中文摘要：

使用车载排放测试系统测试了北京市4种不同技术路线的14辆国V车辆的实际道路排放情况。结果表明，氧化催化器（ DOC）能明显降低天然气公交车的CO排放，但其对THC的降排效果有待提高。采用EGR技术的天然气公交车在低速时NOx减排效果较柴油车好，但是高速时没有优势。使用SCR系统的柴油车CO和THC排放较低，但低速时NOx 排放较高。而天然气车由于排气温度较高，加装SCR系统后可有效降低NOx排放，效果最理想。天然气公交车的颗粒物质量排放远低于柴油车，但是由于稀释方式的影响，其核模态的颗粒物数量较多。

英文摘要：

The real world emissions from 14 State-V buses with four different after-treatment technologies are measured with portable emission measurement system. The results show that diesel oxidation catalyst can appar-ently reduce the CO emission of CNG-fueled buses, but its effect of reducing THC emission need to be improved. The CNG-fueled buses adopting EGR technology have a better emission reduction effects than diesel buses at low speed but there is no superiority at high speeds. The diesel buses with SCR system have lower CO and THC emis-sions but their NOx emissions are relatively high at low speeds, while the CNG-fueled buses with SCR system can ef-fectively reduce NOx emission due to higher exhaust temperature, being the most ideal choice. The particulate mat-ter mass emissions of CNG-fueled buses are far lower than diesel buses, but due to the effects of the way of dilution they emit more particles in nucleation mode.