Grunnsignal

Grunnsignal, meaning "base signal" in Norwegian and related Scandinavian languages, is a term used in railway signaling to denote a fundamental signal that forms the foundation of the signaling hierarchy. It represents the lowest-level permission status that controls whether a train may enter or proceed into the next section of track. In many systems, the grunnsignal operates in conjunction with higher-order signals that specify routes, speeds, or additional restrictions.

In practice, grunnsignal can take various physical forms depending on the era and country. In older networks it may have been a semaphore arm or a disc, while modern installations typically use color-light signals. The exact meaning of its aspect depends on the national rules; generally, a permissive aspect allows movement into the next block or into a set of tracks, whereas a restrictive or stop aspect prevents further movement. A grunnsignal is often a prerequisite for clearing subsequent signals or route indicators, meaning that a driver must observe the grunnsignal before a more specific aspect can be shown.

The term is most commonly encountered in Norway and Sweden, where it appears in historical and contemporary signaling literature. While many networks have adopted newer signal families and centralized control, the grunnsignal concept remains part of the regional signaling tradition and is referenced in discussions of the evolution of railway safety systems.