Traffic pollution cameras have been installed overlooking some of London's most toxically contaminated roads and junctions.
The filthy air that builds up over London regularly leads to EU safety limits being exceeded.
The devices have begun to measure the toxins emitted by each passing vehicle, to establish if they breach legal limits the cameras also have the ability to identify the vehicle's owner.
The cameras have been installed on the Marylebone Road, near Oxford Circus, and in Blackheath.
These are trials, sponsored by the Department for Transport, and overseen by scientists from King's College London.
If successful they could be used across the capital to detect badly performing cars, taxis, HGVs and buses.
The cameras shine send a laser beam through exhaust fumes, the reflected light enables scientists to determine the type and amount of pollution that is being released. A separate camera takes a photograph of the number plate.