Signal system N

The signal system N is a railway signal that has been used by Swiss railway companies since 1986 . It replaces the old L signaling system on many routes . N stands for numerical speed signaling.

The signal system N is a stationary system and is located to the left of the track in the direction of travel . On single-lane lines or for the rightmost track of a multi-lane line, they can also be set up on the right for better visibility.

Preliminary considerations

The Swiss Federal Railways (SBB) have been developing a new signaling system since 1981 . The basic idea was the signaling of the allowed speed by means of luminous digits instead combinations of colored light points as in the previous system L (signaling velocity through L maybe points) for the existing system; analogously, were m echanical signals as system M , respectively.

The old system had the following shortcomings:

• It was no longer sensible to expand it by further speed levels.
• Illogically structured signal terms (e.g .: 1 green light = maximum speed, 2 green lights = 60 km / h, 3 green lights = 90 km / h).
• Individual points of light can be covered and thus a higher term can be simulated.
• Complex monitoring of whether all light points belonging to a signal image are actually lit.

Psychological principles

The Psychological Institute of the University of Bern has developed an expertise on behalf of the SBB. An ideal signal system should be built according to the following principles:

Control uniqueness

Clear distinction between internal control ( duty schedule and route knowledge ) or external control (deviation from the drive to internal control). In the case of system N , a single green point of light means driving to internal control , in other cases the engine driver is shown the speed directly (external control). In the case of system L , this principle was watered down because driving terms 2 and 3 could be assigned different speeds in the duty timetable.

Emphasis on competence

The capacity of the engine driver must be respected by relying in a limited area of expertise really to humans. This comes into play when driving to internal control. The speeds specified in the duty timetable are not displayed on the signal.

Actuality

Signals should be placed where the action determined by the signal should take place. In system N , the speed threshold was therefore moved from the first switch to the entry signal . Nevertheless, this principle can not be fully implemented because z. B. distant signal distances are designed for the braking distance to a standstill and therefore braking is not initiated at the distant signal when speed is reduced .

Information conciseness

Concentration of the signaling on a single piece of information that is as simple and clear as possible . This includes the clear separation of the signaling for indoor and outdoor control and the waiver of two speed indications at the same location.

implementation

Stop , warning and free travel are each indicated by a single red, orange or green lamp. These three lights are combined in a compact unit that can be aligned as a whole (in the extreme case of the L system , 12 lights per location had to be aligned individually).

To display the digits and additional symbols, halogen lamps are used, the light of which is guided by a bundle of light guides to appropriately arranged light points.

The displayed number meant either (together with a green light) the speed from this signal or (together with an orange light) the speed allowed from the next signal. Only one speed is displayed at a time, namely the lower one (with the corresponding light point - at the same speed with the green one). As a result, a speed announcement may be followed by another speed announcement and the speed execution is not displayed.

Top speed		Signal aspect at signal 1	comment
Signal 1	Signal 2
60	40		Speed ​​from signal 2 is lower than speed from signal 1: Signal 1 shows speed announcement .
40	60		Speed ​​from signal 2 is higher than the speed from signal 1: Signal 1 shows speed execution .
40	40		Speed ​​from signal 2 is equal to the speed from signal 1: Signal 1 shows speed execution .

Web link

• Signals of the Swiss Railways ( Memento of July 6, 2011 in the Internet Archive ) (DOC; 8.7 MB)