In multiple European cities now I see taxis being allowed to use the bus lane (while of course regular cars are not).

What's the policy justification for this?

1) Taxis carry more people than typical cars do on a daily basis.

2) And have more “uptime” as they aren’t taking up parking spaces.

3) They’re also more likely to be doing short hops, where a little extra speed from the bus lane is nonlinear. Saving 5 mins on 10 min ride is much bigger benefit than saving 5 mins on 60 min trip.

4) All that encourages people to leave cars at home and use Uber/taxis in the city.

5) All that gets better with self-driving.

6) Basically, you’d prefer a city with self-driving 24/7 ride-share taxis to one with conventional cars. It will have less traffic and better utilization. (Of course if all cars switch over then bus lanes will again get crowded.)