[Emission Characteristics of Vehicles from National Roads and Provincial Roads in China].

In recent years, with the rapid increase in automobile volume, vehicle emissions have become one of the major emission sources of urban air pollution in China. In China, most of the national and provincial roads have been the channels that connect different cities. Up until 2015, the length of national and provincial roads have reached 1.85×10 km and 3.29×10km, respectively, accounting for 13% of the mileage of all classified highways. Therefore, active research on vehicle emissions from national and provincial roads between cities in China is of great significance. Few studies have been conducted on air pollutant emissions from intercity vehicles. In this study, emission characteristics of intercity vehicles were investigated based on traffic monitoring data and the "calculation guide of air pollutant emission for road vehicles". The results showed that the CO, NO, PM, and HC emissions accounted for 4.5%, 27.9%, 14.4%, and 7.7% of national vehicle emissions, respectively. There were significant differences in emission contributions among different types of intercity vehicles. Heavy trucks were major contributors to NO, PM, and PM emissions and motorcycles contributed most to CO and HC. Furthermore, there were significant differences in emission contributions of vehicle types on different road types; the major contributor of CO and HC emissions was small passenger cars on expressways. Motorcycles were the main contributors to CO and HC emissions on ordinary roads.