Greek railway signalling
On lines currently operated by the Hellenic Railways Organisation (OSE), signalling was not installed until World War II. There were few trains running and all traffic control was performed by the station masters (Greek: Σταθμάρχης). They controlled trains by hand signals and whistles and also delivered written orders to the train drivers for special operating procedures. Station managers were coordinated by morse-code landline telegraph and, later, by telephone.
The first semaphore signals were installed by the German military occupation forces during World War II and are almost identical to the "H/V" signalling system of the Deutsche Reichsbahn of the same period. Main signals consisted of two arm semaphores and distant signals of yellow disks. These signals controlled the entrance to stations and were operated mechanically by wire from the station platform. Usually on each direction there was one semaphore controlling the entrance to the station, preceded by a distant signal. Some of them still survive, but they are no longer operational.
Local signalling using two aspect colour light signals controlled by the station manager was installed at some busy stations like Athens/Larissis Station, Athens/Peloponnese station, Inoi junction etc.
All aspects of railways signalling are described in the current version of document "Γενικός Κανονισμός Κυκλοφορίας - Μέρος Α - Κανονισμός Σημάτων και Παραρτήματα I, II, III, IV, V & VI". This is a collection of different regulations, the main part covering semaphore signals and lineside signs, with appendices covering new signalling systems. It was issued in electronic format by Hellenic Railways Organisation in 2009.  The contents of this document include:
- Main body: Traditional signs and signals, reflecting signalling and operating practices as they were around 1970.
- Appendix I: Colour light signalling in Thessaloniki Railway Complex (New Passenger Station and Shunting Yard).
- Appendix II: Colour light signalling system initially installed in Thessaloniki-Platy and Athens-Inoi sections.
- Appendix III: Current colour light signalling system and procedures.
- Appendix IV: Special local signalling systems in Edessa Station and at Kalamata Engine Shed junction.
- Appendix V: Level crossing signalling system (Greek: ΑΣΙΔ).
- Appendix VI: Recently introduced signs for electrified lines.
Semaphore signals followed the German pattern and consisted only of home signals (German: Einfahrsignal) with the corresponding distant signals, covering the entrance to stations and are described in Chapter II of the Signalling Regulation. There were no starting semaphore signals (German: Ausfahrsignale), as the trains were signalled out by the Station Master in person, holding up a staff with a green disk and blowing his whistle. This practice was followed when colour light signals were first installed in the sections Athens - Inoi Junction and Thessaloniki - Platy, even though the new system included starting signals, but it was abandoned later, with the introduction of the current signalling system.
Around 1973, as a result of a serious train accident that took place between Doxaras and Orfana stations in Thessaly, the Hellenic Railways Organisation installed VHF/FM radios on all stations and driving cabs. In many cases the orders are transmitted over the radio by station masters, instead of being handed out in printed form. In the past OSE used ten different VHF frequencies. An allocation of 150.05 to 151.6 is reserved for the VHF/FM service. Today operations use four channels as follows:
|1||150.290||Simplex||Peloponnese network and Ormenio - Thessaloniki - Amyntaio - Florina - Kozani|
|2||150.310||Simplex||Piraeus - Thessaloniki - Eidomeni mainline|
|3||150.330||Simplex||Locomotive and train depots|
The suburban section from Acharnai Railway Center to the Athens International Airport station uses commercial TETRA radio instead of VHF/FM.
Currently the VHF/FM system is being phased out and replaced with a digital communications network based on the GSM-R technology which shall also carry ETCS-Level 1 cab signalling. The GSM-R system was designed by an engineering consortium (DeConsult-Lahmeyer-TRADEMCO) and is implemented by Siemens. Frequency bands 876-880 MHz and 921-925 MHz have been specifically reserved for the GSM-R/ETCS service. 
In recent years the Hellenic Railways Organisation undertook modernisation of the section from Piraeus to Thessaloniki and Idomeni. This line is using block signalling with centralized control from a small number of signal boxes (Appendix III of Signalling Regulation). Signals are four aspect colour light signals, which are described in the following table. Of course some signals have only three or two aspects when there is no need for all possible indications (for example if the signals are not followed by points). There are even a few single aspect signals, displaying either steady of flashing amber (ΦΠ-10 and ΦΠ-12). Currently the colour light signalling is functional on the following sections:
- Acharnai Railway Center to Inoi junction. (Appendix II, converted to Appendix III)
- Inoi junction to Tithorea (Appendix III)
- The single line mountain section from Tithorea to Domokos. It is the first section of the OSE network with full modern signalling and control from a central signal box located at Leianokladi (1982). (Appendix III)
- Domokos to Platy (signal box located at Larissa) (Appendix III)
- Platy to Thessaloniki, up to signal box TX1 (Appendix II, converted to Appendix III)
- Thessaloniki complex, controlled from five signal boxes (TX1 to TX5)
- Thessaloniki to Idomeni (Appendix III)
- Ano Liossia to Kiato (Appendix III)
- Acharnai Railway Center to Athens International Airport (Appendix III)
On the following sections the installation of signalling is at an advanced stage:
- Piraeus to Acharnai Railway Center, with the exception of Athens Central (Larissis) station.
