Can we afford a slow transition to cleaner buses and cleaner air?

As the top emerging environmental health risk, the air pollution is affecting everyone from head to toe, including damages on brain, neurone, respiratory, cardiovascular, reproductive system in human body. Study recently conducted by the Harvard TM Chan School of Public Health even showed human exposure to higher air pollution would lead to higher COVID-19 death rate.

Air pollution is Hong Kong’s biggest cause of social and environmental injustice. It harms not only citizens today but, because of its trans-generational effects on the unborn and youngest members of the community, it will project its ill health effects well into the later years of this century.[1]

Therefore, it is a race between the progress to clean up the air and the devastating impact the air pollution made to the society. It is obvious any delays in cleaning up the air will cause large-scale impairment to health related quality of life, including illness days, hospital admissions and time off school and work. For instances, in 2019 one year alone, Hong Kong has suffered additional 1,745 premature deaths, 130,000 hospital bed days, 2.3 million doctor visits, and HK$20.8 billion economic loss due to air pollution[2].

For the last two decades, most Hong Kong population has exposed to a dangerously toxic level. In terms of Nitrogen Dioxide (NO2), The Nitrogen Dioxide (NO2) in Hong Kong doubled that of World Health Organization’s (WHO) recommended safe level from 1998 to 2018 (actual annual average concentration of roadside NO2 was at least 80 microgram per cubic meter, doubling the WHO’s standard at 40).

Figure 1:  Long Term Trend of Major Air Pollutants in Hong Kong

It is indisputable that the air pollutants emitted from vehicular traffic are associated with additional risk for dying from cancers and developing respiratory and circulatory diseases.

Regional study[3] showed that Heavy Duty Diesel Vehicles (such as the franchised buses and freight vehicles) and Light Duty Gasoline Vehicles (such as the LPG public light buses and taxis) account for over 40% of respiratory mortality and lung cancer among population in Hong Kong due to nitrogen oxides (NOx) emission.

Currently, commercial vehicles in Hong Kong account for 95% of the vehicular emissions of respiratory suspended particles (RSP) and nitrogen oxides (NOx), both major air pollutants.

One of the key emitters are the franchised buses. According to recent official update[4], franchised buses account for nearly one fifth of key pollutants emission in Hong Kong including the Respirable Suspended Particulates (19%), Fine Suspended Particulates (19%), and Nitrogen Oxides (18%).

Given the strong public health concern, the process of transforming to Lower or Zero Emission buses is slow and disappointing. By end of 2019[5], Electric Buses, Euro VI Diesel Buses and Hybrid Buses account for only 7% of the total bus fleet in Hong Kong (among the 6,177 strong bus fleet in Hong Kong, there are only 31 Electric Buses and 400 Euro VI (including Hybrid) Buses operating in service).

Engine class KMB* Citybus (F1)* Citybus (F2)* NWFB* LW* New Lantao Bus* Total Proportion to all buses
No. of Euro II Diesel Bus 22 0 0 0 0 0 22 0%
No. of Euro III Diesel Bus 891 0 0 7 18 13 929 15%
No. of Euro IV Diesel Bus 93 24 0 38 32 23 210 3%
No. of Euro V Diesel Bus 2823 675 221 528 225 113 4585 74%
No. of Euro VI Diesel Bus (incl. Hybrid) 220 47 20 108 0 5 400 6%
No. of Electric Bus 16 5 0 4 4 2 31 1%
No. of all buses 4,065 751 241 685 279 156 6,177 100%
Proportion of Euro VI Diesel Bus (incl. Hybrid) to all buses 5.4% 6.3% 8.3% 15.8% 0.0% 3.2% 6.5%
Proportion of Electric Bus to all buses 0.4% 0.7% 0.0% 0.6% 1.4% 1.3% 0.5%

Table 1:  The numbers of licensed buses owned by each franchised bus company by end of 2019


  • KMB – The Kowloon Motor Bus Company (1933) Limited
  • Citybus (F1) – Citybus Limited (Franchise for Hong Kong Island and Cross-Harbour Bus Network)
  • Citybus (F2) – Citybus Limited (Franchise for the Airport and North Lantau Bus Network)
  • NWFB – New World First Bus Services Limited
  • LW – Long Win Bus Company
  • New Lantao Bus – New Lantao Bus Company (1973) Limited

According to data publicized by the Transport and Housing Bureau[6], we compile a table which shows the timeline for Hong Kong’s franchised bus fleet to be retired. The franchised bus operators have committed to retire buses from their fleets before the anniversary of the 18th year from first registration.

At current scenario, we will have to wait for another 16 years to before the last batch of Euro V Diesel Buses to be retired by 2036.  The EV Roadmap, one that we anticipate to cover franchised buses, should provide an alternative timeline in order to accelerate the clean up of franchised bus related air pollution and public health consequences.

Engine 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 Total
Euro II 318 150 468
Euro III 183 400 191 175 47 106 53 20 1175
Euro IV 4 23 72 43 11 153
Euro V 144 288 250 441 401 821 746 676 38 3805
Euro VI 6 6 12
Electric 8 5 11 24

Table 2:  The numbers of licensed franchised buses to be retired


[1] Air Pollution and Public Health – The current avoidable burden of health problems, community costs and harm to future generations. Professor Anthony J Hedley. Department of Community Medicine, School of Public Health, The University of Hong Kong. LC Paper No. CB(1) 733/08-09(02).

[2] Hedley Environmental Index. The School of Public Health of The University of Hong Kong.

[3] Xingcheng Lu, Teng Yao, Ying Li, Jimmy C.H. Fung, Alexis K.H. Lau, Source apportionment and health effect of NOx over the Pearl River Delta region in southern China, Environmental Pollution, Volume 212, 2016, Pages 135-146, ISSN 0269-7491, (2016)

[4] Examination of Estimates of Expenditure 2020-21, HKSAR Government (2020). Reply Serial No. ENB041.

[5] Ibid.

[6] Examination of Estimates of Expenditure 2018-19, HKSAR Government (2018). Reply Serial No. THB(T)364.

June 05 2020 | PF

Clean Air Network (CAN) conducted a study for 2 weeks in March 2020, with the purpose to identify the level of air pollution concentration (Nitrogen Dioxide, NO2) at 10 bus stops

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