Cars are well known for their tail pipe pollution. Great efforts have been made to reduce such. But there are other sources associated with vehicles that are not normally considered. Vehicle exhausts are responsible for only a third of traffic pollution, according to new research. The study, published in Atmospheric Environment, says nearly half of air pollution from road traffic is due to non-exhaust sources such as brake wear, road surface wear, and particles whipped up from the road by passing vehicles. Professor Ranjeet Sokhi, of the University of Hertfordshire, who led the study, is calling for greater control of non-exhaust pollution.