As for Norway always having those obstruction markers is not quite true. It's not very common to use in highway tunnels for instance.
Picture from "Rælingstunnelen", which is located
here
They are more commonly used in older tunnels (which we have a lot of) where light conditions are poor and the road is a lot more narrow. So I guess you could say they are used in low standard tunnels. The purpose of those white and black markers is to guide you through the tunnel. They do ofcourse have reflectors as with most signs. A lot of our tunnels do not have that clean surface on the wall, which may also be a reason for why the obstruction markers are used. The uneven wall surface can make dangerous situations if the driver does not pay attention to the change in width.
This is a very good example of sign usage:
https://www.youtube.com/watch?v=dngS6cTZZws
Or this:
https://www.youtube.com/watch?v=kNkJr0NibT0
Just for the record, we do have some nice tunnels in Norway as well! Take Lærdalstunnelen for instance! It's our longest tunnel, at about 25 km!
![Image](https://dracurella.files.wordpress.com/2010/08/tunnel3.jpg)