Tesla safety report and the need for caution - July 2019 update

The latest figures are in the accident rate for cars with Autopilot have improved from 1 accident in 2.91 million miles to 1 in 3.27 million, a 12% improvement over 6 months and reversing the worsening of the accident rates we saw 3 months ago. This is probably statistical noise were the number of actual accidents is relatively low, coupled with some seasonal variation as the northern hemisphere, a region where Tesla are most popular, have been in spring for the last quarter and consequently less ice, less darkness, generally better weather. There's some conflicting reports however that says August is the worst month, we may seem an increase next quarter.

The surprising and most marked improvement is the passive safety results, an increase from 1.58M to 1.76M to 2.19M miles - a 30% improvement.

At the risk of giving the impression Tesla can't win, the improvements in passive safety have massively outperformed autopilot in use, and the ratio now suggests AP is 49% safer than passive safety measures, against the near 100% better performance it was 6 months ago. Both are safer, but the relative improvement of AP, especially when we look at the arguments in the original argument that highlight AP is only used on significantly safer road type and should be up to 4x safer, suggests there is still a long way to go and the advantage and relative safety of AP is falling behind. We'd need more data to be understand the relative numbers for different road types.

We'll rephrase the point. If you are thinking the use of AP is a safety benefit, we don't believe any of the numbers presented by Tesla prove it is, and if anything, the use of AP is now worse relative to simply relying on the passive safety systems.

Our original article

Teslas Vehicle Safety Report stated some interesting, and we use the word lightly, facts.

This is essentially trying to suggest that the use of AP results in half the rate of accidents per mile driven than Tesla not on Autopilot.

Lets break this down a bit.

Superficially the Tesla figures could therefore look quite worrying. Their software is 2x as safe as not using it, but as it is largely used in the context of roads that are historically 4x safer than other roads, it could be argued they should be 4x as safe on a like for like basis, or expressed differently, given the road type it could be argued that AP is half as safe as expected. The mathematics here are simplified, but we trust it illustrates a key problem in interpreting the Tesla data.

We can add in some additional data points. Teslas are expensive cars and its also not unreasonable to assume that the demographic of the typical driver is someone in their 30s and above. These are by far the safest class of drivers per mile with accident rates up to 4x safer than the worst age demographic according to AAAFoundation.

There's also an article on general safety features available on modern cars, some of these features only becoming more common place in recent years such as lane assist and so rare on many older cars. We saw material safety improvements when seatbelts became standard and general reduction in accident rates due to ABS and stability aids, we're now seeing a similar increase from these new features. Forbes top 7 car safety features goes into a little more detail.

Technology improving safety is far from new, the insurance industry for highway safety found a 40% reduction in single vehicle accident rates from the introduction of stability control, technology which some cars still don't have and are part of the baseline statistics, although admittedly the number without is increasingly small.

But lets conclude positively

We do not fully subscribe to any argument on the relative safety of Tesla and Autopilot as the data available is far to weak and any number of assumptions can be made. Through the addition of a small amount of additional data to add context, the picture becomes very different and the argument can be skewed to any political agenda you wish to portray.

It would be beneficial if Tesla put more information out there and allowed some impartial and detailed analysis. They should be mindful that when putting out incomplete data sets that give a superficial view on safety it can do more hard than good and potentially give a false sense of security. We have seen too many instances of people abusing Autopilot, and in a number of occasions with fatal consequences. The suggestion that Autopilot is twice as safe as without must not be taken as an excuse to rely on Autopilot.

But lets take the positives, firstly Tesla are one of the first companies to publish any data like this that we are aware of, that's to be commended. Secondly, the cars appear to be able to cover many more miles between accidents than the average, whether it's the passive safety systems that are also on other similar priced and aged cars or driver demographic we don't know, but if you're in a Tesla, you're safer than average. And thirdly, Tesla like several other car manufacturers, are continuing to innovate and push the bar higher, and while we could be sceptical on the current metrics, merits and safety of the systems, innovation and change is how improvements will come about. For that we should all be grateful. Just don't abuse it.

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We are Tesla owners and in general supporters. We don't hold stock in Tesla, nor do we short Tesla stock. Our views are our own, based on data points and research that we conduct ourselves. Our goal is to take an impartial view as far too many organisations are either extremely pro or anti Tesla.

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