[daemonologist]

There was a CityNerd video (which you may take or leave in general, but I found the anecdote interesting) in which there appeared to be one vehicle in service on the entire system: https://www.youtube.com/watch?v=VPjODKUxV5g

I assume though that they would adjust the capacity depending on time of day and whether there's an event or something going on, to some degree.

[themafia]

> adjust the capacity

It's a single lane tunnel and is thus one way. The parking are can only hold so many waiting vehicles and queued passengers. Their options for adjusting capacity are severely limited.

Then you consider what might happen if the lead vehicle in a convoy becomes disabled, or worse, starts on fire.

It's the same reason planes are safer per "passenger mile traveled" but aren't as safe per "total journeys taken." If you crash a plane you stand to injure or kill hundreds of passengers at once.

[1718627440]

> It's a single lane tunnel and is thus one way.

Maybe they should have asked some railway engineers. Also why throw away the benefits of cars over railway when you inherit non of the benefits.

[antonvs]

> there appeared to be one vehicle in service on the entire system

I watched that video the other day, pretty sure it didn’t say that. What it did point out though is that in most of the system, other than the one main line, there’s just one single-lane tunnel so that when a car is in a tunnel going one way, cars going the other direction have to wait to enter the tunnel until the tunnel is clear.

The title of the video seems pretty accurate: “The Vegas Loop Is Getting Progressively More Stupid.”

[Calavar]

He does say that around 5:32 in the video. He says his driver told him there were two cars on the loop that day, and the other car wasn't in service because it was being used for training.

[duxup]

When he rode his driver told him there should be two cars operating at a time but one was training and couldn't take riders, so there was just one car running.

[tallowen]

Thanks for sharing this, I had understood prior to this video that the combo of self driving tech + dedicated tunnels might have capacity that rival a light rail system like Seattle has but that's clearly not the case in the current system. I'm curious why more of the autonomous driving tech isn't being used in what I might have thought would be an "easier" place to do it.

[Veserv]

If they have autonomous driving technology that works for “harder” problems, then why do they not use it for “easier” problems? You answered your own question; it does not work safely for those “harder” problems.

Zoox has permits to operate autonomously on Las Vegas streets. Tesla is unable to get permits to operate autonomously on isolated, one-lane, one-way streets with no pedestrians, cross-traffic, or even vehicles not under their control. That should tell you everything you need to know about how far reality is away from their corporate puffery.

[jcotton42]

> had understood prior to this video that the combo of self driving tech + dedicated tunnels might have capacity that rival a light rail system like Seattle has but that's clearly not the case in the current system

Not to disparage, but how did you come to that conclusion? A train will always be able to fit more people/m^2 than several cars of equivalent length, due to things like ability to stand, not needing to have multiple engines and trunks, etc.

[tallowen]

> Not to disparage, but how did you come to that conclusion?

I did some math and you're clearly right. I think I imagined that with driver-less vehicles leaving much more frequently (10s per minute) one could catch up to the capacity of a small light rail system but that's clearly not the case. I had imagined that _maybe_ it could be an approach for a lower capacity system in the future.

My math as someone who is not knowledgeable in how to get this data is as follows:

In Seattle is running 4 car trains at 8 minute headways at peak which works out to 7500 people per hour at crush load (4 cars, 250 people per car, 7.5 times per hour). This would require 125 vehicles with 5 seats leaving every minute which is clearly impossible.

Looking at Portland's MAX, it looks like they often run 2 car service with 160 passengers of capacity each with service every 15 minutes so 1280 people per hour (2 cars, 160 per car, 4 services per hour).

1280 people per hour could be served by a 5 seat vehicle leaving every ~15 seconds. This I suppose is what I had expected would happen when I tried to imagine the best case scenario for this service.

[zimpenfish]

> In Seattle is running 4 car trains at 8 minute headways at peak which works out to 7500 people per hour at crush load (4 cars, 250 people per car, 7.5 times per hour). This would require 125 vehicles with 5 seats leaving every minute which is clearly impossible.

7500 isn't that high - the Manchester Metrolink did 46M user journeys in year ending March 2025 (~5250/hour assuming 24/7 which it isn't.) Docklands Light Railway did 97.8M (~11000/hour ass.24/7)

Numbers from https://www.gov.uk/government/statistical-data-sets/light-ra...

[everforward]

> I'm curious why more of the autonomous driving tech isn't being used in what I might have thought would be an "easier" place to do it.

There's no real need in a static environment, and much simpler ways to do it. Children's toys can follow a line painted on something; they just need proximity sensors and a basic signalling system (RF or also painted on the road) for where to stop and done.

There's no real need for the car to "see" beyond "am I going to run into something" and they operate at speeds where stopping is very feasible.

They're also a bad rival for light rail because they already have to dig a tunnel and the conveyance operates on a fixed path. They picked a domain that light rail is already incredibly good and efficient at.

[kevin_thibedeau]

They come to the surface to switch tunnels and Tesla FSD is not a viable technology for automated driving beyond a sunny highway.

[duxup]

It's hilarious how the quality of stops just degrades until you just get a typical car taxi pickup spot ...