National Road network (Netherlands)
Nationale Wegen (National Highways) or simply N-wegen (N-roads), was a numbering system for a set of main highway routes in the Netherlands, used from 1957 through 1976. In 1957, signposted road numbering was introduced in the Netherlands and the governments Rijkswegen plan foresaw in an increasing number of highways, together forming a nationwide system.
Source: Wikipedia — National Road network (Netherlands) (CC BY-SA 4.0)