Recently I visited a historical hydro power plant, which is still operational. The operators were in the process of adding huge shields and fences around the flywheels due to safety regulations to protect visitors. Apparently they had been only fenced off by a rope and the faith in humans‘ self preservation instinct for the last 100 years. However, when i saw those fences, it struck me as very odd why this is not mandatory on every road. The amount if kinetic energy of those flywheels is certainly comparable to a 1-2 ton car moving at 30+ km/h.