It is a really superb and effective system. The Dutch ones have 'mushroom' like posts at the node junctions with distances to numbered nodes on the various faces.
Some people still preferred antequated bits of paper with squiggles and silly random colours all over them ...
Having tried to navigate solely by the node numbers on a few rides in the countryside around Amsterdam, it works really well until you can't find one of the numbers along your route. It's not too bad if you have a map with you showing the other node numbers, but if, like me, you only had a list of the nodes along your intended route , you're reduced to circling random nodes until you find one with a map board
This reminds me of a truly disastrous long distance bushwalk I started in western australia, with my then new (and now ex) wife. We were very young, I was experienced in bushwalking. I was very worried about the lack of maps. She was enthused by the description - walk along the trail to the next yellow dot on a tree. How hard could it be?
Since the trail was lined with trees every 2ft, I expected finding the yellow dots every 10 miles or so (or 30 miles in some cases) could be difficult. What I didn't know was that some locals thought it amusing to remove the dots.
On the second morning we'd walked some hours along an easy to follow dirt track. Which had taken a right hand turn. We should have been going straight on. No yellow dot. 2 hours of searching. No trail to the left (straightish on). No yellow dot. No fresh water for 20 miles apart from on the (absent) yellow-dotted trail, unless we backtracked and jinked 7miles to what passed for a main road and tried hitchhiking.
I was getting very, very uneasy by this point and extremely reluctant to carry on with the whole idea. I knew the risks of getting lost, we didn't have decent maps, and at the very start the damn dots were missing. Massive row ensued, we backtracked, I ended up carrying both rucksacks the 7 miles and very nearly divorced about 3 weeks into the marriage.
It turned out to have been a good call. Local Forestry department confirmed that the dots were missing all over the trail and it was almost impossible to follow - unmarked, not walked, no footfall. I'm told it's easy to follow now and people use GPS just in case anyway. wimps.