Bugatti has broken the 300mph barrier
It's futile to actually have road-legal cars that go this fast because you can't do very much useful with the speed.This is much too fast for the human operator (driver) to safely react to things outside the cockpit, which is why for example Britain owns trains capable of 140mph in service but deliberately limits them to 125mph. Tests suggested drivers couldn't be relied on to reliably observe and react to a lineside signal (showing e.g. double amber, "Prepare to find the next signal at: Prepare to find the next signal at: Danger") passed at 140mph. The "obvious" upgrade is to put the signals inside the cab with the driver, and that's how high speed trains work. But a car doesn't have in-cab signals either, and it has a LOT more external signals to respond to, including several signs we see in that video.