It is not just about curviness though, chance of death for a hit pedestrian sharply increases after 40mph and is practically 100% at above 60mph. To be fair it is also quite high at 50mph so this is not just an issue of "if he went with 50 they certainly wouldn't die" (though they would have had better chance for sure). But this is to say, when they put these limits, they don't just pull them out of their asses to torture drivers.