[vonmoltke]

First off, you cannot ignore the $876mm capital portion of the budget; that money needs to come from somewhere.

Second, that $500mm covers every employee of BART. The administrators, maintenance personnel, police, and other non-operator functions do not go away. Without knowing what portion of that line item goes to operators one cannot make a judgement on how much cheaper the system would be without them.

[zamfi]

Of course you're right; my comment was mostly tongue-in-cheek. Actual train operator salaries probably cost BART about $50m annually, not $500m. In both the cases of BART and private cars, the money to pay for tracks or roads comes from taxpayers. The trains themselves are now 40+ years old, and are finally being replaced at a cost of ~$300m this year. Grandparent post specifically talked about operating costs though.

All that said, trains are basically the most efficient mode of transport from a (number of drivers) / (number of passengers) perspective.

But speaking seriously for a moment:

- Lyft charges riders about $2/mile in the Bay Area [0] before fees.

- The IRS lets you depreciate your vehicle at a rate of $0.545/mile.

- A reasonably efficient car burns ~40 mpg on freeway, at $3.50/gallon that's ~$0.09/mile.

So, of the $2/mile the riders pay, about 1/3 of that is costs associated with purchasing and operating the vehicle (according to IRS estimates) and fuel.

If we eliminate the rest via autonomous driving, and taxis became 65% cheaper, I suspect many people would make much more use of them.

[0]: https://www.lyft.com/pricing/SFO

[perl4ever]

Utilization rates are 50-58% for Uber or Lyft. When you take it into account that a taxi is not en route 100% of the time, and add the cost (interest, depreciation) of a much more expensive vehicle, I think your 65% savings go up in smoke.

[zamfi]

Sorry, I'm not smart enough for this comment to stick with me. Could you walk me through how 50% utilization means the savings go up in smoke?

The most compelling thing I can pull from your comment is "autonomous cars will be 3x as expensive as regular cars (at least), so you won't save anything". That may be short-term true, but is almost certainly long-term false.

A 50% utilization compared with 100% utilization makes almost no difference in vehicle cost structure -- if anything, it actually increases the labor fraction of taxi cost.

If you're driving your car 50% of the time, then wear and milage is the dominant depreciation factor (rather than age). But a human sitting around doing nothing but waiting for that 50% of the time doubles the labor (time) cost of the service, suggesting an even greater savings from eliminating the human driver.

What am I missing?

[perl4ever]

I was assuming humans and self-driving cars both get revenue from riders, but don't get paid in between. And I'm interpreting utilization as the percentage of the time that riders are paying.

[zamfi]

The human's time has a cost, and even if the rider doesn't explicitly pay it, it is factored in to the labor cost of the driver.

The machine's time cost is time-based depreciation, which is pretty low.