title: Evaluating real-world CO2and NOXemissions for public transit buses using a remote wireless on-board diagnostic (OBD) approach.
abstract: The challenge to mitigate real-world emissions from vehicles calls for powerful in-use compliance supervision. The remote on-board diagnostic (OBD) approach, with wireless data communications, is one of the promising next-generation monitoring methods. We collected second-by-second profiles of carbon dioxide (CO2) and nitrogen oxides (NOX) emissions, driving conditions and engine performance for three conventional diesel and three hybrid diesel buses participating in a remote OBD pilot program in Nanjing, China. Our results showed that the average CO2emissions for conventional diesel and hybrid diesel buses were 816 ± 83 g km-1and 627 ± 54 g km-1, respectively, under a typical driving pattern. An operating mode binning analysis indicated that CO2emissions reduction by series-parallel hybrid technology was largely because of the significant benefits of the technology under the modes of low speed and low power demand. However, significantly higher CO2emissions were observed for conventional diesel buses during rush hours, higher than 1200 g km-1. The OBD data suggested no improvement in NOXemission reduction for hybrid buses compared with conventional buses; both were approximately 12 g km-1because of poor performance of the selective catalyst reduction (SCR) systems in the real world. Speed-dependent functions for real-world CO2and NOXemissions were also constructed. The CO2emissions of hybrid buses were much less sensitive to the average speed than conventional buses. If the average speed decreased from 20 km h-1to 10 km h-1, the estimated CO2emission factor for conventional buses would be increased by 34%. Such a change in speed would increase NOXemissions for conventional and hybrid buses by 38% and 56%, respectively. This paper demonstrates the useful features of the remote OBD system and can inform policy makers how to take advantage of these features in monitoring in-use vehicles.
authors.affiliation: School of Environment, State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, China.
authors.forename: Liuhanzi
authors.initials: L
authors.lastname: Yang
authors.affiliation: Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA.
authors.forename: Shaojun
authors.initials: S
authors.lastname: Zhang
authors.affiliation: School of Environment, State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, China; State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex, Beijing, 100084, China. Electronic address: ywu@tsinghua.edu.cn.
authors.forename: Ye
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Department of Environmental Studies, New York University, New York, 10003, USA.
authors.forename: Qizheng
authors.initials: Q
authors.lastname: Chen
authors.affiliation: School of Environment, State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, China.
authors.forename: Tianlin
authors.initials: T
authors.lastname: Niu
authors.affiliation: Department of Human Geography and Planning, Faculty of Geosciences, Utrecht University, P.O. Box 80115, 3584 CS, Utrecht, The Netherlands; Nanjing Tiandi Environment Research Institute, Nanjing, 210000, China.
authors.forename: Xu
authors.initials: X
authors.lastname: Huang
authors.affiliation: Nanjing Tiandi Environment Research Institute, Nanjing, 210000, China.
authors.forename: Shida
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Nanjing Intelligent Transportation System Corporation, Nanjing, 210049, China.
authors.forename: Liangjun
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Beijing Yunqingyuan Environmental Technology Incorporated, Beijing, 100084, China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: School of Environment, State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, China; State Environmental Protection Key Laboratory of Sources and Control of Air Pollution Complex, Beijing, 100084, China.
authors.forename: Jiming
authors.initials: J
authors.lastname: Hao
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D002245:Carbon Dioxide / Q000032:analysis*; D002681:China; D004784:Environmental Monitoring / Q000379:methods*; D018986:Motor Vehicles; D009589:Nitrogen Oxides / Q000032:analysis*; D058998:Remote Sensing Technology; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D009589:Nitrogen Oxides; D001335:Vehicle Emissions; D002245:Carbon Dioxide
keywords: CO(2); Diesel bus; Hybrid; NO(X); Real-world emissions; Remote on-board diagnostic