Real-world assessment of urban bus transport in a medium-sized city of the Middle East: Driving behavior, emission performance, and fuel consumption

In the present study, we seek to conduct a real-world assessment of the driving behavior, emission performance, and fuel consumption of urban buses in a medium-sized city in the Middle East, i.e. Isfahan, Iran. A comprehensive data collection was conducted within the main routes of the city and then the ISFahan Bus Driving Cycle (ISFBDC) was developed using a micro-trips random selection approach. On-board experiments were carried out on 20 urban buses to analyze the emission performance of the fleet in real-world conditions. The effects of bus speeds, after-treatment systems, and passenger load on emission performance and fuel consumption (FC) were also discussed. Meanwhile, the contribution of different driving modes to the CO, HC, NO_x, and CO₂ mileage(M)/fuel(F)-based(B) EFs and FC rates were investigated. Our results show that ISFBDC is unique in the world. FBEFs are strongly correlated with the speed, so much so that HC FBEFs were reduced by over 70% with increasing 30 km/h in the bus speed. Idling status contributes over 70%, 50%, 30%, and 30% to the NO_x, CO₂, and HC emission, and FC of the studied fleet, respectively. Although DPF filters in Euro IV buses could significantly reduce the NO_x emission, they have no considerable impact on the emission of the other studied pollutants. Per-passenger EFs and FCF are more than halved by 1.5 T increase in passenger loads. Euro IV buses with DPFs had better per-passenger/accumulated emission performance and fuel consumption than the others. CO₂ MBEFs of Isfahan buses are nearly twice that of Beijing buses.