It's what you get from the game going fully exponential while the car has the higher speed than anything it deserves. Me, I'd have gone with 40, 60, 80, 120, 160, 240, 320 as speeds, so basically rounded up to 50 kph, 75, 100, 150, 200, 300, 400. Those are running rates so -2 penalties to vehicle tess apply. That'd put a supersonic airplane at speed 11. And you wouldn't have a speed 3 car being unable to handle the highways, since they'd be at 100 kph (still slower than the 120 limit) rather than 50. And a speed 4 would actually be able to reach that legal speed limit of 120 thanks to a max of 150 kph, rather than being stuck under it at 100 kph.