It's impractical and patently unsafe to demand some sort of limiter or governor installed that restricts a vehicle's top speed to 60 mph so long as a human being is required to control the vehicle.  The reason has mostly to do with the surplus of power required to safely accelerate and merge with faster-flowing traffic, especially here on Oahu with its many short onramps (as compared to the mainland).  Indeed, it's often the case too, that a driver may have to quickly accelerate beyond the posted speed limit to AVOID a collision.  I speak from much personal experience.