This criterium is about protecting cyclists from wind and rain.
A huge decrease of more than 50% in CH usage can often be seen at rainy days (often the same days as traffic jam lengths are the longest). Since CH are the backbone of the cycling network, it highly recommendable to provide a minimum of sheltering on the backbone so that cyclist can always and at any time rely on the same infrastructure. At the Cycle Highway Industry meetings some new forms of sheltering were designed.
To measure this criterium you count the amount of shelters from rain and wind per section (f.e. under bridges or specific cabins or Bike HUBs). To obtain level 3 you need at least 10 shelters per 10km.
For LEVEL 4 more than 50% of the Cycle Highway needs to be semi-covered.
Example: sheltering by extending an existing (transparent) sound damping wall or using an existing infrastructure under a railway in Berlin.