Motor　vehicles　are　recognised　as　important　contributors　to　urban　air　pollution.　However,　few　studies　have　focused　on　their　contribution　from　the　point　of　view　of　regional　transport.　To　address　this　gap,　the　validated　WRF-CAMx-PSAT　modelling　system　was　applied　to　quantitatively　evaluate　the　impact　of　vehicular　emissions　on　air　pollution　in　the　Beijing-Tianjin-Hebei　(BTH)　region　of　China　in　2014.　We　found　that　although　motor　vehicle　is　a　near-surface　source,　it　can　significantly　influence　the　air　quality　through　regional　transmission,　especially　with　respect　to　atmospheric　PM2.5　and　NO3-　during　haze　days.　The　fraction　of　non-local　emissions　to　the　overall　vehicular　emission　contribution　was　45.2%　and　60.3%　for　PM2.5　and　NO3-,　respectively.　Furthermore,　the　regional　transport　of　vehicular　emissions　played　an　increased　significant　role　in　contributing　toward　air　pollution　on　haze　days.　The　contribution　of　non-local　vehicular　emissions　to　atmospheric　PM2.5　and　NO3-　from　non-haze　to　haze　days　increased　by　38%　and　27%,　respectively.　An　8.01　times　change　in　the　per　unit　(10(4)　ton)　vehicular　emission　contribution　(PVEC)　of　non-local　emissions　from　non-haze　to　haze　days　for　NO3-　indicated　that　the　control　of　non-local　vehicular　emissions　can　be　more　effective　for　the　mitigation　of　NO3-　pollution,　as　compared　to　the　mitigation　of　undifferentiated　emissions　from　different　sources.　An　obvious　power　function　relationship　was　found　between　the　PVEC　and　transport　distance.　Attenuation　index　was　defined　to　analyse　the　degree　of　attenuation　of　pollutants　with　distance.　An　obvious　decrease　in　the　attenuation　coefficient　from　non-haze　to　haze　days　for　NO3-　indicated　that　the　regional　transport　of　NO3-　was　more　prominent　on　haze　days　from　vehicular　emission.　Thus,　this　study　can　provide　new　knowledge　for　understanding　the　environmental　impact　of　vehicular　emissions.　In　addition,　the　results　can　provide　a　scientific　basis　for　formulating　effective　regional　coordination　control　strategies　for　air　pollution.　(C)　2021　Published　by　Elsevier　B.V.