Cars producing less than 100 g/km of CO2 that comply with Euro V emission regulations (which came into force on January 1st this year) will be exempt form the London congestion charge as of January 4th next year.
Owners of qualifying cars will have to register for the Greener Vehicle Discount, but the change in the rules, which was brought about through a campaign masterminded by Volvo Cars, means that many conventionally-engined models will now qualify for an exemption.
Previously, only hybrid vehicles such as the Toyota Prius and Lexus RX450h qualified, despite the fact that models like the Lexus produce well over 100g/km of CO2.
Transport for London has said that it will review the limits again in 2012, when it will decide whether to lower the threshold to 80g/km as more cars qualify.
The change in the rules has come about as a result of a campaign initiated by Volvo, which wrote to London major Boris Johnson last June pointing out that the current system was unfair for failing to recognise non-hybrid models that achieved CO2 emissions comparable to hybrids.