If you walk a kilometre to work in a city along a road used by commuters, you could quite easily pass 200 cars queuing and moving slowly along.
Car engines produce exhaust emissions that contain nitrogen dioxide, carbon monoxide and particulate matter.
Particulate matter, or black carbon, is associated with cardiovascular diseases and respiratory problems, such as asthma.
Air quality is becoming an important issue in many parts of the world.
The court considered the threat to public health “exceptional circumstances”, with nitrogen dioxide pollution is linked to 23,500 deaths a year in the UK.
The draft plan focuses on introducing more efficient vehicle technology and moving to electric vehicles as key steps to reduce air pollution.
Diesel vehicles are the biggest contributor to the problem, with nitrogen dioxide emissions from them at nearly 10 times the emissions limits set out in Euro standards.
If you walk or cycle along a busy route, you could be exposed to 40% more black carbon than along a quiet route.
This is hard to measure, however, as some measurements have not found a statistically significant difference between peak and off-peak hours.
The study still found that you could reduce expose to particles by walking a less polluted route.
You could also do this by avoiding peak hours when there are lots of commuters heading to work.
The issue is important enough for Defra to have a daily pollution forecast. Parents and schools are also running campaigns to get drivers to stop idling when stationery.
A final air quality plan is expected to be released by the end of the month.
Change is going take time, however, with the provisions being phased in by 2050.
If you have the ability to work flexibly, perhaps now is the time to start thinking about avoiding peak times when making your way to work.