[stretchwithme]

I think a lot of that will happen.

But what technologies power the vehicles or enable the roads are secondary. The efficiencies gained by reducing vehicle size will slash costs.

A great many people will commute in a single seat vehicle with 50 horsepower if its a quarter of the cost per mile. Especially if they aren't stuck with it the rest of the time. As long as they can just as easily get larger vehicles for other occasions.

As far as alternatives to conventional roads, we already have them in major cities. Some are elevated and some are underground. Today only mass transit uses them, but I fully expect robotic cabs to destroy mass transit. Even people who don't value convenience will ultimately go for them. So subways and elevated railways, once abandoned by trains, will be converted so they can be used by individual vehicles.

[seanp2k2]

I disagree. See "one lane road" problem. Throughput will be very low and average speeds for urban areas will be close to that of bikes, at best, unless you're doing on/off ramps.

Also, re: many smaller cars... who will purchase/maintain all those? We don't have the infrastructure to support that on many levels.

Personally, I think a system like that in /I, Robot/ is much more likely.

[stretchwithme]

People will operate businesses that own their own cabs or individuals their own personal vehicles. Just as we do now.

And the infrastructure we have now will continue to operate.

How will such an infrastructure be built and be operated. Its a mystery. But its already been done by private enterprise.

As to why only one slow lane could be used, I don't see why that would be. Perhaps you could explain. We have many lanes operating now and robotic vehicles would simply use the same lanes.

Perhaps PRT has these limitations. Robotic vehicles that operate like the vehicles that operate like the vehicles we already have wouldn't.

Of course, we do not yet have robotic vehicles that can be trusted to operate in rain or other extreme conditions and that can discern their environment well enough to be safe.

But once we, there's no reason to follow the PRT pattern. We'll simply follow the patterns we already have. Only with much more sharing (cabs) and much more efficiency.

[FrojoS]

This is a great point that I haven't heard yet. Reducing the cost by a factor of 4 might be a bit to optimistic though.

[stretchwithme]

It may very well be overly optimistic.

But many features of today's automobile are there because of human needs for performance. Optimize for efficiency for a moped-like 3 wheeled vehicle and you may get something completely different.

  http://www.niutoday.info/2011/09/14/supermileage-team-proves-nation’s-best-again/

I'm not saying cars will actually be like this, but robotic vehicles won't need mirrors or more than one seat or even a steering wheel. A lot of things are could change.