[hyrix]

The way to reduce speeds is not to make the road more dangerous but rather to signal the expected speed correctly. The article a sibling commenter linked makes this point:

> [...] The premise is simple: drivers will make occasional mistakes—veer a bit out of their lane, fail to brake hard enough, etc.—-and if the street is wide, with high visibility in all directions, and free of immediate obstacles such as trees and fences, those mistakes won’t be catastrophic. The problem: this street feels too forgiving to a driver. Too safe and comfortable. So drivers speed up. The engineers didn’t account for this aspect of human psychology.

Drivers behave as expected when they can't see around obstacles, the lane feels tight, and there are curves and other features that reduce visibility. These roads aren't inherently more dangerous, they just give drivers less margin for taking excessive risks.