- Inoi junction to Chalkis
- Acharnai Railway Center to Ano Liossia
Slightly different signalling systems were originally specified for the sections Athens - Inoi Junction and Platy - Thessaloniki, which are described in Appendix II of the Signalling Regulation.
Specialized local signalling systems exist at:
- Junction of Kalamata Engine Sheds (Appendix IV)
- Edessa station (Appendix IV)
- Thessaloniki Railway Complex (controlled from five signal boxes TX1-TX5)
The following table describes the modern (Appendix III) signalling system.
|Signal||OSE Code||Meaning||Next signal||Notes|
|ΦΠ 1||Proceed||ΦΠ 1||Proceed with maximum speed for section, unless it is restricted by other signals.|
|ΦΠ 2||Slow||ΦΠ 1||Proceed with a maximum speed of 40 km/h from the signal to the exit of points area.
Usually indicates that the train enters a diverging line at a junction or the secondary
line of a passing loop.
|ΦΠ 10||Caution||ΦΠ 0||Reduce speed to stop at the next signal.|
|ΦΠ 12||Caution||ΦΠ 2
|Reduce speed to proceed with low speed after next signal.|
Stop at next signal
|ΦΠ 0||Proceed with a maximum speed of 40 km/h from the signal to the exit of points area.
Next colour light signal is red. Usually indicates that the train enters a passing loop
while the starting signal at the other end of the loop displays a red aspect.
Signals are tagged with an identity which consists of a three or four letter code denoting the station and a number (for example "OIN 3"). Distant signals share the same number with the corresponding main signal with the addition of letter "A" in front of the number (for example "OIN A3").
Most switch points, especially those located in stations and marshaling yards, are equipped with a position indicator, (Signal 31) which is directly connected to the points operation mechanism. When the points are set to the through track, it displays an orange rectangle to the facing-point movements and a white rectangle to trailing-point movements. When the points are set to the diverging route, the indicator displays a diagonal arrow to the facing-point movements and a white circle to the trailing-point movements.
Athens-Piraeus Railway, the predecessor of Athens-Piraeus Electric Railways, installed a signalling and points control system in 1900-1904, during the electrification of the line. The mechanical signalling system was designed by Siemens & Halske and used semaphores for the main signals and square boards for the distant signals. Most semaphores had one arm, whilst a small number, which were followed by points, had two arms.
The line between Piraeus and Omonoia Square was divided in six blocks. Details of the design and operation of the signals, the points and the interlocking survive in Section D of the contract between the Greek Government and the railway company. The system became operational in 1904.
In 1924 the new company "Hellenic Electric Railways" signed a new contract with Siemens & Halske to renovate the signalling system. The semaphores were replaced with colour light signals and electrical interlocking. In the early 1950s colour light signalling was installed in the extension from Omonoia station to Kifissia station.
Most signals are "main signals" with two aspects (red and green). There are also a few two aspect (yellow and green) distant signals, in locations where the main signal is not visible from a reasonable distance. If the points at a junction are set to a diverging route, this is indicated by a special "junction signal", a white diagonal line on black background. Junction signals are usually colocated with main signals, although there are quite a few stand-alone ones.
Main signals and junction signals are tagged with a number identity. Distant signals are tagged with the same number as the corresponding main signal, preceded by "Vs" (German: Vorsignal).
A new modernization programme began in 1982, still using mainly two aspect colour light signals. Gradually the signalling system was adapted to central control from a power signal box next to Eirini station. The line circuits operate with audio frequency alternating current (Siemens FTGS 17). In 1983 ISAP installed an electomagnetic Indusi cab signalling system, which was supplemented after 2003 with an Automatic Train Protection (ATP) system.
