A news story today talks about alarms to alert drivers before they leave kids unattended in potentially-hot cars. As of this writing 61% of responders to their poll think such warning devices should be required in all new cars. The article quotes someone saying that, hey, your car will tell you about your headlights being on, and isn't this more important?
We can take as given the riff on parental responsibility, right? It's not Toyota's fault if your kid gets left in the car, but that's clearly where the suits will be directed when one of these systems fails. That's not what this post is about.
I suspect that most of those 61% don't care about the difference between worst-case cost and expected cost. While leaving a kid in a hot car for an hour is much much worse than leaving your headlights on for an hour, I submit that the probability is much much lower, or there'd be a lot more news stories about it and a lot fewer calls to AAA. The expected cost of the headlights is higher and carbuyers care, and that's why that alarm is standard equipment. No one but the market requires that makers put it there.
Speaking personally, the expected cost over, say, the next decade of my leaving a kid in my unattended hot car is 0. The expected cost of my leaving my headlights on is some positive fraction of $100 for a new battery and several hours of my time, at least one of which comes at a time when I, demonstrably, wanted to be somewhere else. 61% of poll responders would say "tough noogies" to me and wouldn't care if adding this device costs me hundreds of dollars. (I don't know what it costs.)
If that's what those voters truly believe, then they do not go far enough. If the goal is to prevent the deaths of those who can't see the danger or get out of the car themselves, then clearly it's not just about kids. Some adult passengers are unable to care for themselves and could die in hot cars too. I think it's actually more likely that an adult suffering from dementia would be ignored by passersby than that a kid would be. We don't think it's unusual for adults to sit in parked cars. Isn't gramps at least as important as an infant?
I predict that I'll get few takers from among the 61%; they would rightly say "you can't prevent everything". Yes, exactly. And given that, you have to cost-justify, and not just emotionally justify, the burden you would place on everyone else. Here's an idea: if you want a requirement, require that the device be built into the car seat, not the car. It'll be more expensive to do right (and be amortized over fewer buyers), but, well, it's the price we pay for safety, right?
Am I missing a sound argument in favor of requiring unattended-child alarms in all cars, or do all arguments boil down to "a possibility of one child's death is worth the certainty of $X in increased cost for everyone"?
There's lots of discussion in the comments.