In message , at 11:03:34
on Mon, 5 Nov 2018, David Cantrell remarked:
Probably not BUT where do you set the limit?

I don't have access to the detailed journey data needed to do a sensible
analysis.

In any case, this is
not about raking in money (even though it might do so). It's about
air quality and therefore keeping as many "polluting vehicles" out
is/should be the aim.

Wrong. The aim should be to reduce *pollution*, not to reduce polluting
vehicles. What's worse, a hundred polluting vehicles entering the zone
once a year each, or a single polluting vehicle entering every day?
Obviously the latter.

Changing it to "reducing the number of polluting *trips*" encompasses
both ideas, but still shows that its the regular commuters/deliveries
rather than people visiting Auntie Flo on her birthday who need to be
discouraged.
--
Roland Perry