Panels a and b show the well-to-wheels GHG emissions for light- and heavy-duty vehicles, respectively, in China. Blue bars show the WTW GHG emissions without CH4 contribution. Green and orange bars are the CO2 equivalents of WTP CH4 emissions and CH4 emissions from NGVs (a GWP of 30 over a time-scale of 100 years is used for CH4 from fossil fuel consumption according to IPCC AR5)12. For cars and buses, NGVs may not bring GHG emission mitigation. NG trucks that meet China VI standard have lower GHG emissions compared to diesel trucks. The black error bars indicate high and low estimates derived using error propagation of uncertainties of multiple input parameters (e.g., life-cycle GHG emissions, CH4 emission factors, and fuel consumptions). Uncertainty estimates (standard deviation, S.D.) of individual parameters are listed in Supplementary Tables 1, 6, 7, and 11. Source data are provided as a Source Data file.