How. do roads aff affect air quality?

Question: How. do roads aff affect air quality?
- Keywords:
  air quality,
  pollution,
  road
Asked by anon-200236 to Hannah on 14 Mar 2019.
- Hannah answered on 14 Mar 2019:
  
  Emissions from vehicle exhausts are a significant source of air pollution, including nitrogen oxides, carbon monoxide and particulate matter, therefore air quality by roads tends to be poorer than in other locations.

Question: How. do roads aff affect air quality?