Would it work for speed limits to be "informational" only instead of forced on everyone?

I was in some country, don't remember which, and they simply had signs that said something like, "road suitable for speeds up to x km/h for cars" - something like that. Like, if you knew you were in a Porsche and knew perfectly well you could go 50 mph faster, then go for it. And, if you were in a tractor trailer or some kind of top heavy vehicle, then you would know to go slower. Another sign said something like "turn ahead unsuitable for vehicles with wheel base more than x meters" Not "NO TRUCKS" or whatever. What do you think? Could we manage not to kill ourselves if speed limits became "informational" only? Do some people need to be told not to drive so fast that they jump the road?