Real-World Gaseous Emissions from Vehicles Fueled with Liquefied Petroleum Gas and Gasoline in a Plateau City

To study the real driving emissions of vehicles fueled with liquefied petroleum gas (LPG) and gasoline in plateau city, experimental investigations were performed on a LPG taxi and a gasoline vehicle in Lhasa using a portable emission measurement system (PEMS). The results reveal that the CO2, CO, NOx and HC emission factors of the LPG taxi are 147.38, 8.66, 1.96 and 0.28 g/km, whereas those of the gasoline vehicle are 217.35, 1.63, 0.38 and 0.04 g/km. The emissions show a strong relationship with the driving mode, which is affected considerably by traffic conditions and driving behaviors; especially, acceleration contributes a significant proportion of pollutant emissions. Furthermore, as speed increases, the gas emission factors of the LPG taxi decrease, whereas those of the gasoline vehicle initially decrease before increasing and then decreasing again. This pattern differs from those identified by previous investigations carried out in low-altitude areas. The emission rates of both vehicles are low and change slightly when vehicle specific power (VSP) is below 0. Afterward, these rates show an initially increasing trend and then decrease as VSP increases. These results may provide a base reference for use in formulating emission inventories and strategies for controlling vehicle emissions in plateau cities.