Air Pollution

Asia's megacities are using sensors to detect high-polluting vehicles

Smog across a cityscape

Driving change ... remote sensors can identify the owners of high-polluting cars. Image: Unsplash/Photoholgic

Andrea Willige
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Air Pollution

This article is part of: Centre for Urban Transformation

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  • Air pollution in the world’s biggest cities is linked to premature death, a new study demonstrates, with Asia particularly affected by high levels of air pollution.
  • Cars are the dominant source of noxious emissions affecting the health of city-dwellers.
  • Hong Kong SAR has made substantial reductions in roadside air pollution by introducing remote sensing technology to identify the highest-emitting vehicles.

A new study from University College London has linked fine particulate emissions to premature deaths across some of the world’s fastest-growing cities. Air quality in Asia is particularly affected by high levels of air pollution, with New Delhi, India and Dhaka, Bangladesh recording fine particle emissions at more than 10 times the guideline levels set by the World Health Organization.

These high emissions contribute to excess deaths in cities across Asia and Africa, as the chart below highlights.

A diagram showing the increase in premature deaths from 2005 to 2018
Cities in tropical regions are affected by high levels of air pollution. Image: ScienceAdvances

Fine particles are only a small fraction of the pollutants that affect air quality - and ultimately our environment and health. While the causes are many - including sandstorms, sea fog and burning biomass - cars are the main contributor to air pollution in cities and the source of many of the most dangerous pollutants.

City air pollution: catching the worst offenders

Some Asian megacities are taking a tough stance on the worst offenders. Hong Kong SAR - which ranks in the midfield for air pollution globally - has improved air quality by using remotely operated roadside sensors to identify vehicles emitting high levels of pollutants - and requiring the owners of those vehicles to fix them.

Unlike low-emission schemes elsewhere in the world, where the deciding factor for road fees and fines is the vehicle model’s official emission record, Hong Kong’s sensors are measuring the actual exhaust fumes emitted in traffic. This is because as vehicles get older, their emission performance typically worsens, especially if they are not maintained regularly.

Sensors installed on highway ramps use infrared and ultraviolet light to detect air pollutants such as carbon monoxide, nitrogen oxide and hydrocarbons from the exhausts of passing vehicles. A camera records the number plate so that the owners of the most polluting vehicles can be notified. Rather than receiving a fine or charge, they must instead repair their vehicles and pass a subsequent emissions test, both at their own expense. Only then are they allowed back on the road.

Charts showing the effectiveness of the Hong Kong RS high-emitter enforcement program.
Thousands of heavily polluting vehicles have been detected by sensors in Hong Kong SAR. Image: ScienceAdvances

A study by the University of Technology Sydney has demonstrated the success of the scheme in terms of reducing air pollution. Between its introduction in 2014 and 2018, more than 16,000 vehicles were caught. 96% of these were subsequently repaired and passed the required emission test. The remainder either did not take the test or failed it, resulting in their licences being cancelled. The number of high emitters among taxis were significantly higher than among private cars.

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Improved air quality as a direct result

A comparison between 2012 and 2015 - a year after the introduction of the scheme - showed a drop of more than a quarter in roadside emissions of both carbon monoxide (CO) and nitrogen oxides (NOx). At the same time, ambient air quality saw reductions of between 8 and 10%. Overall, emissions from road transport were down by a third and half for CO and NOx respectively compared to the previous three years.

The Hong Kong SAR scheme could serve as a model for other megacities as they continue to grow, and for cities of any size across the world looking to reduce air pollution from road transport.

The World Economic Forum is addressing the issue as part of its Alliance for Clean Air, which unites a wide range of private sector leaders in initiatives to reduce air pollution.

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The views expressed in this article are those of the author alone and not the World Economic Forum.

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Air PollutionCities and Urbanization
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