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Comment by danielbarla | Hacker News Reader

I think both of the latter approaches make sense in the context of their era. With classical train / subway-style approaches, it made sense to have a bigger upfront cost, so that you could have fewer (but larger) trains. On the other hand, with today's relatively reliable small-scale electric vehicles and automated driving, I can certainly see lots of smaller pods being perfectly viable.

That said, I don't have any particular insight into the field itself; however I do have a respect for Musk's ability to rephrase the problem just slightly (e.g. landing boosters to save costs) and to turn the whole economics of the situation on its head.

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> On the other hand, with today's relatively reliable small-scale electric vehicles and automated driving, I can certainly see lots of smaller pods being perfectly viable.

How? These pods take 16 people, and per the article, only one can set off every 30 seconds. This limits capacity to 2k people per hour (even assuming that it manages the promised numbers, and historically Musk stuff doesn't), which is far less than one would expect of a decent bus rapid transport line, never mind an underground train.

With a 10x increase in tunnel-boring speed, it may be possible to build several parallel tunnels, all serving the same route. In this case, each individual tunnel would be launching 16 people every 30 seconds.

Parallelzation applied to subways.

Or, for 10% more cost, you could build a regular subway and move the same amount of people in much less space. You even reduce the truly expensive part of subways (i.e., stations), since you only have to have a mezzanine that covers two tracks rather than 20 tracks.

Think about it from a redundancy standpoint.

Single big trains get delayed due to any number of reasons - something on the tracks, broke-down train, etc...

With 10 smaller tunnels, they can just be rerouted.

Not really. If the other tunnels are essentially full up with other trains, then there's no space to squeeze in the trains from the blocked line. Furthermore, you'd have to have crossovers in place to enable that kind of routing, and those underground switching crossovers are not going to come cheap.

Or just build longer pods. Or link them together like a train. Can still be narrow.

small pods introduce the insanity of the highway system into spaces meant for trains. perhaps there are some improvements to be made through automation and scheduling of lanes but it seems possible pods would prove to be significantly less efficient when compared to the traditional use of lanes with large vessels that hundreds of people fit into

I guess it depends on just what size vehicles we're talking about. I agree that having tiny one or few person pods would probably not be efficient. But a "10-person cars on rails", type of scenario might not be as insane as you make it sound. Since it neatly side-steps the most complex parts of automated driving, we could have the reality of a well orchestrated fleet of smaller units. These could link up for efficiency on demand (maybe even while in motion), then separate again if they are operating in a complex web. Having a cheaper way of making tunnels feeds back again into the loop. Without doing any rigorous analysis, I can't comment much, but I wouldn't dismiss it offhand.

So, it would presumably be like loading small trams at a ski area--if they had lots of intermediate stops rather than maybe just one. Yes, those work. Everyone is typically also able-bodied enough to be skiing and you have attendants supervising the loading and unloading.

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