You have to dig up and destroy hundreds of miles of walkways.
You have to replace brick, concrete and tiles with hundreds of miles of very, very expensive electromechanical technology.
You have to do this in TWO directions.
You have to hire thousands of workers, technicians and engineers.
You have to fund the development of the technology because it doesn't exist for this application.
You have to provide power, lighting, etc.
If this is in snow country, you have to provide a small army of snow removal trucks and crews to keep the darn things clean. Even then you'll still pay to move tons of snow, which won't be cheap.
You'll have to widen sidewalks in lots of places in order to accommodate all forms of traffic and work around existing infrastructure (subway station entrances?).
You'll have to have medical services available because you will have people getting hurt as they fall off the thing and do stupid stuff at 10 miles per hour.
Liability is likely to be huge.
And, of course, there is no practical way to charge for usage so we are probably going to sock everyone with yet more taxes to build yet another bullshit project nobody is going to use.
If the context is to replace "crosstown buses" you are talking about tens to hundreds of miles of sidewalks and all of the organization, infrastructure, cost and support to take something simple (buses and bus routes) and turn it into something complex, pointless, questionable and unlikely to really work.
The cost of such a ridiculous system would be staggering. Not sure why anyone who reads HN would need this spelled out.
I think you are presuming a method of implementation and routing with some location in mind where this would not be that applicable.
I disagree most strongly about the need to dig up and destroy walkways. We have 3 dimensions to work with - to go up, or, down. In any case I would see this analogous to a public urban rail system such as a metro or a tram.
I don't see it as a big issue to dig a tunnel for this - lots of cities implement rails and such that go wherever public transportation is needed.
The only argument which I agree is the biggest hurdle - which is actually an unknown - is how to make the system sufficiently robust so you don't need an army of engineers to maintain it. The fact that there are no known robust systems is not a good enough argument. Lots of mechanical systems were in the development over a century after someone figured out how to make them as practical to make a major impact(steam engines, automatic weapons).
How robust is the most robust implementation possible and how expensive it is are the two major questions to my mind. If it's too expensive to maintain - then it's too expensive to maintain.
The point you should be agreeing with is that regardless of how you build it --dig a tunnel, rip-up the sidewalk or go vertical-- the cost of such a system defies a comparison to a simple fleet of buses by a huge margin. I would venture to say one, if not two orders of magnitude.
I mean, the thing is ridiculous to such a degree that it is surprising to see anyone arguing in favor of it.
Buying a fleet of electric buses would make far more sense than this insanely ridiculous idea.
You have to dig up and destroy hundreds of miles of walkways.
You have to replace brick, concrete and tiles with hundreds of miles of very, very expensive electromechanical technology.
You have to do this in TWO directions.
You have to hire thousands of workers, technicians and engineers.
You have to fund the development of the technology because it doesn't exist for this application.
You have to provide power, lighting, etc.
If this is in snow country, you have to provide a small army of snow removal trucks and crews to keep the darn things clean. Even then you'll still pay to move tons of snow, which won't be cheap.
You'll have to widen sidewalks in lots of places in order to accommodate all forms of traffic and work around existing infrastructure (subway station entrances?).
You'll have to have medical services available because you will have people getting hurt as they fall off the thing and do stupid stuff at 10 miles per hour.
Liability is likely to be huge.
And, of course, there is no practical way to charge for usage so we are probably going to sock everyone with yet more taxes to build yet another bullshit project nobody is going to use.
If the context is to replace "crosstown buses" you are talking about tens to hundreds of miles of sidewalks and all of the organization, infrastructure, cost and support to take something simple (buses and bus routes) and turn it into something complex, pointless, questionable and unlikely to really work.
The cost of such a ridiculous system would be staggering. Not sure why anyone who reads HN would need this spelled out.