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...

They are working on improving the busses, replacing them with hybrids and the like. Taxis too. https://www.london.gov.uk/what-we-do/environment/pollution-a...

Pedestrianisation of Oxford Street seems to be inching up the agenda. One of the big political objections is that buses are the only disabled-accessible public transport to that area but once Crossrail is operational that will no longer be true.

The buses still have to go somewhere though - the huge number of routes along Oxford Street is not about serving Oxford Street per se so much as about getting them across town. Honestly I'd be surprised if buses were the big source of pollution though - the fleet is quite modern and many of them are hybrids that deliberately run electric-only through the most polluted areas.

Electric buses then.