Transport for London’s proposed changes to the London Congestion charge, in which cars of 120g/km CO2 and below could be exempted from payment, may actually increase the output of CO2 in the city, says Clean Green Cars.

Evidence for this comes from an independent report (by AEA) commissioned by TfL itself, which suggests that ‘there could be an increase in the overall numbers of cars travelling within the zone,’ and that the consequent ‘increased congestion would mean all vehicles moving more slowly and hence increased CO2 emissions.’

Setting the threshold at 110g/km will diminish the risk, identified in the AEA report, of Londoners switching to 120g/km-and-below models in sufficient numbers to cause congestion to increase, making the changes self-defeating, as will the imposition of a US$8 charge rather than the exemption currently proposed. The Congestion Charge is still intended to be a charge on congestion, Mayor Ken Livingstone has stressed, and it therefore makes sense to charge any vehicle that enters the zone.

The 110g/km limit would also encourage car manufacturers to work harder to develop cars with even lower emission. There are already several dozen models on sale emitting 120g/km CO2 or less, and more are arriving by the month because this is not a difficult target to reach. Far fewer 110g/km-and-below models are already on sale in the UK, including the Volkswagen Polo BlueMotion, the SEAT Ibiza ecomotive and the new Mini diesel as well as the Toyota Prius and Honda Civic hybrids.

The $24 charge for vehicles over 225g/km, reduced from the proposed $50, is designed to discourage potentially well-off owners of these vehicles buying an additional low-emission car instead of replacing their high-emission model.