I imagine most "regulars" here can predict what my opinion is.
Stop preventing traffic from moving. By far the biggest reason
air quality in London has deteriorated so much since we've had
a Mayor is that both Mayors and TfL - with the enthusiastic
support of some anti-motor car local authorities - have done
everything they can to frustrate motorists.

The evidence of/for this is overwhelming. Oxford Street, where
car owners are banned until after 19.00 hours has the worst air
pollution, and this cannot be blamed on private motorists. TfL has
boasted repeatedly that the "congestion charge" had reduced the
number of cars in Central London, yet air pollution is far worse than
twenty years ago.

The basic logic is bone simple. A car exhaust emits fumes from the
moment the engine is switched on until the moment it is switched
off. Therefore, the longer the engine is running, the worse its affect
on air quality. If the powers-that-be change roads in such a way
that car journeys last longer, car engines will be running longer and
there will be more air pollution.

I note with utter contempt that none of the fashion-following
major candidates for Mayor has mentioned this elementary point
although they all pretend to be concerned about air quality.

Clearly some alleviation of the damage done by past and future
Mayors and TfL can be achieved by cleaner vehicles, particularly
hybrids and all-electric cars. But anyone genuinely interested in
tackling London's very serious air problem - as opposed to
to pretending to be - must start by changing the roads back to
how they were 16 years ago.