Restricting the volume of high-emitting vehicles roaming city streets carries many benefits, from clearing the air to quieting the urban din and beyond. Recognition of this simple fact has led to the proliferation of clean air zones, designated regions within a city where vehicles must meet strict pollution standards or pay a fee to operate within it. At last count, over 300 such areas had been established across Europe. In London, which boasts the largest ultra-low emissions zone in the world, a study has found a secondary benefit: Kids started walking and biking to school more.

and the study in question, here: Children’s Health in London and Luton (CHILL) cohort: a 12-month natural experimental study of the effects of the Ultra Low Emission Zone on children’s travel to school