[ZenGum]

In (South) Australia, we have the same set up for the same purpose. A small black post with a red cross (Christian shape) marks a fatality, and a white post with a red cross (I think) marks a serious injury.

The idea is, I guess, to remind drivers about the imminence and immanence of death, and alert them to particularly dodgy corners. I've no idea if it actually works, or if it is just distracting.