What i consider a good thing is that distances are shown in kilometers, rather then hours. Mountain trails might sometimes be marked in hours, as the hilly terrain adds it's time toll significantly, but for the most part, it is kilometers, which means that can very easily estimate how long it will take you to your destination while walking/running/biking...
But not all signage is great that in CZ. For example driving roads are mostly marked by "destination cities" at intersections rather then by road numbers (except of highway exits), so when planning a road trip, you must create an itinerary of towns to pass through, rather then simply following a map of roads.
In my experience, distance is the norm. I'm not sure I've ever seen a hiking/walking trail marked for difficulty/time rather than distance. (Of course a trail map/book/description may include more information including a range of time to complete.)
Ski trails of course are usually just marked for difficulty level. (Which is mostly relative to other trails on the same mountain.)
Interesting. "Book time" is a useful idea. The issue is that you need to have a good baseline for how you personally compare to the book time. It works well on an individual basis with a regional guidebook. I'm less sure what to make of it in a sign in an unfamiliar area. (I have seen it in Japan as well. I usually take it as something of an upper limit.)
IIRC almost all the signs in the swiss alps are time, not distance. Which makes sense given how steep many of them are -- even if it's not your pace, it's a quick summary of distance + elevation. Perhaps this is less needed in Czech terrain.
They are also coloured by difficulty, not length -- yellow will be a big wide road, red a mountain path, blue may expect you to have brought crampons.
But not all signage is great that in CZ. For example driving roads are mostly marked by "destination cities" at intersections rather then by road numbers (except of highway exits), so when planning a road trip, you must create an itinerary of towns to pass through, rather then simply following a map of roads.