基于ES-VSP分布的交通状态对公交车动态排放的影响

为评估不同交通状态下公交车运行特征和排放水平的差异，现场采集广州市B9、226线路公交车的逐秒GPS数据，以ES-VSP（发动机负荷-机动车比功率）分布表征畅通、轻度拥堵和中度拥堵下的公交车运行特征，结合IVE（international vehicle emission）模型求得公交车平均排放因子并分析其差异.结果表明:①所测公交车的发动机低负荷区中bin11（-1.6 < ES ≤ 3.1，-2.9 kW/t ≤ VSP < 1.2 kW/t）频率范围为50.55%~83.39%，中度拥堵时bin 11频率是畅通时的1.1~1.3倍；② 3种交通状态下公交车的CO、VOC（运行产生的挥发性有机物）、VOC_evap（蒸发产生的挥发性有机物）、NO_x（氮氧化物）和PM（颗粒物）平均排放因子范围分别为7.63~11.40、0.26~0.46、0.68~1.56、0.32~0.51和0.72×10-2~1.28×10-2 g/km；③同种交通状态下，主干路公交车专用道和BRT车道的公交车的大部分污染物平均排放因子低于次干路混行车道、主干路混行车道，中度拥堵时主干路BRT车道的CO、VOC、VOC_evap、NO_x和PM平均排放因子相对其他道路最低，分别为7.66、0.27、0.87、0.32和0.75×10-2 g/km；④次干路混行车道、主干路混行车道的公交车污染物平均排放因子随交通状态愈加拥堵而增大，但畅通时主干路BRT车道的公交车行驶速度、加速度较高，导致CO平均排放因子较高，对应3种交通状态其比例为1.0:0.9:0.8.研究显示，交通状态对公交车运行和排放具有显著影响. 

Effects of Traffic States on Dynamic Emissions of Buses based on ES-VSP Distribution

In order to evaluate bus emissions in different traffic states, second-by-second GPS data of No.B9 and No.226 buses in Guangzhou were collected, and Engine Stress-Vehicle Specific Power(ES-VSP) distribution was used to characterize the bus operation conditions during free-flow, mild congestion and moderate congestion. Combining ES-VSP distribution and the International Vehicle Emission(IVE) model, the average emission factors of the buses were calculated, and the differences were analyzed. The results showed that frequencies of bin11 (-1.6 < ES ≤ 3.1, -2.9 kW/t ≤ VSP < 1.2 kW/t, representing low speed and acceleration) of the buses were between 50.55% and 83.39%, while the frequencies of bin11 of moderate congestion were 1.1-1.3 times those of free-flow. For various traffic states, the buses' average emission factor ranges of CO, VOC (volatile organic compounds emission from running), VOC_evap (volatile organic compounds emission from evaporation), NO_x (nitrogen oxide) and PM (particulate matter) were 7.63-11.40, 0.26-0.46, 0.68-1.56, 0.32-0.51 and 0.72×10-2-1.28×10-2 g/km, respectively. In the same traffic state, the bus average emission factors for ordinary bus lane or BRT lane of arterial road were mostly lower than those of mixed lane of secondary road or arterial road. The buses' average emission factors of CO, VOC, VOC_evap, NO_x and PM of BRT lane in moderate congestion state were 7.66, 0.27, 0.87, 0.32 and 0.75×10-2 g/km respectively, which were lower than those of the other three types of lane. With a more congested traffic state in mixed lane of secondary road or arterial road, the bus average emission factors increased. However, the higher speed and acceleration of buses on free-flow BRT lanes made the CO average emission factor higher. The CO average emission factor ratio was 1:0.9:0.8, corresponding to the three traffic states. The research showed that traffic states have an important influence in operation and emission of buses.