Epic fail

Drivers don't go slower. They never do, unless you put silly speedbumps in the way. Like with the road narrowings, they just make driving and cycling more dangerous.
...

...Many people are like this, I doubt anything will change it. People are quite stupid in many different ways.

This isn't 100% true unless you're talking about the tiny minority of psychopaths. The fact that there's no barrier DOES make drivers much more aware and somewhat more careful.