Real-world emissions in a high-altitude city: A comparison between LPG and gasoline- fueled cars

To study the real driving emissions characteristics of light-duty vehicles fueled with liquefied petroleum gas (LPG) and gasoline in the high-altitude city, experimental investigations were performed on two LPG taxis and three gasoline passenger cars in Lhasa using a portable emission measurement system (PEMS). The results reveal that the emission factors of CO2, CO, NOx, and HC of LPG taxis are (159.19±11.81), (18.38±9.73), (1.53±0.46), and (1.27±0.99) g/km, and those of gasoline cars are (223.51±23.1), (1.51±0.68), (0.27±0.16), and (0.06±0.04) g/km, respectively. The emissions show strong relationships with driving modes, which are considerably affected by driving behaviors. Furthermore, as vehicle speeds increase, the emission factors of both LPG taxis and gasoline cars decrease. The emission rates of both types of vehicles are low and change slightly at vehicle specific power (VSP) of 0 kW/t or below; after that, these rates slowly increase initially, and then increase rapidly with VSP increasing. These results may provide a base reference for use in formulating emission inventories and strategies for controlling vehicle emissions in high-altitudes.