But I don't share your intuition that safety is also relative in that way. If you're driving dangerously (too fast, or while drunk), you're driving dangerously, even if everyone else is driving dangerously too. If you're in a country where nobody wears a seatbelt, it's still prudent to wear a seatbelt, just as much as in a country where that is the norm. I don't think Google Maps should encourage people to drive as dangerously as everyone else. Quite the opposite!
It's fine to point out that many people are terrible drivers and that a given crash that happens is more dangerous at a higher speed and if everybody were to drive under 60 at all times we'd all be safer, but clearly that will never happen unless we install a totalitarian government, put governors on all cars and give prison time for disabling them, with enforcers stationed everywhere to monitor. But no democracy would vote for that, so I don't think it's worth spending much mental energy on such hypotheticals.
> encourage
I think just the opposite: My feature would encourage people like me, who drive a "fast car" and can occasionally accidentally go too fast if a road is especially uncongested, to slow down to the speed that is customary or that others are driving, by reminding me that I could get a ticket and that driving faster than everyone else is dangerous.