Improvements from cleaner engines are being more than offset by the growth in vehicle ownership.

With some young driver policies costing more than £2,000 a year, vehicle ownership doesn't make financial sense.

The rules allow governments to be given automatic access to vehicle ownership records held by other countries.

It argues that further private vehicle ownership requires road building that will constrain the space needed to improve other infrastructure.

Global vehicle ownership per capita in 2010 was 148 vehicles in operation per 1000 people.