300 kph is 186 mph, which is well beyond the posted speed limit of any jurisdiction I can think of. For reference, here in California, a conviction for driving over 160 kph (100 mph) is punishable as a felony, meaning at least one year in state prison. The highest speed limit in California is 113 kph (75 mph).

In metric units, a triple digit speed (eg 100 kph) is the domain of motorways (aka freeways or expressways). And even arrow-straight motorways have a maximum posted speed limit of some 140 kph. In Germany, the motorway can sometimes have no limit, but the recommended speed – the yellow speed limits in the USA – for German autobahns is 130 kph, with some speedy cars occasionally doing 200 kph, I’ve heard.

For further reference, the fastest speed achieved during an F1 motor race is 372 kph. Also, Japanese bullet trains heading west from Tokyo on the Tokaido Shinkansen route run at 285 kph.

300 kph on a public road is grossly irresponsible, since even with no one around, the road is not designed for that speed. Compare race tracks with freeways, and it becomes clear that surface quality, drainage, sight lines, clear space, and other requirements for 200+ kph just aren’t present on public roads, with the notable exception of very special public roads like the Nürburgring.