I don't trust that document one bit!!!
If you look on google for Nitrogen Dioxide maps of London...
https://www.google.co.uk/search?q=Nitrogen+dioxide+map+london&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjb0d-z2aDZAhWysKQKHS77AIAQ_AUICigB&biw=1301&bih=620#imgrc=XitTf4Sx6eBhBM:&spf=1518449559659You can make a few observations...
1. They usually don't show the M25, which is probably one of the biggest contributors... Yet because the mayor can't tax it and make revenue out of that, it's conveniently not mentioned?! (...and I should think one of the worst places would have been Dartford crossing before the gates were automated. They used to cause congestion and stop the traffic with no regard for the environment so they could make money!!)
2. The Nitrogen Dioxide maps usually show a big blob over central London and an almost equal size blob over Heathrow... Yet when you look at the data on that web link there is no mention of the contribution of planes. It's designed to make everyone think cars are the bad guys.
Typical manipulated ecomentalist bullsh*t!!
If you ever meet an ecomentalist, ask them why it is you have a 'Carbon' footprint and not a 'Hydrogen' footprint, because surely I'm producing twice as much hydrogen?!
You may have gathered I'm not very happy about this.