In a reply to a mayoral question from Stephen Knight AM, Liberal Democrat London Assembly environment spokesperson, the response stated that "officials are considering how best to do this for the following edition of the LAEI [London Atmospheric Emissions Inventory], which is likely to be published in 2017".
Auxiliary engines are generally diesel powered and are currently unregulated. Despite its small size, the engine used to power refrigeration on trucks can emit up to 29 times more potentially carcinogenic particulate matter than a modern Euro 6 diesel truck engine.
Discussing the development, Stephen Knight AM says: "Auxiliary engines on delivery vehicles clearly have a serious impact on London's air quality and it is time the mayor took firm action to bring these dangerous emissions under control. These transport refrigeration units are a 'hidden polluter' and their emissions must now be properly measured and controlled."
Dr Tim Fox, international ambassador for Dearman – which is currently trialling a zero-emission refrigeration system – says the response shows a "small but significant shift" in attitude.
"We could make a sizeable impact on both NOx and PM pollution and improve the quality of the air we breathe, by bringing transport refrigeration units up to modern emissions standards – or even better making them zero emission," adds Fox.
"That small change could have a very big impact."