I'm not sure how the latter are unconscious: people are generally aware (a) whether they are sleepy (b) how much sleep they've had recently and can use that to make decisions.
It seems that in case of alcohol we've decided on a proxy for its effects (BAC), while for some reason we haven't decided on any similar proxy in case of sleepiness and left it up to the drivers to be responsible.
I don't know how common accidents due to sleep deprivation are (and can't even phrase the question well, because I know of no good proxy for the condition). I expect accidents caused by falling asleep to be a minority of those (because sleep derivation really messes with reaction time and with ability to spot motion on the edges of FOV). So, sadly, I can't tell how good the "please be responsible" approach is for sleep deprivation.
Do you expect this approach to work singularly badly for infection containment for some reason, or work badly in general?
@augieray Hmm... we probably (hopefully) have some data about this due to discussions around occupational driving minimal rest periods length. I will try to see what they used to estimate reasonable lengths there.
@robryk We do a lot of things we shouldn't that endanger others. I'd hope we'd strive to be better--especially for something where we can consciously decide to put on a mask in crowds versus the unconscious risks of getting sleepy behind the wheel.