Roadside air pollution is one of the biggest threats to public health in Hong Kong. It affects living quality and raises various social costs, damages the city’s competitiveness, image and business environment.

Roadside air pollution affects us all. In fact, over the last 20 years, Hong Kong’s roadside air quality has never reached the World Health Organization’s recommended level, and at present stays up to twice as high as the safe standard. What happened?

The key factors affecting level of roadside pollution include vehicular emission control, traffic congestion, and the city planning.

Vehicular Emission Control 

Old (Euro III or below) diesel commercial vehicles, including goods vehicles, non-franchised buses, public light buses, emit relatively large amount of air pollutants.

Even LPG/petrol taxi and public light bus, without proper maintenance, would emit large amount of air pollutants especially nitrogen dioxide.

There are franchised buses, non-franchised buses, private cars, motorcycles which all contribute to different level of pollution.

Over the last few years, the government has implemented different measures to control emission from road transport, including the phase out of old (pre-euro IV) diesel commercial vehicles progressively by end of 2019, retrofitting franchised buses to reduce emission, and subsidizing LPG/petrol taxi and public light buses to renew catalytic converters.

However, even with the completion of all these direct emission control measures (or “end-of-pipe” measures), Hong Kong roadside air quality would not be able to meet our 2020’s target. The reason is that, the improvement made by “end-of-pipes” measures will be offset by the uncontrolled growth of vehicle fleet.

Similarly, there has been on-going discussion and exploration of cleaner fuel. However, before we are able to achieve full usage of zero emission vehicles on the road, we should not neglect the great importance of traffic congestion in worsening roadside air pollution.

Traffic Congestion 

Multiple factors lead to the worsened traffic congestion in Hong Kong. As identified by the Transport Advisory Committee in its 2014 report, the key factor is the excessive number of vehicles on the roads.

The vehicle growth has gone uncontrolled. Between 2006 and 2016, the number of licensed vehicles in Hong Kong increased by 35 per cent, compared with the growth rate of 16 per cent between 1996 and 2006. By the end of last year, the city had some 746,000 licensed vehicles. If the trend persists, Hong Kong will see a million vehicles by 2026.

Traffic congestion not only prolongs commuting time, but also commuters’ and pedestrians’ exposure to roadside air pollution.

Based on our analysis of the patterns of transport activities and air pollution, based on 2016 data, we arrived at two findings. First, traffic peak hours aligned with the pollution peak hours. The associated health risk escalated by as much as 2.6 times during peak hours, compared with quieter periods.

Second, areas with higher traffic volume also recorded higher air pollution. Districts in New Territories West (Tuen Mun, Tsuen Wan and Kwai Chung) and Kowloon West (Sham Shui Po) recorded higher traffic volumes and higher levels of pollution, compared to east part of Hong Kong.

City Planning

The vehicle-dominated culture is deep-rooted in our city.

Our city is built in a way to facilitate the use of vehicles and marginalize the existence of alternative greener modes of transport, including bicycle and pedestrianization.

The consequences are the relentless growth of vehicles number and usage in Hong Kong.

Moreover, in certain areas, the roadside air pollution is worsened by the Street Canyon effect, where high rise buildings on the sides of traffic road are trapped the air pollutants.


A multi-pronged approach should be taken to tackle roadside emission, which involve collaborative effort from different sectors.

Vehicular Emission Control :
Low Emission Zone

In 2011, the Government set up pilot low emission zones (LEZs) in Causeway Bay, Central and Mong Kok and encouraged franchised bus companies to deploy buses meeting Euro IV or higher emission standards (low emission buses) to ply those routes passing the pilot LEZs.

One of the main purposes of setting up low emission zones, is to reduce roadside air pollution and safeguard public health. However, there are various problems of the low emission zones discovered:

  • According to the documents submitted by Environmental Protection Department, the pilot scheme only covered franchised buses and the pilot areas consisted of three streets in Causeway Bay, Mong Kok and Central. They are technically “low emission streets” instead of zones.
  • The pilot scheme regulated franchised bus only. However, according to 2014 Environmental Protection Department’s data, franchised bus takes up 40% of the traffic flow, which means, there are other types of vehicle on the road. The environmental benefits achieved by setting up the low emission zone might be offset by pollution emitted by non-franchised buses.

Therefore, CAN suggested to include other types of vehicle

  • The delay of deploying all environmental friendly buses in the low emission zones, from 2015 to 2016.

CAN believes that, setting up a genuine low emission zone (one that covers more geographic space especially areas with high density of pedestrian, and regulates various types of vehicle) requires the joint effort of the Environment Bureau and the Transport and Housing Bureau.

To improve roadside air pollution, the government and the public should not depend only on the implementation of “end-of-pipe” solutions (reducing direct emission from road transport). Importantly, holistic and sustainable transport policies, including setting up of low emission zone, should be considered.

combustion fumes coming out of car exhaust pipe

◎ Combustion fumes coming out of car exhaust pipe

Traffic Congestion :
Electronic Road Pricing Pilot Scheme

In December 2015, the Transport and Housing Bureau launched the Public engagement for Electronic Road Pricing Pilot Scheme in Central and its Adjacent Areas.

Since the 80s, there were discussions about electronic road pricing. Over the past two decades, many foreign cities have adopted the electronic road pricing. Their experiences provided valuable insights to our discussions in Hong Kong.

Clean Air Network (CAN) generally agrees that Electronic Road Pricing (ERP) can reduce traffic congestion and related air pollution issues, but the government should provide other necessary complementary measures like setting up pedestrian and tram only precinct in Des Voeux Road Central, and support with transport management policies. ERP should incorporate polluter-pays principle in its charging approach in order to let the road users share their social costs caused by traffic congestion.

City Planning :
Transforming Des Voeux Road Central to a pedestrian and tram only precinct

The Des Voeux Road Central Initiative is a non-profit initiative to create a pedestrianized green artery along Des Voeux Road Central, from Western Market to Pedder Street.

The DVRC Initiative aims to improve the experience of Hong Kong’s Central Business District by reconsidering traffic management and by creating a pedestrian and tram precinct along Des Voeux Road Central. The community, government, professionals, academics, business operators, property owners and all other stakeholders are invited to join the DVRC Initiative as supporters, sponsors, collaborators and friends.

Smart Move

“Smart Move” is an open platform to encourages participants to adopt low emission transport modes, and experience a new lifestyle. It is also a movement which aims to inspire and initiate mentality and behaviour changes. Eventually, such societal changes may lead to the formation of sustainable transport management policy, which reduces roadside air pollution.

Traffic management policy

Clean Air Network suggests the government to focus on planning and traffic management policy tools to curb car growth and the public demand to vehicles. At the same time, the government should responsibility to adopt compact city planning in which walk-ability and cycling should be highlighted.

Story posted on
10th Jan, 2017


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