There　is　mounting　concern　about　low-carbon　travel　in　order　to　reduce　traffic　congestion,　improve　environmental　quality　and　save　energy.　Meanwhile,　the　public　bicycle　has　been　promoted　worldwide　as　an　energy-efficient　and　non-polluting　travel　mode.　Based　on　the　determination　of　carbon　emissions　factors,　this　paper　studied　the　carbon　emissions　of　different　traffic　modes　and　different　traffic　conditions,　and　established　the　carbon　emissions　reduction　model　of　public　bicycles.　Taking　Beijing　as　an　example,　on　the　basis　of　thorough　investigation　and　research,　this　study　calculated　the　carbon　emissions　reduction　of　Beijing　public　bicycles　in　July　2013.　The　purpose　of　this　paper　was　to　quantify　the　public　bicycle＇s　contribution　to　the　environment　and　demonstrate　whether　the　public　bicycle,　as　the　low-carbon　travel　mode　promoted　by　the　government,　was　a　more　cost　efficient　solution.　©　2014　American　Society　of　Civil　Engineers.