Development Of Driving Cycles For Transit Buses Based-on VSP Distributions

Urban traffic has grown rapidly with the continuous expansion of urban sizes in China. As a result, vehicle emission pollutions and energy consumption resulted from the rapid increase of the vehicle population have become an important challenge being faced by many cities. Meanwhile, the transit bus has demonstrated huge advantages in terms of occupied road spaces, environmental pollution, and energy consumption because of its high passenger capacity per vehicle. Developing public transportation as a priority has been recognized worldwide as one of the best strategies to solve urban traffic problems. In order to carry out a comprehensive and objective evaluation of this strategy, it is necessary to quantify accurately emissions and fuel consumption of transit buses. To this end, developing driving cycles for transit buses is the basis to estimate fuel consumption and emissions of transit buses.In this context, this thesis uses Beijing as a case study city to analyze the relationship between operating mode parameters and emission data of transit buses based on massive data collected by using the Global Position System (GPS) and Portable Emission Measurement System (PEMS). Then, it proposes an approach for developing transit bus driving cycles based on the parameter of Vehicle Specific Power (VSP) distribution. Further, driving cycles of transit buses in Beijing are developed by using the proposed approach.First, based on a review of studies on developing transit bus driving cycles, the experiment of data collection of operating modes of transit buses is designed. The real-world driving and emission data of 15 buses are collected by using portable GPS and PEMS for three types of transit lines, express line, BRT line, and regular line.Then, after the processing of the collected experimental data, operating characteristics of transit buses for three types of bus lines and the relationship between VSP and NOx, HC, CO, and CO2 emissions are analyzed. After a comparison of the relationship between operating mode parameters and emissions, it is found that the VSP distribution can not only describe well the operating characteristics, but also explain well the emissions of buses. Therefore, a methodology for developing driving cycle by using VSP distributions as the evaluation index is proposed. Since the parameter of VSP distribution is a dimension without the meaning of the distance, the parameter of the average speed is introduced into the development of the bus driving cycles. By applying this methodology, speed-specific driving cycles for express line, BRT line, and regular line are developed based on massive operating data of buses.Finally, the developed driving cycles are evaluated two perspectives, the representativeness of operating characteristics and the accuracy of emission factor estimation. It is shown from results that the proposed driving cycle is able to reflect better the real-world operating characteristics of transit buses in comparison with the commonly used NEDC driving cycle and Four-Mode driving cycle,. In the case of the estimation accuracy of emission factors, the emission factors predicted by the proposed driving cycle are closer to the real-world emission factors.