Drastic action is being considered to combat Britain's ever-worsening air pollution. Among government plans under review are tax incentives for cyclists, special lanes for cars carrying more than one person and compulsory roadside tests to catch vehicles emitting too many fumes. A study found almost one in three vehicles produce dangerous levels of poisonous fumes just as University of London researchers found high lead and carbon dioxide levels were affecting IQ levels in one in 10 children. Tough measures including compulsory roadside tests and fines of more than GBP2,000 (HK$25,300) are expected to be announced next month when the Government publishes a White Paper on fighting air pollution. Cheap self-service emission tests could be set up at petrol stations so drivers will have no excuse for not knowing if their car is faulty. In Leeds, city authorities aim to cut air pollution with special lanes for vehicles carrying more than one person to encourage car pooling. Transport Minister Gavin Strang has warned commuters they will have to leave their cars at home if things do not improve. Some 15 French cities will ban all traffic except electric- and LPG-powered vehicles for 24 hours in a trial set for September 22.