Estimate time for Tesla to calc its robotaxi safety

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We can try to estimate how long it will take Tesla to estimate the incident rate of their US robotaxi service.

We can borrow some ballpark stats from Waymo.

Waymo accumulates 1 million miles per week for about 1500 taxis that are L4 autonomous, or about 35,000 miles per taxi per year.

Waymo has about 1 incident per 1 million miles.

Tesla has 10 taxis testing L4 autonomy with onboard safety monitors, so assuming 35,000 miles per taxi per year, Tesla accumulates 350,000 miles of L4 testing data per year.

Assume Tesla needs to accumulate enough miles to observe 20 incidents (this would be near a minimum I would think to have some rigor to estimate something like confidence intervals on the incident rate - feel free to run the exact stats, if you need more detail, or another kind of stat).

Scenario 1
Assume Tesla has the same incident rate as Waymo: 1 incident per million miles.

Then 20 million miles are needed to observe 20 incidents.

At 350,000 miles per year (with 10 taxis), 57 years are needed to accumulate 20 incidents (on average).

Scenario 2
Assume Tesla has 3x worse the incident rate as Waymo: 3 incidents per million miles.

Then 6.7 million miles are needed to observe 20 incidents.

At 350,000 miles per year (with 10 taxis), 18.5 years are needed to accumulate 20 incidents (on average).

Conclusion
To move their robotaxi project faster, clearly Tesla gonna need more taxis and scale faster.

Or maybe Tesla can somehow leverage all of the data from their retail fleet (which maybe would be like having additional safety-monitored taxis), if that data can be equivalent in this way.

A lot of the Tesla retail mileage is highway, so probably much less useful. However, one would still expect Tesla to have a lot of city and suburban mileage from their retail fleet.

With safety monitors present, Tesla would actually have to use disengagement rates (when the safety monitor intervenes before a potential accident) and then somehow estimate what fraction of disengagements would have resulted in an accident of some kind to then estimate incident rate. Presumably Waymo does this as well.

I would be interested to learn of other estimates of this kind.

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Calculating with 10 cars is just silly.

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I think we can already invalidate the comparison based on that assumption. Reports are that there have already been over a dozen incidents since the Tesla rollout - and with far less than 1 million miles.

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Why?

That’s current state, no? And hence their current run rate.

What is an appropriate number of test robotaxis to use for Tesla to estimate this, then?

Suppose Tesla 50x’s their test vehicles in the next few months, to 500 vehicles.

Then they will have a 20 incident data set in about 1 year, assuming an incident rate similar to Waymo.

But they might need to expand their geography and customer base accordingly to fill these 500 taxis and actually get rides to travel 35k miles per year per taxi.

Look, the above can all be wrong, but it’s based on what we know.

It’s an estimation/forecast exercise.

I’m open to alternatives.

I’m ok to be wrong.

Don’t forget to make your predictions here:

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Fyi

I’m using event stats from Waymo, their definition of what I am calling incident:

But definition of incident can vary. City of Austin has an incident dashboard that is a much broader definition including much more minor things.