That is how you kill people.

The design of the road, the street furniture, things like pedestrian traffic, parking, etc.. will all affect how people drive along the road.

If you just drop the speed limit people will have to actively concentrate on their speed. If you don't actively enforce the speed limit people will concentrate on driving over speed adherence.

Adding chicanes, speed bumps, etc.. will slow people down but change how people drive a roads and can introduce new hazards.

I know of roads with no deaths that added speed bumps which now kill a person each year, a road that added chicanes that immediately suffered multiple crashes per day until they were removed.

Heck traffic calming where I currently live, was perfectly safe and brilliant until a new housing estate opened. The housing estate has increased traffic which has slowed the road but the traffic calming now suffers alot of near misses and emergency breaking because of the increased traffic. The road would now be safer without it and a speed camera placed at a key point.

Road Safety isn't something you can magically solve by dropping the speed limit or just adding chicanes. You need to think about alot.