Really, I don't get it.
There's no reason that these vehicles should be more efficient in use than personal vehicles. Given the replacement and maintenance schedules that I see on public transport today, I'd guess that they're more likely to fall behind the standards of efficiency of the personal vehicles owned by the people that might consider switching (i.e. Sam Suziki, not Sarah SUV).
So the benefit is a reduction in the "capital" costs of building more vehicles? Uh, wait, how many people are going to give up their personal vehicle entirely in favour of one of these? I might take the bus to work every weekday (if there was a bus to take...), but I damn well need a car for the evenings and weekends.
Also, doesn't rush hour account for a major proportion of the traffic on the roads? We'll still need a shedload of these things to cover that. Crikey, and what happens when one of them breaks down (or the local kids put a traffic cone in front of it when it doesn't have a passenger in it)? Can it pull itself off the road? Can the other vehicles route round it? Best case, it's no better than the current situation.
The only major effect that I can see of these things is to put some taxi drivers out of jobs, and provide a nice revenue stream to the manufacturers and maintainers of these devices, as they get regularly wrecked and vandalised.
So, can anyone tell me what I'm missing?
"Exterminate all rational thought." - W.S. Burroughs