Drivers may face limits on the carbon they emit from their cars, which could affect the number of journeys they can make, said The Right Honourable David Miliband MP, Secretary of State for the Environment, at a free public lecture at the University of Cambridge's Faculty of Law. An option would see drivers buying and selling their carbon allowances, if the Government succeeds in persuading the EU to extend the emissions trading scheme to the roads. Motorists who emit too much carbon would have to buy pollution permits from greener drivers.Miliband's lecture The Transition Economy - a future beyond oil. was the Dr S. T. Lee Public Policy Lecture at the Faculty of Law. He was introduced by the University's Vice-Chancellor Professor Alison Richard. Aged 41, Mr Miliband is seen as one of the brightest of his generation of Labour MPs. He worked for Mr Blair's policy unit when the Labour Party was still in opposition and became head of Downing Street's policy unit after the 1997 election. The S. T. Lee lectures were established in 2003 thanks to a benefaction from Seng Tee Lee, the business executive, philanthropist and Honorary Fellow of Wolfson College, Cambridge. Each lecture considers aspects of scientific, medical or technological research and developments that are likely to have significant implications for public policy over the next decade. This was the third lecture in the series. Previous lectures have been given by Professor Sir David King, Chief Scientific Adviser to the government, and the Nobel laureate, Sir John Sulston.