A VHF/FM simplex radio system was installed in stations and driving cabs in 1985, which operated on 161.325 and 161.375 MHz. It was replaced with a UHF/FM repeater operating on 418.575 MHz in 2004. This system was supplemented with a TETRA system in 2004. However radio is rarely used for train control under normal operating conditions.
Athens Metro signalling
Signalling on the two lines of Athens Metro is centered on an Automatic Train Protection (ATP) system, type LZB 700, compatible with the ISAP ATP system. An Automatic Train Operation (ATO) system has also been installed and is under evaluation. In the short section between Larissa station and Sepolia Depot an Indusi system was installed initially, so that the section could be used by ISAP trains, however this was later removed. The network is controlled by operators stationed in a central signal box located at Syntagma station.
Points are protected by two aspect color light signals, designated as "switch point indicators". These signals display either a white or a red light.
Signals are tagged with an identity which consists of a three letter code denoting the station and a number (for example "ΣΥΝ 11").
Athens Tram signalling
At level crossings Athens Tram uses special light signals which are coordinated with road traffic lights. The signals are quite different from regular rail signals, in order to avoid confusion with adjacent road traffic lights. At some locations green wave signalling has been established, giving priority to approaching trams over road vehicles.
- "General Rail Traffic Regulation - Part A- Signals Regulation and Appendices I, II, III, IV, V & VI" (Greek: Γενικός Κανονισμός Κυκλοφορίας - Μέρος Α - Κανονισμός Σημάτων και Παραρτήματα I, II, III, IV, V & VI) , Hellenic Railways Organisation, electronic edition (2009).
- National Frequency Allocation Tables, Ministerial Decision 17225/655, 10 March 2006, Government Gazette Issue B'399/2006, page 4904.
- National Frequency Allocation Tables, Ministerial Decision 17225/655, 10 March 2006, Government Gazette Issue B'399/2006, pages 4911-4912.
- G. Nathenas, A. Kourbelis, T. Vlastos, S. Kourouzidis, V. Katsareas, P. Karamanis, A. Klonos, N. Kokkinos (2007). Από τα Παμφορεία στο Μετρό (in greek) 2. Athens: Μίλητος (Militos). pp. 574–576. ISBN 978-960-8460-91-1.
- 130 Χρόνια Ηλεκτρικοί Σιδηρόδρομοι Αθηνών-Πειραιώς Α.Ε. (130 years of Athens-Piraeus electric railways). ISAP. 1999-2005. pp. 58,63,99–105. ISBN 960-86477-0-3.
- 130 Χρόνια Ηλεκτρικοί Σιδηρόδρομοι Αθηνών-Πειραιώς Α.Ε. (130 years of Athens-Piraeus electric railways). ISAP. 1999-2005. p. 59. ISBN 960-86477-0-3.
- G. Nathenas, A. Kourbelis, T. Vlastos, S. Kourouzidis, V. Katsareas, P. Karamanis, A. Klonos, N. Kokkinos (2007). Από τα Παμφορεία στο Μετρό (in greek) 2. Athens: Μίλητος (Militos). p. 636. ISBN 978-960-8460-91-1.
- G. Nathenas, A. Kourbelis, T. Vlastos, S. Kourouzidis, V. Katsareas, P. Karamanis, A. Klonos, N. Kokkinos (2007). Από τα Παμφορεία στο Μετρό (in greek) 2. Athens: Μίλητος (Militos). p. 637. ISBN 978-960-8460-91-1.
- G. Nathenas, A. Kourbelis, T. Vlastos, S. Kourouzidis, V. Katsareas, P. Karamanis, A. Klonos, N. Kokkinos (2007). Από τα Παμφορεία στο Μετρό (in greek) 2. Athens: Μίλητος (Militos). p. 709. ISBN 978-960-8460-91-1.
- G. Nathenas, A. Kourbelis, T. Vlastos, S. Kourouzidis, V. Katsareas, P. Karamanis, A. Klonos, N. Kokkinos (2007). Από τα Παμφορεία στο Μετρό (in greek) 2. Athens: Μίλητος (Militos). p. 710. ISBN 978-960-8460-91-1.
- Γ. Καλογιάννης (2006). "Ηλεκτρονικά συστήματα τηλεματικής, ελέγχου και ασφαλείας Τράμ". Ηλεκτροκίνητα μέσα μεταφοράς στην Ελλάδα - Υφιστάμενη κατάσταση και προοπτικές (in Greek). Technical Chamber of Greece. Retrieved 2010-09-23.
- Media related to Railway signals in Greece at Wikimedia Commons
- Athens Metro signalling systems
- Athens Metro communication systems