TheSydneyHarbourBridgeisthemaincrossingofSydneyHarbourcarryingvehicular,rail,andpedestriantrafficbetweentheSydneycentralbusinessdistrict(CBD)andtheNorthShore.ThedramaticwatervistaofthebridgetogetherwiththenearbySydneyOperaHouseisaniconicimageofbothSydneyandAustralia.ThebridgeiscolloquiallyreferredtoastheCoathangerbecauseofitsarch-baseddesign,althoughthisusageislessprevalentthanitoncewas.TheiconicBridgeiscelebratingits75thanniversaryin2007.

　　Thebridgewasthecity'stalleststructureuntil1967.AccordingtoGuinnessWorldRecords,itisthewidestlong-spanbridgeintheworldandisthelargeststeelarchbridgewiththetopofthebridgestanding134metresabovetheharbour.

　　Thebridge'stwoendsarelocatedatDawesPoint(inSydney'sRocksarea)andMilsonsPoint(inSydney'slowerNorthShorearea).Itcarriessixlanesofroadtrafficonitsmainroadway,twolanesofroadtraffic(formerlytwotramtracks)andafootpathonitseasternside,andtworailwaytracksandabicyclepathalongitswesternside.Thewesternsidebeing305mmlargerthattheeastside.

　　TheroadacrossthebridgeisknownastheBradfieldHighwayandisabout2.4km(1.5miles)long,makingitoneoftheshortesthighwaysinAustralia.(Theshortest,alsocalledtheBradfieldHighway,isfoundontheStoryBridgeinBrisbane).At48.8m(151.3feet)wide,itisthewidestlong-spanbridgeintheworld(GuinnessWorldRecords,2004).Thebridgedeckportionofthehighwayis1.15km(0.71miles)long.Itisconcreteandliesontrimmers(beamsthatrunalongthelengthofthebridge).Thetrimmersthemselvesrestonsteelbeamsthatrunalongthewidthofthebridge.Thetrimmersandbeamsarevisibletoboatsthatpassunderneaththebridge.

　　Thearchiscomposedoftwo28-panelarchtrusses.Theirheightsvaryfrom18m(55.8feet)atthecenterofthearchto57m(176.7feet)(besidethepylons).

　　Thearchspanis509m(1,559feet)andtheweightofthesteelarchis39,000tons.Thearch'ssummitis134m(415.4feet)abovemeansealevel,thoughitcanincreasebyasmuchas180mm(7in)onhotdaysastheresultofsteelexpandinginheat.Twolargemetalhingesatthebaseofthebridgeaccommodatetheseexpansionsandcontractionsandtherebypreventthearchfrombeingdamaged.Thesteelusedforthebridgewaslargelyimported.About79%camefromMiddlesbroughintheNorthEastofEngland,therestwasAustralian-made.ThegraniteusedwasquarriedinMoruya,NewSouthWales,andtheconcreteusedwasalsoAustralianmade.

　　Thetotalweightofthebridgeis52,800tonnes,andsixmillionhand-drivenrivetsholdthebridgetogether.TherivetsweremadeattheParkBridgeIronworksinLancashireEngland.

　　Thetwopairsofpylonsateachendareabout89m(276feet)highandaremadeofconcreteandgranite.Abutments,whichsupporttheendsofthebridge,arecontainedatthebaseofthepylons.Theypreventthebridgefromstretchingorcompressingduetotemperaturevariations.Otherwise,thepylonsservenostructuralpurposeandareprimarilytovisuallybalancethebridgeitself.Theywereoriginallynotpartofthedesignbutwereaddedlatertoallayconcernsaboutstructuralintegrity—ironically,asthepylonsdonotactuallytouchthebridge(exceptatroadlevel).Althoughinsertedintothedesignsfortheiraestheticvalue,allfourpylonshavenowbeenputtouse:amuseumandtouristcentr