Effect of low ambient temperature on fuel consumption and pollutant and CO2 emissions of hybrid electric vehicles in real-world conditions

► Experimental investigation on low ambient temperature emission performance of HEVs. ► HEVs feature reduced cold start extra emissions (CSEE) of regulated pollutants. ► HEV CSEE of CO2 and fuel consumption result mainly similar or selectively increased. ► No significant influence of low ambient temperature on hot HEV emissions observed. ► Initial battery SOC significantly influences HEV CSEE of CO2 and fuel consumption.