on the Hill from Mount Barker Road to current alignment when freeway extension through the Heysen Tunnels opened in 2000– continues north west as along Glen Osmond Road beyond Adelaide– continues east as along Princes Highway to Tailem Bend– allocated in 1998, progressively being replaced by from 2017M2Northern ExpresswayGawlerHindmarshAllocated in 2016 (replacing )Northern ConnectorAllocated upon opening in 2020North–South Motorway – allocated through Wingfield (replacing ) when South Road Superway opened in 2014, progressively being replaced by from 2017– extended south to Hindmarsh (replacing ) when Torrens to Torrens section opened in 2018– to be extended further south eventually to Southern Expressway as further stages of the North–South Motorway are completed– continues south as along South Road to Southern Expressway at St MarysSouthern ExpresswaySt MarysNoarlunga Downs – southern end extended from Reynella to Noarlunga Downs when second stage opened in 2001– northern end extended from Darlington to St Marys when Darlington bypass opened in 2020– to be extended further north eventually to North–South Motorway as further stages are completed– continues north as along South Road to North–South Motorway at HindmarshNational Highway M20Northern ExpresswayVirginiaGawlerAllocated upon opening in 2010, replaced by when Northern Connector commenced construction in 2016
A routes Roads allocated an A route are main or arterial routes providing a high standard of driving conditions both across single- or dual-carriageway roads, linking to and from M roads and provide access to major towns and places of interest across metro and regional SA.
Route Component roads From Via To Length NotesA1SA/WA borderMedindiePart of Highway 1:– continues west as along Eyre Highway into WA eventually to Norseman– discontinuous across the Adelaide city centre, partially – allocated in 1998, progressively being replaced by from 2017EastwoodFrewvilleGlen Osmond – discontinuous across the Adelaide city centre, partially – eastern end along Mount Barker Road terminating in Crafers truncated to current alignment when South Eastern Freeway extension through the Heysen Tunnels opened in 2000– continues east as along South Eastern Freeway to Murray Bridge– allocated in 1998, progressively being replaced by from 2017Princes HighwayMurray BridgeSwanport BridgeTailem Bend – continues west as along South Eastern Freeway to Glen Osmond– continues south as along Princes Highway to Mount Gambier– allocated in 1998, progressively being replaced by from 2017Princes HighwayMount GambierSA/Vic border – continues west as along Princes Highway to Tailem Bend– continues east as along Princes Highway into Victoria eventually to GeelongA2South RoadHindmarshSt Marys – allocated from Regency Park to Darlington (replacing ) when South Road Superway opened in 2014– northern end truncated to Hindmarsh (replaced by ) when Torrens to Torrens section of North–South Motorway opened in 2018– southern end truncated to St Marys (replaced by ) when Darlington bypass of Southern Expressway opened in 2020– continues north as along North–South Motorway to Gawler– continues south as along Southern Expressway to Noarlunga DownsA3Cross RoadPlymptonUnley ParkGlen OsmondA5Anzac HighwayKeswickPlymptonGlenelgNorthern end truncated from Adelaide to Keswick when City Ring Route re-aligned in 2017A6Mile EndBrooklyn ParkWest BeachEastern end truncated from Adelaide to Mile End when City Ring Route re-aligned in 2017A7HindmarshPort AdelaideA8Dukes HighwayTailem BendSA/Vic border – continues east as along Western Highway into Victoria eventually to Buangor– concurrency with along Dukes Highway from Lowan Vale to Bordertown– allocated in 1998, progressively being replaced by from 2017A9Port AdelaideElizabeth ValeEastern end extended along Salisbury Highway and John Rice Avenue from Dry Creek to Elizabeth Vale (replacing /) when South Road Superway opened in 2014A10 GilbertonHoughtonContinues east as along North East Road to NuriooptaA11Kent TownSalisbury HeightsNorthern end re-aligned from Lower North East Road terminating in Houghton (replaced by ) to current alignment in 2021A13DarlingtonVictor Harbor – allocation along South Road, Salisbury Highway and John Rice Avenue