Here is an explanation of the different levels of difficulty:
EASY - blue routes
Family-friendly, even with normal bicycles passable cycling track with a good road (fine layer of broken stones or asphalt and similar ceiling). The increase and the down grade are between 0 % and 5 %, on short distances up to 10 % - no continuous increase. Traffic-free or car-light traffic routes. There are no particular danger areas. If there are danger spots, then you will find a special labeling.
MEDIUM - red routes
Requires sportive bike riding skills and especially defensive driving behavior. Mountain bike equipment is recommended. The increase and the down grade are between 5 % and 12 %, on short distances up to 17 %. There appear confusing, winding sections. With traffic, which occupies the entire path, has to be expected.
The way facilities, including the road surface, drainage facilities ( for example water coil), shut-off devices (for example sensors), the safety devices and notes of danger spots, is geared exclusively for trade with tractors and trucks. Such devices may pose danger spots for cyclists in itself.
There are barrier because of management ratio as a consequence of natural phenomenon.
DIFFICULT - black routes
Demanding MTB route with many dangerous moments what exceeds the maximum slope of the red line and the track characteristics is even more diffícult. MTB equiment is mandatory. Situation adjusted driving is required.