Braking is good for the air - really?

If you drive 20 km/h slower, fewer pollutants are emitted: This applies to the reduction from 130 to 110 km/h and from 90 to 70 km/h, for example. At 30km/h, on the other hand, the studies are not unambiguous and the effects have to be seen in context: Since it is safer for road users, several people dare to ride a bicycle. In this case, speed-30 zones/roads are good complementary measures to environmental zones!