Does using AP increase safety? We can infer Elon thinks it does, given his comparison of the death rates on roads against Tesla’s one fatality. But I’m still raising this question because I think 1) it’s important and 2) it’s not so simple. Unfortunately it’s also likely to be contentious. I’m not asking “Is using AP safe?” because that clearly depends. It depends on the circumstances of its use. Obviously, turning on AP at random during a drive and letting it run without further intervention will probably result in a crash. None of us would do this, but the point is that the safety of AP is a function of the combination of the driver and AP itself, since 1) AP is only designed to be turned on in certain settings (for example, divided highways) and 2) it sometimes needs driver intervention even in those settings. In particular, the driver must be ready and able to take control immediately, and most of us have plenty of personal experiences where such quick intervention was necessary for one reason or other. So the safety of AP depends on the conscientiousness, attentiveness and skill of the particular driver using it, which is why “Is using AP safe?” isn’t meaningful. What is meaningful is a comparison of that driver’s projected accident rate using AP, given the choices they make when using it, and their projected accident rate just driving the same routes by themselves. Or in terms of statistics, the meaningful comparison is between the accident or death rate of a population of drivers using AP, and a population of equally conscientious, attentive and skilled drivers who are driving Teslas without using AP over the same routes where the others use AP. This comparison would show whether using AP increases safety. The problem is that this is nothing like Elon’s comparison. First, AP is “intended for use only on highways and limited-access roads” (according to the manual) and I assume our AP use is at least skewed in that direction. I’m having trouble finding statistics on fatalities per vehicle mile on interstates, but I assume divided highways are significantly safer (which makes the comparison for AP tougher) than all roads in the aggregate. Second, Teslas are intrinsically safer than the average car, so there would be fewer deaths in the comparison group of non-AP cars if they were all Teslas. Also, overall fatality per vehicle mile statistics include motorcycles, which are less safe. Third, I expect the average Tesla driver is a safer than average driver, even when when they drive ICE cars, simply because their being able to afford a Tesla means they are probably older. The result is that the figure for fatalities per vehicle mile that Elon should compare to is significantly lower than the nationwide average number. Of course Tesla’s one fatality isn’t statistically meaningful anyway, but Elon’s comparison is not a good argument that using AP increases safety. But what about other arguments in favor of AP being safer? One could argue that if AP is used exactly as instructed in the manual, then it is extremely safe: safer than driving. But that’s because the driver would always cover for AP’s mistakes: the manual requires that we must “always be prepared to take immediate action.” The difficulty is that I suspect that about the only human capable of always being prepared to take immediate action – who takes no extra time to refocus their full attention – is Sully Sullenberger. So the relevant comparison against AP is Mr. Sullenberger driving an intrinsically safe Tesla down a limited-access highway, which is about as safe as safe can be. I don’t see how AP being used exactly as instructed can be safer than that. But then there are the rest of us fallible mortals who are trying to do what the manual wants within the psychological limits of attention and skill. So for us fallible drivers, which alternative is riskier: 1) correcting the wheel in an instant when we are completely surprised by AP balking at a tight curve, an asphalt patch covering lane lines, a reflection driving toward the afternoon sun, or the crest of a hill; or 2) driving ourselves through a tight curve, over an asphalt patch, into the afternoon sun, or over the crest of a hill? I think there is no question that (1) is much less safe than (2). In other words, AP reduces safety in these cases, it doesn’t increase it. But these cases need to be balanced against the cases where AP would be safer, which is where the driver is sleepy, or loses attention because of a monotonous road, or because of a long stretch of stop and go traffic. Which way does the overall balance go? Is the safety increase in these situations enough to boost overall safety beyond that of driving one's self? I don’t know, but I doubt it. I definitely think that driving the car one’s self is currently (under 7.1) slightly safer as long as these conditions don’t apply. All of this is not meant as a criticism of Tesla. They are trying doing great things in automated driving, and I believe they will eventually succeed. So I guess my conclusions are: 1) Except for sleepiness, monotony and stop-and-go, supposed safety is not the reason to use AP. Convenience is generally what would justify its use. 2) The safety focus for using radar in 8.0 is a good thing, because that will shift the balance to some degree. It needs to be shifted because AP is not now intrinsically safer than driving. 3) I hate to say it, but enhanced nags to force us to hold the wheel are probably a good thing. The argument against nags would be stronger if AP was as intrinsically safe as Elon says, but it isn’t. I’m looking forward to 8.0. What do you think?