Emission factors (EFs) are empirical functions that envisage the amount of an emitted pollutant based on travel activity and vehicle characteristics. This paper aims to estimate on-road gaseous emission factors of gasoline passenger vehicles under urban Malaysian road traffic conditions. Eleven vehicles were tested and the carbon monoxide (CO), carbon dioxide (CO₂) and nitrogen oxides (NO_x) emission results were analyzed according to driving conditions. The effects of inter-vehicle variability in terms of accumulated mileage on emission factors were explored using regression analysis. The links of real driving condition on exhaust emissions were examined using hierarchical cluster analysis. The emission factors of CO, CO₂ and NO_x were calculated using a fuel-based approach. The 95% confidence intervals obtained for the population mean of emission factors were CO: 0.76 $\pm$ 0.15 g/km, CO₂: 236.02 $\pm$ 14.98 g/km, NO_x: 0.23 $\pm$ 0.03 g/km. Vehicle age as echoed by accumulated mileage was responsible for the increase in the average emission factors of CO and NO_x. The results of the cluster analysis formed four meaningful clusters which described driving conditions and exhaust emissions. Higher observations were recorded for Cluster 1 (43.25%) indicating low vehicle speed and better fuel efficiency produced low NO_x and CO emissions but high CO₂ emissions. The measurements reported in this paper highlight the significance of this work in quantifying CO, CO₂ and NO_x emissions from gasoline passenger vehicles under real-world driving conditions of urban street in Malaysia where there is a paucity of EFs studies.

排放因子（EFs）是经验函数，可根据行驶活动和车辆特性设想排放的污染物量。本文旨在估算马来西亚城市道路交通条件下汽油乘用车的道路气体排放因子。测试了11辆汽车，并根据驾驶条件分析了一氧化碳（CO），二氧化碳（CO ₂）和氮氧化物（NO _x）的排放结果。使用回归分析探讨了累计里程方面的车辆间可变性对排放因子的影响。使用分层聚类分析检查了实际驾驶条件对废气排放的影响。CO，CO ₂和NO _x的排放因子使用基于燃料的方法进行计算。排放因子总体平均值的95％置信区间为CO：0.76$\pm$0.15 g / km，CO ₂：236.02$\pm$14.98克/公里，NO _X：0.23$\pm$0.03克/公里 如附和积聚里程车辆年龄为负责在CO和NO的平均排放因子的增加_X。聚类分析的结果形成了四个有意义的聚类，它们描述了驾驶条件和废气排放。更高观察结果记录为第1组（43.25％），表明较低的车辆速度和更好的燃料效率产生的低NO _X和CO排放，但高的CO ₂排放量。在本文报道的测量，强调这项工作的意义在量化CO，CO ₂和NO _X在马来西亚城市街头的真实世界的驾驶条件，其中有EF文件研究的缺乏下汽油乘用车的排放量。