Comparative analysis of drive-cycles, speed limit violations, and emissions in two cities: Toronto and Beijing

Zhiqiang Zhai; Junshi Xu; Guohua Song; Marianne Hatzopoulou

doi:10.1016/j.scitotenv.2021.152323

Comparative analysis of drive-cycles, speed limit violations, and emissions in two cities: Toronto and Beijing

Sci Total Environ. 2022 Mar 10:811:152323. doi: 10.1016/j.scitotenv.2021.152323. Epub 2021 Dec 12.

Authors

Zhiqiang Zhai¹, Junshi Xu¹, Guohua Song², Marianne Hatzopoulou³

Affiliations

¹ Department of Civil & Mineral Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada.
² Key Laboratory of Transport Industry of Big Data Application Technologies for Comprehensive Transport, Beijing Jiaotong University, Beijing 100044, China.
³ Department of Civil & Mineral Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada. Electronic address: marianne.hatzopoulou@utoronto.ca.

PMID: 34910946
DOI: 10.1016/j.scitotenv.2021.152323

Abstract

Driving behavior and speed enforcement are both important to road safety and affect vehicle exhaust emissions. Relationships between driving characteristics and safety or emissions have been assessed in multiple studies. However, there is scant information on whether safe driving also reduces emissions and how this relationship changes across urban areas. This study makes use of two similar GPS datasets collected in the metropolitan areas of Toronto and Beijing to conduct a comparative analysis of driving characteristics, speed limit violations, and emissions. Emissions for all trips were computed using the same emission rate database derived from a Portable Emissions Monitoring System (PEMS). We observe that the average speeds in the two cities are close to 25 km/h. In Toronto, the fraction of time spent at speeds over 80 km/h on expressways is 40% higher than in Beijing. We also note a higher level of accelerations in Toronto. The trips in Beijing have approximately 14%, 57%, 14%, and 21% lower emissions of carbon dioxide (CO₂), carbon monoxide (CO), nitrogen oxides (NO_x), and particle number (PN), respectively. Drivers in Toronto violate speed limits in 93% of their trips for 21% of trip travel time while the numbers for Beijing are 43% and 4%. These differences are not necessarily due to driving behavior, but rather to driving characteristics, which encompass the effects of behavior, road network design, traffic congestion, trip patterns, and speed enforcement. A scenario was evaluated by reconstructing drive-cycles to assess the effects of speed limit enforcement for trips where violations were detected. In Toronto, if obeying the speed limit, the mean trip travel time was estimated to increase by 1.8 min. In contrast, trip emissions of CO₂, CO, NO_x, and PN were found to decrease, on average, by 5.2%, 19.1%, 5.2%, and 2.9%, respectively. Speed limit enforcement can result in lower emissions, by reducing aggressive accelerations.

Keywords: Drive-cycle; Driving behavior; Emissions; Road safety; Speed limit violation; Vehicle specific power.

MeSH terms

Air Pollutants* / analysis
Beijing
Cities
Nitrogen Oxides / analysis
Vehicle Emissions / analysis

Substances

Air Pollutants
Nitrogen Oxides
Vehicle Emissions