First, note my premise- "as part of an autonomous transportation system". This is imagining that a couple decades down the road, transportation in general has

First, note my premise- "as part of an autonomous transportation system". This is imagining that a couple decades down the road, transportation in general has been transformed and doesn't work the same way it does now. You don't necessarily ride in a car door to door, unless that makes sense. If it doesn't make sense (for example, new construction hasn't emphasized roads, but instead 'segway-ways'), then you travel hub to hub and then finish that last quarter mile or so on segway. See something like Masdar City ( http://www.wired.co.uk/magazine/archive/2013/12/features/reality-hits-masdar http://www.wired.co.uk/magazine/archive/2013/12/features/rea... ), but with a segway-like system instead of bulky personal cars. Entirely possible to imagine car-less towns, connected by public transport to the rest of the world, and segway like transportation inside the town.