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Comment by Sheeny96 | Hacker News Reader

Why are the cars so big? Wouldn't it make sense to have a bunch of much smaller, single person vehicles?

Tesla Cybercab has about three or four times the efficiency and like a fifth of the price by having smaller, two person vehicles. Indeed, the vast majority of trips are taken by single people and it's ridiculous to have a giant machine for them. It would also be okay to have a handful of larger, Model Y-sized vehicles for the multi-person trips.

To actually answer your question: Part of the reason why the Waymo cars are so big is because they got a deal on buying all the Jaguar I-Pace vehicles, which checked several boxes:

* Electric vehicles and hybrids are preferable for self driving cars as they have robust electrical power for the sensors and compute

* Larger minivans or SUVs are preferable for both development work and early scaling up where you can't afford to have both smaller and larger vehicles

* The I-Pace wasn't selling well so they managed to snag the whole production batch

* Though Jaguar isn't exactly known for their great reliability and electrical systems, the I-Pace, manufactured by Magna Steyr, is actually decent

The first two reasons are why the Chrysler Pacifica Hybrid, the only hybrid minivan sold in the US, was so popular for early self driving car efforts (including with Waymo) in the 2010s.

That said, Waymo's Ojai is somewhat more space efficient than the older I-Pace. They also have the Ioniq 5 coming.

> Tesla Cybercab has about three or four times the efficiency and like a fifth of the price by having smaller, two person vehicles

I read this as Tesla Cybertruck and was mightily confused for a minute.

Looking it up in Wikipedia I see it has no driver support (steering, pedals, etc). Is that even road-legal?

I have one of the most inefficient EVs and it's only 2.4x hungrier than the cybercab. It can comfortably carry 6 adults. I've been in Tesla 3s as Ubers before. They only need 31% more energy than the cybercab.

If the cybercab was 1/5 the price it would be $14k. It won't be $14k.

The Waymo I-Pace is much less efficient than the regular roadgoing I-Pace. One X user posted a pic of the dashboard of a Waymo with 111,000 miles on the odometer, and it averaged 1.0 kWh per mile [1][2]. This is about 2.5x worse than the EPA rating of a normal Jaguar I-Pace. Probably the difference is because the Waymo has tons of compute and the sensors have a surprisingly large impact on aerodynamic efficiency. I was being generous to the Waymo in my original comment. If we compare the actual rating of the Cybercab at 165 Wh per mile, it would be 6x as efficient.

Also, whereas the stock Jaguar I-Pace was $70k, the Waymo one with all its sensors and compute have estimates ranging from $150k to $200k. In a comment made in late 2024, Waymo CEO Dmitri Dolgov mentions that the sensors and compute themselves cost $100k [3].

> The equipment on Waymo’s fifth-generation robot taxis — electric Jaguar I-Pace vehicles — costs as much as $100,000, Dmitri Dolgov, Waymo’s co-chief executive, said on a podcast in February.

That is the same generation as the current I-Pace fleet that makes up the majority of Waymos.

[1] https://eletric-vehicles.com/waymo/waymos-retrofitted-robota...

[2] https://x.com/niccruzpatane/status/2073967445509882286?s=20

[3] https://www.nytimes.com/2024/09/04/technology/waymo-expansio...

Referring to the example from the Twitter post you cited, wouldn't the KWh per mile simply be a lot higher because these vehicles are engaging in much less efficient travel overall? City driving itself is often pretty inefficient because of all the stopping and going, and these vehicles likely are driving in a lot of the rush hour traffic and high density areas everyday. Not to mention they probably idle around a lot more than a normal persons car would in a day.

So wouldn't that be the reason the figures would look 2.5x worse than the regular Jaguar? I'm sure there are other factors of course since running the computer systems, lidar and all the other features will also consume more power, so I'm sure from a baseline it will be less efficient anyway, I just think because of the kind of driving it engages in, this will make it also look far less efficient.

Possible, but EVs tend to be more efficient in city driving than highway driving, thanks to regenerative braking and the fact that the dominant form of energy loss, air resistance, scales quadratically with speed.

