Yes, cruising around looking for customers is EXACTLY what you're counting when you include a "return trip" extra for a taxi. If they find another customer righ

Yes, cruising around looking for customers is EXACTLY what you're counting when you include a "return trip" extra for a taxi. If they find another customer right after dropping off the prior then there are zero wasted miles. Taxis use up more road spacetime the more time they spend looking for a customer, while private cars use up more road spacetime the more time they spend parked or looking for parking. Realistically, in dense places, private cars spend a lot of time looking for parking, and almost all of their lives parked, but cabs are occupied more often than not. On the other hand in sufficiently undense places, a cab would have to spend a lot of time looking for passengers while private cars never have to look for parking and have off-street parking -- but these kinds of places have low traffic anyway, so who cares? In the places where traffic is actually a pain, cabs improve it.