trax trains

Train-mounted emissions detector allows local air pollution monitoring on the cheap


Mobile sensors than can detect greenhouse gas emissions have been fitted to trains in order to monitor air quality at a lower cost.

Research-grade air quality sensors typically cost around $40,000 (approximately £30,400) each, according to researchers at the University of Utah. To lower this expense, they trialled attaching mobile sensors to light rail trains which form part of the public transport network in the Salt Lake Valley area.

They said that about 30 stationary sensors would be needed to cover the same area that the train sensors are capable of covering.

“Pollutant levels in the atmosphere are going to be rapidly changing in the coming decade as clean energy technologies are deployed,” said Logan Mitchell, co-author of the study.

“Cost-effective atmospheric monitoring will help policymakers understand what policies lead to reductions in pollutant levels, where there needs to be more focus and if there are environmental inequalities emerging as some areas reduce their emissions faster than other areas.”

The team first tested the system by placing air inlet tubes out the window of an unoccupied driver’s cab.

“I noticed that there was a small CO2 bump every time the 'TRAX' train (pictured) stopped at a train station,” Mitchell said. “This confused me initially, but I realised that the inlet tubes sticking out of the driver window were actually picking up human respiration from people standing at the train platform waiting to board the train!”

The project continued by placing the sensors on the roof of the train so they aren’t affected by people waiting on the train platforms.

Nasa satellites can also be used to make emission estimates for cities around the world, a technique the team is pursuing in tandem.

“These satellite measurements are useful for assessing whole cities and for cities that lack ground observations,” said co-author John Lin, “but the TRAX-based sensors allow for more granularity in emissions throughout the city and can complement the space-based observations.”

As cities work to reduce environmental inequalities, mobile air monitoring can also help determine if some urban areas’ air is improving faster than others, the researchers said.

They added that the cost savings achieved by their approach are “staggering” as not only are fewer sensors needed, but they also need less manpower than that which would be required to maintain a network of 30 ground-mounted sensors.

Air pollution levels around the world have fallen in 2020 due to the coronavirus pandemic curtailing travel and industry activities. A study in April found that in Europe, 11,000 premature deaths from air pollution may have been avoided due to the fall. 

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