https://en.wikipedia.org/wiki/Motor_vehicle_fatality_rate_in_U.S._by_year
Road deaths and road deaths rates have been both falling over the years. Of courser, it is nearly impossible to know exactly why.
There has been a lot of innovation around road safety over the years. if there were no incentive, there would not be innovation.
I can't speak for many, but I know our company years ago had someone form the MN DOT come talk to us around road safety and design, and they actually have a pretty good database and procedure in how they prioritize various projects.
It is usually when the politicians get in the way that problems are caused....in my opinion.
I think in some ways Europeans are ahead of us, as there is no doubt that round abouts are the safest intersections around.
I have also noticed they are starting to design on and off ramps differently with fewer lights and different traffic patterns