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This could make cabs and buses more fuel efficient by changing the aggressiveness most drivers have in acceleration.
A cab is not fuel efficient in that it has to drive to you first.
Neither cabs nor buses are convenient when traveling to or from remote locations.
Neither buses nor cabs are useful for transporting large, heavy, or awkward items in comparison to a car that can let its back seat down, truck, or van.

That's not to say there aren't also negatives to moving to such a technology.