Together, diesel light and heavy-duty vehicles were responsible for almost all PM emissions, 80% of SO
emissions and 55% of NO emissions,while they accounted for only 4% of CO emissions. CNG light-duty vehicles were the main emitters of CH
and N
NV GHG CO2 CH4 N2O CO NMVOC NOX SO2 PM
O, accounting for more than 70% in both cases.