Holland is safe it's civilized. But if you neglect your own health or safety, you probably can't sue anybody for your mistake.
You have to watch out for yourself.
Low cast-iron fences bordering a sidewalk might be topped with decorative spikes.
If there's a hole in the sidewalk, you just have to know to not step into it.
An infrastructure project might not be protected by even a strip of tape never mind a barrier. The operators of heavy equipement are watching for you, and you must also watch for them.
Overhead work? You decide whether or not you'd like to walk underneath.
I met a Dutch girl in Ireland once. She laughed that there are so many warning signs there. I hadn't noticed I'm from America. Very little goes without warning in America. If a potential civic legal responsibility is involved and there usually is, in a litigious culture there's a sign for it.
Warning this, danger that. This kind of posting is rare in The Netherlands as is much of the protective apparati that one might expect in the case of urban dangers.
The Netherlands is a safe country. But the legal atmosphere does not require anybody to warn everybody about every danger, and it is not customary to do so.