Sharopoyezd – Soviet high-speed monorail project from 1930s

Very little known engineering project from early Soviet era -- https://en.wikipedia.org/wiki/Sharopoyezd. Lead by Nikolai Yarmolchuk.

Theoretically, train speeds could achieve 300km/h. Built prototype has been tested only at 70 km/h.

Project was canceled due to high construction and operating costs. There were attempts by Yarmolchuk to revive the project in 50-60s. Although, as well unsuccessful.

It's monorail meets bobsled (or a one-wheeled hoverboard) in a terrifying combination!

It's clear from the video that this would never be rideable, much less safe. A bit of debris landing on the track could cause a spectacular accident with cars and passengers launched into the air. Just look at how it wobbles around corners and even on straight lines. And that switch. What could go wrong?