Families from Sheffield took part in a test to see who breathes in more pollution on the school run - kids who walk, bike or go by car.

The experiment saw three families take air quality monitors with them to school to measure levels of PM2.5, small particles of air pollution that are about 30 times thinner than a human hair.

Each method of transport was found to be over the World Health Organisation recommended safe limit, but which was the worst?

Click here to see the results.