Oxford Street is packed with black cabs, they always seemed smellier to me. I used to work in Zone 4, and there'd be lines of them outside the station, with engines idling all day, next to the "Buses must switch off engines while on stand" signs.

The new taxi regulations are a welcome improvement [1], but they're weaker than they should be. Why are Euro IV cars still allowed as new taxis? Why is it only voluntary for >10 year old vehicles to be replaced? No doubt it was the best deal Kahn etc could get, but it's disappointing that London/Britain can't do better.

The buses[2] at least, are all Euro 4 standard or better, with the majority Euro 5 or better, i.e. made since 2010.

[1] https://tfl.gov.uk/modes/driving/ultra-low-emission-zone/tax...

[2] https://tfl.gov.uk/corporate/publications-and-reports/bus-fl...