Danish Signaling, Protection Signals

by Carsten S. Lundsten

Updated 010131 - history document here

Introduction
Protection Signal Types
Protection Signal Aspects and Indications
     "Stop" (Danish: "Stop")
     "Proceed" (Danish: "Kør")
Protection Signal Useage
     Spurs on the Line
     Movable Bridges
Peculiarities

Introduction

Protection signals (Danish: DækningsSignaler) is the name for signals protecting spurs and movable bridges on the open line. Protection Signals are only used where there is no block system on the line, and are very rare. True Protection Signals only exist at 3 locations today. If the stations feature Exit Signals , the Exit Signals may instead act as Protection Signals as well.

On lines with block systems, the block system includes the protection of the spur or bridge. On these lines either the Automatic Block Signals or the Exit Signals also work as Protection Signals. Examples of this are included in the Usage chapter , though only true Protection Signals are covered in the remaining text. Combined Automatic Block and Protection Signals show no physical difference from pure Automatic Block Signals, except for the naming.

Protection Signal Types

Protection Signals are 2-lamp signals only capable of displaying "Stop" and "Proceed": Some signals feature a high background plate, often originating as a station Entry Signal which has since been converted into a Protection Signal:

Protection Signal Aspects and Indications

"Stop" (Danish: "Stop")


Stop	X	X

"Proceed" (Danish: "Kør")


Proceed at prescribed speed	X	X
The signal does not convey information about indication on the following Main Signal	X	X
Trains with active Cab Signal: Cab signal will govern	X	X

Protection Signal Usage

Spurs on the line

Without Line Block System

On lines without an automatic block system, Protection Signals are used to protect spurs on the line. Currently only two such signals are in operation, both located on double track. The Protection Signal is located in approach to the spur, advance signaled by a Distant Signal. Marking the spur for trains running on wrong main is a Station Without Main Signal Sign, located 800m in approach to the spur.

The Protection Signal is normally at "Proceed", being reset to "Stop" when the switch to the spur is released:

With Line Block System

On lines with an automatic block system, an Automatic Block Signal takes over the role of the Protection Signal. Where the spur is in the first block section, the station Exit Signal acts as a Protection Signal:

A combined Automatic Block and Protection Signal is called such (Danish: Automatisk Mellemblok og Dæknings Signal), whereas an Exit Signal doesn't receive the additional naming. The reason for this is not clear, but it is likely a matter of tradition. Most double track Automatic Block and Protection Signals act as normal Automatic Block Signals, i.e. they normally display dimmed "Proceed"/"Proceed Through", with the switch to the spur locked.

To enter the spur, the switches must be released by a neighboring station. The switch release sets the Automatic Block and Protection Signal to "Stop", and the switcher must pass the signal at "Stop" after special permission:

Wrong Main Exit and Wrong Main Block Signals act as Protection Signals for the opposing direction in a similar way.

The only installation of an Automatic Block and Protection Signal on a bidirectional line has the signal showing "Stop" as its normal aspect, clearing when the neighboring station clears its Exit Signal. The switch can be released either before the train gets so close as to see the the protection signal is clear or after the train has entered the block. In the latter case a timer delays the release of the switch until the train has either stopped or has passed the spur.

Movable Bridges

Without Line Block System

There is only a single movable bridge (Oddesundbroen) in Denmark on a line without a block system. The bridge has protection signals from both sides and is interlocked with the signals. A Dwarf Signal close to the movable bridge span informs of the status of the span, so that a train even with a failure of a Protection Signal can directly observe the status of the span:

With Line Block System

The other 3 movable rail bridges in Denmark are all located on single track with an automatic block system. Consistent with usual Danish practise, these lines have no intermediate Automatic Block Signals. The station Exit Signals also protect the bridges, and the bridges are interlocked into the block system. A Dwarf Signal on each side of the movable bridge span reflects the actual status of the span at any time :