Urban　expressway,　as　the　main　skeleton　of　the　road　network,　is　the　aorta　between　urban　regions　and　urban　external　traffic　communication,　but　also　bears　the　commuter　channel.　It　makes　a　large　amount　of　traffic　flow　into　the　expressway,　resulting　the　congestion　in　the　expressway　in　many　big　cities,　including　Beijing.　Taking　the　Beijing　southwest　third　ring　expressway　for　example,　a　simulation　model　was　built　using　Paramics.　The　simulation　model　was　pre-evaluated　before　and　after　the　bus　lanes　set,　and　the　model　was　post-evaluated　to　verify　the　validity　of　the　model　after　the　bus　lanes　were　implemented,　it　has　important　theoretical　and　practical　value.　(C)　2016　Published　by　Elsevier　Ltd.