Wrong Way Signs

I was thinking about crashes that happen when people enter the highway via an exit ramp and end up going head-on towards oncoming traffic.  Part of the problem is limited signage, so how about painting a series of signs on exit ramps asphalt, say 15-20 feet apart, something like this first image that repeatedly tells you're going the wrong way?

Now if you're properly leaving the highway, you see these signs, pointing the correct way but with the letters upside down and not spelling anything identifiable, not (I hope) causing any confusion.