I would have to say the shoulder. They are very small on some highways with barely enough room to pull off. If you have to change a tire on the driver's side of a vehicle, the traffic can be so close as to give off wind shear which can make the vehicle having the tire changed shake enough to actually move a little. The person changing the tire can also be hit because the cars approaching may not see you in time or may swerve and hit you.
I would say wherever it floods , is slick , hydroplanes those are some dangerous areas
I would say where there are Ice storms or black ice which are unfor see able icy spots on the road and drivers are driving like it is a perfect day and it seems they don't get injured but cause other accidents where people either end up dead or hurt very badly.....I hope this is what you are asking, if not a dangerous spot to me is the side of the highway if you have car trouble or flat tire and have to pull to the side and there never seems to be enough room,usually I'm afraid to stay in the car and afraid to get out it is awful...