Here's a brief response to Simon's points.
" ... too many taxis are a symptom that the mass transit (i.e. public
transport minus taxis) system isn't working properly."
I agree that their current use (rather than their number)contributes
to the problem.
" ... but not if it means more people choosing to use them in
preference to mass transit."
Shared taxis and mass transit are complimentary rather than
exclusionary in relationship. Anzir Boodoo said that "Integration
has to be the key". An analogy is: shared taxis (xTransit modes) are
to capillaries as mass transit modes are to veins and arteries. Both
are vital to movement. Not everyone in high density cities can or
wants to wait for or walk to the bus/mass transit connection, so most
conveniently get into their cars for the entire journey. Shared
taxis (xTransit) can make that connection and replace the majority of
trips done by car.
Some of the many factors that determine this choice are:
_ fares for bus transit are less expensive than shared taxis
_ mass transit has mobility restrictions that shared taxis don't
_ mass transit has to keep to schedules that shared taxis don't
xTransit replaces the car where conjestion charging restricts their
use. Which changes current behavior more efficiently remains an