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Peter Robinson's avatar

I wrote the longer post below in response to your assertion that redundant vehicles need to be cruising around. I have improved some of the calculations just now. Did you read it?

>>Household vehicles were driven an average of 64.6 minutes on a typical day in 2022 (including all trips made that day) and parked for the remainder of the time (95%).<<

https://www.energy.gov/eere/vehicles/articles/fotw-1356-august-19-2024-household-vehicles-were-parked-95-typical-day-2022

It seems clear to me that Waymo should prepare for peak demand. Driverless cars are fundamentally different from taxis with drivers, because there is no driver to pay. Owners of private automobiles are not losing sleep because their cars are parked 95% of the day. And they're not worried about the interest on the money they paid for the car which continues even when the car is not in use. The decision to purchase a car and bear that interest has already been made because of the utility of having a car available when they want it. After that decision has been made, the only cost that owners of private vehicles are concerned about is maintenance. And vehicles that are not moving are not degrading. 

So if private owners are quite happy with a situation where their vehicles are not being used 23 hours of the day, than Waymo should be happy with a situation where their vehicles are used only half of the day. 

>>What do you do with redundant vehicles during the off-peak? Why, you have them cruising the streets, so that customers who would otherwise have to wait 8 minutes for a pickup instead wait 4. <<

I see no reason why they need to be moving around when unoccupied. They just need to be spread around the city in a smart way. Yes they need a parking place, but parking unoccupied driverless vehicles must be a much smaller problem than parking all the vehicles for the commuters into the city.

Let's imagine that the goal is five-minute response time to a call. As a potential rider, 5 minutes seems quite reasonable to me. Now Waymo (or whoever) needs to have enough unoccupied vehicles that even at peak demand there is still at least one waiting vehicle within 5 minutes of every point in the city.

I can imagine Waymo buying a city lot that is vacant or covered with less valuable real estate. They excavate the lot down about 12 ft and build a basement with a ramp to the surface. Then pour a concrete roof over the basement and build a commercial establishment on top (or a park etc.).

>>The number of cars that can park in a city lot depends on the lot's size, layout, and whether it's designed for efficient parking or includes landscaping and walkways. A standard acre can hold roughly 144 traditional parking spaces, but practical layouts typically accommodate 100-115 spaces. <<

>>As of 2024, Waymo's fifth-generation robotaxis were based on Jaguar I-Pace electric vehicles augmented with automatic driving equipment that according to Dolgov costs up to $100,000.<<

Rounding down, lets say 100 spaces for driverless cars (DVs). Each car must be connected to a charger. Since they are parked by robots, the margins can be very tight. So 100 vehicles would actually require much less than an acre.

Now Waymo needs one of these basements within a 5 minute drive of every point of the city.

>>During rush hour, city traffic speeds typically drop significantly, with average speeds ranging from around 10 to 20 miles per hour, depending on the city and time of day.<<

We definitely need to be conservative in this case, so assume 12 miles per hour. One mile every 5 minutes.

Now we need a grid of basement parking lots every 1.5 miles in two dimensions. (Visualize a square 1.5 miles on a side with a parking lot at each corner: most of the points within the square are no more than one mile from a corner. A point in the center is 1.5 miles from a corner when following a rectilinear path. The unlucky client in the exact center of the square must wait 8 minutes for pickup.)

That works out to one parking lot per 2.25 square miles. Underground parking means zero usurpation of commercial/living/recreation space.

Imagine a city of 100 square miles. That's 44 parking lots (@ $10 million per) and 4400 DVs (@ $100,000 per with cost reductions) to provide 5-minute response time.  (Less than $1 billion total -- cheap!)

Quite a bit of slack there: you can go from 100 parked vehicles to 1 parked vehicle and still provide 5-minute response time.  Of course at rush hour, riders are constantly exiting DVs and those randomly-spaced vehicles can immediately respond to calls. So the average pickup would be less than 5 minutes at busy times (and at slack times, average speed would be greater than 12 mph). Also note that when a vacated DV is not needed, it goes to the nearest parking basement. No need to return to where it began.

Sounds good to me.

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