In　this　study,　a　new　approach　combining　the　environment　monitoring,　model　simulation　and　source　apportionment　methods　was　proposed　to　investigate　the　impact　of　vehicular　emissions　on　the　PM2.5　pollution.　The　method　can　identify　the　contributions　of　various　emission　sources　to　both　the　primary　and　secondary　particles.　A　case　application　was　conducted　in　Beijing,　China.　An　intensive　monitoring　covering　the　period　of　December　2010　to　January　2012　was　conducted　to　obtain　the　detailed　chemical　components　proportions　in　the　total　PM2.5.　The　vehicular　emission　contributions　(VECs)　to　primary　organic　aerosols　(POA),　element　carbon　(EC),　SO2,　NOX,　NH3,　elements　and　VOC　were　estimated　based　on　the　MM5-CMAQ　simulation,　factor　analysis　and　references　investigation.　The　VECs　to　different　components　and　to　the　total　PM2.5　were　then　calculated.　Results　showed　that　there　was　no　clear　difference　in　the　total　VECs　of　different　seasons.　The　annual　average　contribution　ratio　was　approximately　22.5　+/-　3.5%.　Among　all　the　chemical　species,　nitrate　and　SOA　accounted　for　the　highest　contribution　percentages.　In　addition,　the　influence　of　road　dust　on　the　PM2.5　pollution　was　also　simulated　using　the　MM5-CMAQ　modeling　system.　It　is　indicated　that　the　road　dust　contributed　approximately　4.9　+/-　1.3%　of　the　total　PM2.5　on　an　annual　average.　Considering　both　the　contributions　from　motor　vehicles　and　road　dust　emissions,　the　annual　average　direct　contributions　from　road　transport　to　the　PM2.5　in　Beijing　was　approximately　27.4　+/-　4.8%.　Crown　Copyright　(C)　2013　Published　by　Elsevier　Ltd.　All　rights　reserved.