Roadside Sensor Networks Prove Their Worth in Tracking — and Fixing — High-Polluting Vehicles

Researchers from the University of Technology Sydney (UTS), working with the Hong Kong Environmental Protection Department (HKEPD) and the Hong Kong Vocational Training Council, have published a study suggesting that remote sensor networks installed by the side of roads can have a measurable impact on air pollution from high-emitting vehicles.

"Car exhaust fumes contain poisonous gasses such as carbon monoxide, nitrogen oxides, and particulate matter that cause lung cancer, heart failure, asthma and other diseases," explains John Zhou, professor at UTS and co-author of the study into the efficacy of monitoring equipment designed to pinpoint the most polluting vehicles — and to ensure their owners get the issue rectified.

"Remote sensing equipment uses a sensor and light beam to measure chemical concentrations in the exhaust as a vehicle drives past," Zhou says of the system under investigation, a deployment of sensors at over 150 monitoring sites. "A camera records the license plate, so vehicles can be identified for inspection and repair."

Between 2014 and 2018, the study found that the sensor network successfully identified 16,365 vehicles with high exhaust emissions — an impressive 96.3 percent of which were, once the owner had been notified, repaired and succeeded in passing the Hong Kong Transient Emission Test (HKTET). Just 1.4 percent of vehicles failed, and had their license cancelled; 2.3 percent of vehicles were not submitted for testing, and were likewise de-licensed.

"This is the first study of its kind to link on-site measurement of vehicle emissions with follow-up actions for repair of the high polluting vehicles. It provides insights for policymakers not just on monitoring but also implementing enforcement programs," says Yuhan Huang, first author of the study.

"Targeting the small portion of high emitters for vehicle emission control significantly reduces the repair cost and time for both the government and vehicle owners, compared to passive sampling or periodic inspection."

Using data from the study, combined with data from air quality monitoring systems and chassis dynamometer testing, the researchers conclude that repairing all high-emitting vehicles to bring them in line with standards would reduce total hydrocarbon pollution by 22 percent, carbon monoxide pollution by 47 percent, and nitric oxide pollution by 39 percent.

The team's work has been published under open-access terms in the journal Science Advances.