Explanation
The bicycle node network is a relatively new bicycle network. It consists of a set of numbered signs, called nodes (knooppunten). Road sigs show the way to nearby nodes:
You will need a map showing where the nodes are in order to be able to use this. At the nodes you will find maps of the surroundings, but the scale of these maps can be quite different and at some places the maps are worn, or unreadable due to damage. So, make always sure to bring a map with you.
Coverage
The network almost has national coverage. As far as I know only part of Flevoland and Groningen are not yet covered.
Maps and route planners
Maps are available at tourist offices (as for routekaart fietsknooppunten) and ANWB offices. I recently (June 2009) bought a map showing knooppunten for the province North-Holland. This map (ANWB) is good for the node network and LF network, but it is not very accurate. Sometimes you cannot see that nodes are not attached, for instance because there is water between them and no bridge.
On internet you can find a national route planner for the node network:
Also several regional planners exist, but I selected this one because it has national coverage, which is most convenient. Also it is relatively easy to use, though in Dutch only.
You can download a free cycling map for your GPS device at http://sites.google.com/site/openfietsmap/
This map contains the bicyle nodes.
It has the form of an executable program for a PC, which installs the map in MapSource. Then you can transfer the map to your GPS device.
Experience
I recently had the possibility to test the system. It works fine. You can plan a route in a few minutes, and afterwards you rarely need a map. A good map is still necessary. Sometimes you cannot see wll which nodes are attached to each other. Also there may be obstacles, like closed roads forcing you to select another route. Many node points show a map with the surrounding nodes, which helps a lot if you forget to bring your own map.
Some people complain that you miss a lit of nice roads and that other people determine your route. That's true, but you are always free to deviate from the nodes and pick them up later on. The node network also runs through large cities like Amsterdam and Utrecht. I'm not yet very positive about them, because the signs are small, it is easy to miss them, if the signs stand at the opposite side of a crowded road.