As caloso posted, even hitting 30 mph requires a rider to be able to put out about 6-700W for any decent-sized cyclist. That's about one horsepower. And you have to get yourself up to that speed from, say, 18 mph. So you have to put out one horsepower or so for a good while - 20-30 seconds, probably.

30 mph is NOT something cyclists can easily hit, despite rampant braggadocio.

Sustaining 30 mph or even faster for any decent length of time is even harder.

Yeah, a lot of people go faster. Downhill or downwind, usually. Even just a 5 mph/8 kph tailwind reduces the power needed to go 30 mph from 6-700W down to 400-450W.

But on level ground? Without a tailwind? You ain't doing 30 mph for long, if at all.