For the first time in history, more than half the human population lives in cities, and the vast majority of these people are poor. In Africa and Asia, the urban population is expected to increase between 30-50% between 2000 and 2020. This shift has led to a range of new public health problems, among them road traffic safety. Road crashes are the number 1 killer among those aged 15-29, and the 8th leading cause of death worldwide. The deadly impact from accidents is aggravated by pollution from vehicles, which now contributes to six of the top 10 causes of death globally.