Cultural diferences
Denmark and the Netherlands do not differ significantly when it comes to biking regulations. It is mandatory for both to follow the traffic signals, drive on the right side of the road, and give an indication to other vehicles while turning.
When it comes to following the rules, however, cyclists in the two European countries have their own customs. Even though helmets are not compulsory in either country, it is common to see bikers using it in Denmark, while it is mildly ridiculed in the Netherlands.
Danes are more disciplined in following traffic rules, and would stop when the traffic signal is red, even if no vehicles are in sight. The Dutch on the other hand would not consider the rules as set in stone, and follow it only when they deem them appropriate.