The poisonous gases emitted by a vehicle include CO (Carbon monoxide) which is a colourless, odourless killer of anything that breathes if present in high enough concentrations. SO2 (Sulphur Dioxide) manifests as acid rain amongst other things.

The Lead and/or Benzine added to Petrol combine with other elements to make up many other poisons when burned. Even the smoke or smog that hangs over our cities as a result of heavy traffic on congested roads is unpleasant, without considering just what it contains, what harm it can do if breathed.