Well it depends. Technically speaking, it’s around twice as fast as standard speed on highway (at least in France, so 130kmh). In terms of feelings, it’s probably not that faster? I never went above 140 or so but from my experience, your brain adapts to the speed, so if you got to 300 not that suddenly it probably does not feel like twice as fast than the usual. In terms of safety, it may be more than twice the danger. I’m no expert, but depending on the vehicle and how many other vehicles there are on the highway, it could be very dangerous.