OpenStreetMap
The 'insulindeweg' http://www.openstreetmap.org/?lat=52.361195&lon=4.934189&zoom=18&layers=M is similar on the left and right parts. But on the left, the cycleways have been drawn separately, while on the right, they are mapped with 'cycleway=track' and similar attributes.
Easier to edit, but not so good with relations, turn restrictions etc.
Is there a preferred way to do this, depending on situation?
Discussion
Comment from Pieren on 17 January 2012 at 12:50
It is not depending on situations. The best is to draw a separate line (see http://wiki.openstreetmap.org/wiki/Bicycle) but some people do not know the exact position of the track (e.g. when surveying from a car). If you have a better source (GPS on the cycle track or aerial imagery), then you would be better tracing it as a separate line (as you can notice, it is more clear and easier to tag)
Pieren