Evaluating real-world CO2 and NOX emissions for public transit buses using a remote wireless on-board diagnostic (OBD) approach

Liuhanzi Yang; Shaojun Zhang; Ye Wu; Qizheng Chen; Tianlin Niu; Xu Huang; Shida Zhang; Liangjun Zhang; Yu Zhou; Jiming Hao

doi:10.1016/j.envpol.2016.07.025

Evaluating real-world CO₂ and NO_X emissions for public transit buses using a remote wireless on-board diagnostic (OBD) approach

Environ Pollut. 2016 Nov:218:453-462. doi: 10.1016/j.envpol.2016.07.025. Epub 2016 Jul 18.

Authors

Liuhanzi Yang¹, Shaojun Zhang², Ye Wu³, Qizheng Chen⁴, Tianlin Niu¹, Xu Huang⁵, Shida Zhang⁶, Liangjun Zhang⁷, Yu Zhou⁸, Jiming Hao⁹

Affiliations

¹ School of Environment, State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, China.
² Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI, 48109, USA.
³ 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.
⁴ Department of Environmental Studies, New York University, New York, 10003, USA.
⁵ 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.
⁶ Nanjing Tiandi Environment Research Institute, Nanjing, 210000, China.
⁷ Nanjing Intelligent Transportation System Corporation, Nanjing, 210049, China.
⁸ Beijing Yunqingyuan Environmental Technology Incorporated, Beijing, 100084, China.
⁹ 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.

PMID: 27443949
DOI: 10.1016/j.envpol.2016.07.025

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 (NO_X) 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 CO₂ emissions for conventional diesel and hybrid diesel buses were 816 ± 83 g km^-1 and 627 ± 54 g km^-1, respectively, under a typical driving pattern. An operating mode binning analysis indicated that CO₂ emissions 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 CO₂ emissions were observed for conventional diesel buses during rush hours, higher than 1200 g km^-1. The OBD data suggested no improvement in NO_X emission reduction for hybrid buses compared with conventional buses; both were approximately 12 g km^-1 because of poor performance of the selective catalyst reduction (SCR) systems in the real world. Speed-dependent functions for real-world CO₂ and NO_X emissions were also constructed. The CO₂ emissions of hybrid buses were much less sensitive to the average speed than conventional buses. If the average speed decreased from 20 km h^-1 to 10 km h^-1, the estimated CO₂ emission factor for conventional buses would be increased by 34%. Such a change in speed would increase NO_X emissions 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.

Keywords: CO(2); Diesel bus; Hybrid; NO(X); Real-world emissions; Remote on-board diagnostic.

MeSH terms

Air Pollutants / analysis*
Carbon Dioxide / analysis*
China
Environmental Monitoring / methods*
Motor Vehicles
Nitrogen Oxides / analysis*
Remote Sensing Technology*
Vehicle Emissions / analysis*

Substances

Air Pollutants
Nitrogen Oxides
Vehicle Emissions
Carbon Dioxide