ou would think that battery electric cars, having no exhaust pipes, would emit less air pollution than diesel and petrol vehicles. A controversial study in 2016 said particle pollution from electric cars would be worse. Due to battery weight, electric cars are about 200-300kg heavier than comparable-size cars that burn oil-based fuel. More weight means more particle pollution from the wear of brakes, tyres and roads. This could offset the absence of an exhaust. New analysis by the University of Birmingham, suggests that regenerative braking, where the electric motor slows the car, should mean electric vehicles are less polluting in urban areas. A study in Los Angeles found that brakes on electric cars are used for about one-eighth of the time of those on oil-fuelled cars. However, the extra weight of electric cars means they are likely to emit more particle pollution on high-speed motorways. But it is not just electric cars that have a weight problem. Despite the initiative use of new materials, marketing-induced demand for more accessories and increasing SUV sales means the future petrol and diesel fleet will be heavier and produce more brake, tyre and road-wear pollution too. Our cars need to go on a diet.