Drive-by emissions test could monitor London LEZ

Date: 23 July 2007

New drive-by emissions-testing technology already used in 20 American states could form part of the London low-emissions zone system as well as providing larger fleets with a way of monitoring their output.

Enviro Technology Services has already carried out pilot schemes in Manchester and Bristol. Transport for London follows suit this autumn with a two-week pilot scheme aimed at getting some "in-situ data" ahead of the LEZ being introduced early next year.

The roadside equipment doesn't test for CO2, focussing on particulates and NOx emissions that contribute to local air quality problems. The system works by using ultraviolet and infrared light to measure the concentration of different gases in tailpipe emissions. It can't tell how much load the engine was under as it drove past, though it will only take a measurement if it recognises that a car was accelerating through the sensor.

Company bosses claim the worst 20% of vehicles can emit up to half of all car-based pollution.

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