A real world problem not in the reports:

Pollutants from vehicles using new road tunnels to be built under Sydney Harbour will be up to 26 per cent higher than the government's baseline modelling for the multibillion-dollar project unless tougher European emissions standards are introduced.

https://www.smh.com.au/national/nsw/pollutants-from-new-sydney-tunnel-to-soar-without-stricter-standards-20200306-p547ln.html