This criterium is about the specific branding and identity that is f.i. integrated in signposts along the cycle highway or in other (online) touchpoints. It deals with the brand awareness of your cycle highway, from the perspective of non-users or potential users. The highest level is achieved when there is a national or even better an European identity for cycle highways.
COHERENCE - Awareness
The F3 cycle highway between Leuven and Brussels uses a network-identity on the level of Flanders (5 provinces). 
Standardization with C-numbers can help to create diverse economies of scale. 
Comparison between the branding strategy behind the F-network (5 provinces of Flanders) and the RS1 cycle highway... 
The Rijnwaalpad and its unique logo is an example of route identity (level 2). If this logo is systematically combined...
For LEVEL-1 the cycle highway doesn't have a name or identity. A local identity corresponds to LEVEL-2, f.i. Rijnwaalpad between Arhnem and Nijmegen or the HST-route between Leuven and Brussels.
When the local name or identity is combined with (or replaced by) a broader network-brand for the different cycle highways in the region you achieve LEVEL-3. See f.i. the network-identity with C-numbers that is established in London and the region of Copenhagen. Another example on a higher scale is the F-network of the five provinces of Flanders. The Rijnwaalpad and HST-route were opgraded to level 3 (F325 and F3).
For LEVEL-4 it has been agreed to use C-numbers at European level for the indication of a cycle highway. Browse the CHIPS recommended identity-strategy in the readability toolbox for more details and arguments.
An optimal readability is achieved when the awareness aspect of readability is combined with the infrastructural aspect of readability.