terminating in Elizabeth Vale truncated to current alignment (replaced by / and ) when South Road Superway opened in 2014– concurrency with along Victor Harbor Road through Willunga Hill– allocated along South Road through Wingfield in 1998, replaced by in 2014, progressively being replaced by from 2017A14BeverleyDarlingtonA15AlbertonMaslin BeachSouthern end extended from Hallett Cove to Maslin Beach in 2021A16Outer HarborHoughtonGrand Junction RoadAllocated (from Regency Park to Northfield) in 1998, progressively being replaced by from 2017Lower North East RoadEastern end extended along Lower North East Road from Hope Valley to Houghton (replacing ) in 2021A17NorthfieldPaynehamGlen OsmondAllocated in 1998, progressively being replaced by from 2017A18ParalowieParafieldModburyA20 Gepps CrossSA/Vic border – continues east as along Sturt Highway into Victoria through Mildura, and into New South Wales eventually to Tarcutta– allocated in 1998, progressively being replaced by from 2017– western end along Main North Road terminating at Gepps Cross truncated to Gawler (replaced by ) when Northern Expressway opened in 2010, reverted to in 2017A21AdelaideNorth AdelaideAdelaideFormer City Ring Route, replaced by in 2017, listed clockwise from the western corner of Adelaide city centreA22Gepps CrossKilburnOvinghamA32Barrier HighwayGiles CornerSA/NSW border – continues east as along Barrier Highway into New South Wales to Nyngan– concurrency with along Barrier Highway through BurraHorrocks HighwayGiles CornerTarleeGawler BeltLater replaced by along Horrocks Highway, truncated to Giles CornerA52Main North RoadGepps CrossGawlerAllocated when Northern Expressway opened (replacing ) in 2010, reverted to in 2017A66Riddoch HighwayKeithMount GambierContinues south as along Riddoch Highway to Port MacDonnellA87Stuart HighwaySA/NT borderPort Augusta West – continues north as along Stuart Highway into NT eventually to Daly Waters– allocated in 1998, progressively being replaced by from 2017
B routes Roads allocated a B route are secondary or local arterial roads, These roads link to and from A and M roads and provide access to places of interest across metro and regional SA.
Route Component roads From Via To Length NotesB1Princes HighwayTailem BendMount GambierPart of Highway 1: – continues north as along Princes Highway to Murray Bridge– continues east as along Princes Highway into Victoria eventually to GeelongB10HoughtonNurioopta – continues west as along North East Road to Adelaide– concurrencies with: along North East Road through Chain of Ponds; along Torrens Valley Road through Birdwood; along Torrens Valley Road through Mount PleasantB12Mallee HighwayTailem BendSA/Vic border – continues east as along Mallee Highway into Victoria eventually to Piangil– concurrency with along Mallee Highway through PinnarooB19GawlerLyndochNuriootpaB23Main South RoadOld NoarlungaCape JervisRoute continues west over Backstairs Passage to Hog Bay Road on Kangaroo IslandPenneshawPelican LagoonKingscoteRoute continues east over Backstairs Passage to Main South Road on the South Australian mainlandB26Greenhill Road GlensideUraidlaBalhannah Allocated in 2019B27Kent TownMount Torrens Allocated in 2019 B28FullartonSummertownAllocated in 2019B29UnleyClarendonAllocated in 2020B31CampbelltownLyndochConcurrency with along North East Road through Chain of PondsB33StirlingStrathalbynB34WilliamstownMypongaConcurrencies with: along Victor Harbor Road through Willunga Hill; along Torrens Valley Road through BirdwoodB35Mount CrawfordMurray BridgeConcurrency with along Torrens Valley Road through Mount PleasantB36PalmerMannumMurray Bridge NorthB37Mount BarkerDelamereConcurrency with along Hindmarsh Road through Victor HarborB45StrathalbynLanghorne CreekWellington EastB55Murray BridgeBerriB56WinninowiePeterboroughConcurrencies with: along RM Williams Way from Orroroo to Black Rock; along Horrocks Highway through WilmingtonB57LoxtonCadgeeConcurrencies with: along Dukes Highway from Lowan Vale to Bordertown; along Mallee Highway through PinnarooB64Goyder HighwayCrystal BrookMonashConcurrencies with: along Barrier Highway through Burra; along RM Williams Way through Spalding; along Horrocks Highway through GulnareB66Riddoch HighwayMount GambierMount Schank