Comment by dashundchen | Hacker News Reader

Comment by dashundchen | Hacker News Reader

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It's apparent through a lot of boring company press releases the tunnels are intended for essentially cars temporarily put onto skates in tunnels.

So then why not a high speed train instead of individual vehicles? You would think the capital cost of a tunnel over it's lifetime (100+ years going by the NYC subways) is not substantial compared with magnitudes more in individual vehicle operating costs.

Not to mention trains have much higher throughput, energy efficiency, less worry over spacing via stopping distance etc over individual propulsion methods, and airports are pretty bursty in terms of traffic volume.

The answer seems pretty clear with the disdain Musk expresses of sharing public space with the average person. https://www.wired.com/story/elon-musk-awkward-dislike-mass-t... (which for me, also explains the obsession with Mars as some sort of refuge from disaster on Earth)

He's clearly focused on more cars as the solution to the urban issues that cars are causing.

> So then why not a high speed train instead of individual vehicles?

This is meant to evolve into a citywide transportation system where you choose your destination at the outset. Each pod can navigate itself, switch tunnels, and wind up closer to your destination than a subway could ever hope to as there will be far more stops (multiple thousands across the city instead of < 500).

Clearly the airport express route is meant to be the beginning of something much larger.

Trains would not make sense for such a system.

Building underground interchanges that include complete grade separation would entail building cloverleaf interchanges underground. Cloverleaf interchanges usually cost somewhere from 500 million USD to 2 billion USD above ground.

Such a system would either be very low throughput or just as bogged down as the roads. Individual itineraries imply low-occupancy vehicles (because how many people from your starting point will go to the same out of thousands of destinations?).

If you assume an optimistic 4 people per vehicle with an optimistic 5 second interval between vehicles (which is probably not safe at the high speeds due to the frequent merges), that gives you ~50 people / minute / lane, or 3000 per hour. A single CTA 8-car train at crush capacity (admittedly uncomfortable) can carry nearly 1000 people.

Now a frequent system with high occupancy vehicles and transfers could work, but that's the same thing as a subway.

The key is that this system can operate in 3D. You can have bundles of tunnels where you need higher throughput, and greater demand can just be met with more tunnels. The focus on small tunnels/cars as the core technology is part of this, since it makes it easier to reach "mass production" scales.

So to first order, you'd have to build as many tunnels as there are road lanes to get the same order of magnitude throughput? I get that there is more space underground, but this sounds completely cost ineffective given that many municipalities can't afford to maintain their roads.

5 second interval seems excessively large if you compare it to car traffic, and that's with human drivers.

Yeah but the cars aren't moving at $LUDICROUS_SPEED and aren't dealing with constant merges from feeder tubes.

So, basically, roads, except that every lane costs as much as a tunnel of the same length, because, well, it is a tunnel.

(Sorry for the excessive commas.)

> The answer seems pretty clear with the disdain Musk expresses of sharing public space with the average person.

Designing a transport system around some guy's phobias seems like a bad idea.

The system described only has a 2k/hour peak capacity. It's unusable as real public transport.

Yeah, why not tether the "skates" together into a train? Boarding individual 8-16 person vehicles seems like a major chokepoint.

The intent is the opposite - having individual cars allows you to parallelize ingress/egress, as long as you have pulloffs at stations (and sufficient elevator capacity). The decrease in trip time from making every trip express (instead of stopping at every station for the fraction of passengers who want to get off) offsets the smaller car/train capacity.

Maybe Musk having some agoraphobic bias is the root cause. Or maybe it's because Tesla doesn't sell trains.

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