Depending on conditions, heat or AC can consume up to 5 or 6 kW in extreme weather and a small fraction of that in milder conditions. The most efficient speed of an EV is hard to pin down. If all fixed loads could be turned off, it would be most efficient at the slowest possible speed but with HVAC and compute loads present, the most efficient speed is around where the aerodynamic load is equal to the fixed load. That's still likely to be rather slow but the idealized math that gives this optimum is for steady-state operation. There is a round-trip loss for regen, so there is still an advantage to steady operation even if it is not as big as with ICE cars where no kinetic energy is recovered.

My guess for the poor reported number is excessive idle time w/ HVAC and compute stuff on within the trip interval.

Weather can be arbitrarily extreme, but:

1. My whole house AC only consumes 3 kW when the outside is really hot, like 36 degrees C, and I seriously doubt that car AC can consume 5 or 6 kW

2. With hotter weather, the density of air also decreases and air resistance is reduced. This partially offsets the need for extra cooling (of both the occupants and the battery), so range is only perhaps impacted by 5-10%.

Max power consumption of the compressor in my car is 5.5 kW (see pg. 28 of https://www.scribd.com/document/783343319/MEB-220169869). The blowers would draw additional power. These values would only be hit in extremes and I'm not certain the compressor can run at 100% duty cycle.

Regarding the dashboard pic - that's a trip computer display (see the "A:" and https://www.youtube.com/watch?v=hAdzIuAB3-g) which can display a large range of values depending on the history since the trip was last reset. That fact is recognized in the article you posted but buried in the middle. Using the power estimates in the article won't get you to the inefficiency shown in the trip computer either and aerodynamic changes only make sense if the vehicle is making mostly highway trips, which maybe? My EV, less efficient than the i-Pace (because it's big tall van), in it's first 10k miles averaged 2.5 mi/kWh or 0.4 kWh/mile at an average speed of 36 mph. That works out to around 14.4 kW average load. Adding 3 kW to that for compute (upper end of estimate of one source in the article you linked) pushes that number to 17.4 kW, which would change my efficiency number to 2.1 miles/kWh - still double the i-Pace trip computer. So I don't trust that number as a foundation for any conclusions.

And if the cybercab is cheaper because it doesn't include the sensors needed to actually see the world around it, that's not great either.

The cybercab would be almost perfect if it weren't for it's low height. It's easier for the elder to get into and out of taller vehicles.

The Waymo Ojai is great for this: large entry, low floor, high ceiling, high seats

Yeah it's definitely better in that regard, but it has the other disadvantages: oversized for single passengers, and also personally it feels like public transport, it's the opposite of luxurious.

Why would it make more sense? It isn't like a car half the size would cost half as much, but it would severely limit the capacity. Now, you can get a waymo for 1-4 people, but if some (or all) were single occupant, you would be limited.

Being smaller does not help that much much in cost per mile, but has a big cost for functionality.

SFC costs don’t scale linearly with volume or number of seats.

The cameras, LIDAR, and sensors are all fixed costs. You need them on even a single-person car. And they’re extremely costly.

It would make more sense to make them even bigger, and to have one vehicle service many people. Maybe they could even be linked together for efficiency, and put on rails so the self driving is super reliable.

And make those rails go to any destination, on any schedule.

Yes! Let's build dense, walkable destinations around transit stops with regular service.

The smallest single-person motorized vehicle is a motorcycle. Leaving stability aside for a minute - one of the issues with electric motorcycles is that the batteries are too small to have range that most riders consider sufficient.

If you have a large enough battery to deliver sufficient range for an electric taxi (driving around most of the day, hopefully, if it is well-utilized), with 4 wheels for stability... I doubt that you could really get significantly smaller where the smaller size would make a big difference.

I’m thinking that since 2015. Like BMW C1 just with doors on the side and a bit more security. This would approx allow 3-4x as many travellers on a given route compared to traditional cars.

A C1 with more security, meaning more material and air between you and a potential high-speed obstacle, is called a car and is sized like one.

Fair point.

I still think you could build single person cars that are more secure than traditional cars and use less space and energy

Americans are fat, they don't fit.

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