> There's no fundamental reason that road vehicles couldn't exceed 200kph There sorta is. Air resistance and tyre/pavement rolling resistance get mighty expens

> There's no fundamental reason that road vehicles couldn't exceed 200kph There sorta is. Air resistance and tyre/pavement rolling resistance get mighty expensive at that sort of speed, and the need to carry along energy storage makes this even more problematic. High-speed rail vehicles amortise, over the whole train, the part of the drag that comes from the frontal area. Automobiles cannot do this. Once you've created a curve-free, very flat, grade-separated controlled access freeway for your 250kph cars, you've...got most of what you need for high-speed rail anyway. At that point you might as well just build some rails and overhead line and buy some TGV rolling stock.