It seems to me that both travel time and accidents are measured in human life minutes, and so if you count time spent driving as not living (or just half-living) then you could determine the speed limits that lead to most time spent alive, without bringing in any equivalence between human lives and dollars.

There are a couple of confounding factors, though. In the US, speed limits were briefly at 55 mph, which was a terrible idea, and increasing the speed limits to 65-75 mph resulted in no significant change in traffic fatalities, mostly because they didn't... (read more)