London Mayor Ken Livingstone's Climate Change Action Plan, framed in April 2007, says: "More widespread carbon pricing will be essential to incentivize demand for low-carbon vehicles and fuels, and to drive innovation in further developing these technologies.' <br><br> The plans for the congestion charge to be weighted according to carbon emissions emerged in September 2006 and are expected to be introduced within the next two years. The fee for driving into central London will be variable according to the excise duty band of the vehicle. <br>