WTF? Spoken like an inveterate speeder... it's at best equally dangerous, the effect you are speaking of happens for both higher and lower speeds. At low speeds, other cars pass you. At high speeds, you pass other cars. Either way, every pass is an opportunity for failure, and the probability is higher the higher the relative speed. However, the road, barriers, trees, etc, is always going at 0 mph, so not just the relative, but also absolute speed control crash severity. Twice the speed means 4 times the kinetic energy... speed kills.