[anarchop]

Diesel particulate pollution is the primary problem. London black cabs are diesel. There is a good case for banning diesel in metro and even suburban areas over time and requiring at least hybrid. Electric busses actually make more sense than cars due to the high regeneration of stopping.

[AdrianB1]

I think that banning Diesel propulsion for cabs is a great idea; first, cabs have high usage and big impact, second they are replaced faster than regular cars so the negative financial impact is minimal, they just buy electric for the next iteration and keep using electric.