Canada

This is the only correct answer here. You want drivers to slow down? Stop building big, wide, straight roads. You need to add curves with trees and barriers, narrow the lanes, and (gasp!) even remove some lanes. Everything else is theatre.

The stats from the city of Ottawa show that drivers slow down when speed regulations are enforced.

I fully support improving roads to make them safer. In the meantime, enforcement of existing rules seems like a low cost alternative.

Problem is people aren't good judges of what is, in fact, a safe speed.

Edit: the second problem is that making it feel unsafe while not being unsafe (or unfeasible to maintain or prohibitively costly) leaves very few options.