
English: 
Hi railway lovers. Welcome to Railways explained.
Today’s topic is rail signaling and its evolution through different periods of time since the beginnings of railways.
As you know railways have a complex system.
It includes several technologies working together with aim to fulfill demands in terms of capacity speed and mobility.
So, the railways can be divided into different systems and subsystems depending on their functionality.
One of those systems is of course, the signaling system. This video is an attempt to explain in a simple way
how did railway signaling evolved through different periods of development of railways and how it really works,
so everybody can understand its basic concept.
Before we start with historical overview of the development of the signaling system,
we must first mention one basic operational rule on railways.

Serbian: 
Zdravo ljubitelji železnice. Dobrodošli na kanal Railways explained.
Današnja tema je železnička signalizacija i njen razvoj u različitim vremenskim periodima razvoja železnice.
Kao što znate, železnica je složen sistem.
Uključuje nekoliko različitih sistema koje rade zajedno sa ciljem da ispune zahteve u pogledu kapaciteta, brzine i kretanja.
Dakle, železnice se mogu podeliti na različite sisteme i podsisteme u zavisnosti od njihove funkcionalnosti.
Jedan od tih sistema je, naravno, sistem signalizacije. Ovaj video je pokušaj da se na jednostavan način objasni
kako se sistem železničke signalizacije razvijao kroz različite periode razvoja železnice i kako on zaista funkcioniše,
tako da svako može da razume njegov osnovni koncept.
Pre nego što započnemo sa istorijskim pregledom razvoja sistema signalizacije,
prvo moramo pomenuti jedno osnovno operativno pravilo na železnici.

English: 
Due to safety reasons on each segment of rail infrastructure,
there can be present only one train at the same time.
At the very beginning only one train could be present on the entire railway line,
which was, by the way, relatively short and mostly connecting only point A with point B.
However, as demand for rail traffic grew and therefore the need for more than one train on the line,
it was necessary to develop operational rules and systems. That would make that possible.
However, the basic premise has remained the same both for signaling of the 19th century as well as for signaling of the 21st
and that is
Trains cannot collide only if they are not permitted to occupy the same section of line at the same time.
…When peoples were signals
It was necessary to find a way for organizing operation of more than one train on the same railway line.
For that purpose, railway lines were divided into sections known as blocks.

Serbian: 
Iz bezbednosnih razloga, na svakom segmentu železničke infrastrukture
može istovremeno biti prisutan samo jedan voz.
Na samom početku, samo je jedan voz mogao biti prisutan na celoj železničkoj pruzi,
koja je, inače, bila relativno kratka i uglavnom je samo povezivala tačku A sa tačkom B.
Međutim, kako je tražnja za železničkim saobraćajem rasla i samim tim i potreba za više od jednog voza na pruzi,
bilo je potrebno razviti operativna pravila i sisteme koji će to omogućiti.
Međutim, osnovna premisa je ostala ista, kako za signalizaciju 19. veka, tako i za signalizaciju 21. veka.
A to je:
Vozovi se ne mogu sudariti samo ako im nije dozvoljeno da istovremeno zauzimaju isti deo pruge.
Kada su ljudi bili signali
Rekli smo da je bilo neophodno pronaći način za organizaciju saobraćaja više od jednog voza na istoj železničkoj pruzi.
U tu svrhu železničke pruge su podeljene na deonice koje su nazvane prostorni odseci.

Serbian: 
Na samom početku, muškarci, prvobitno nazvani „policajci“, bili su zaposleni da stoje na određenom rastojanju, formirajući neku vrstu
„ljudskih odseka“.
Bili su postavljeni duž pruge sa štopericom i ručnim signalima i obaveštavali su mašinovođu koji se približavao da je prethodni voz
prošao ranije ili kasnije u odnosu na određeno vreme.
Koristeći crvenu, žutu i zelenu zastavicu „policajci“ su pokazivali mašinovođama kako da nastave kretanje.
Crvena zastavica se pokazivala u slučaju da je prethodni voz prošao manje od pet minuta u odnosu na voz koji je pristizao.
Ako je voz koji je pristizao više od 5
5 i manje od 10 minuta nakon što je prethodni prošao, mašinovođi se pokazivao žuti signal upozorenja.
Zeleni signal pokazivao se samo u slučaju da je prošlo 10 ili više minuta od prethodnog voza.
Ovaj sistem je nazvan „sistem vremenskog intervala“.
Sistemom vremenskih intervala se pokušalo da se napravi interval sleđenja vozova koji bi zaštitio vozove ali su se  ustvari stvorili ozbiljni problemi.

English: 
In the early days of railways, men, originally called the 'policemen', were employed to stand at certain intervals, forming some kind of a
"human blocks"
They were placed along the line with a stopwatch and were using hand signals to inform the train driver of approaching train that preceding train
had passed more or less than a certain amount of time earlier.
The red yellow and green flags were used by policemen to show train drivers how to proceed.
A red flag was shown in case when the preceding train has passed less than 5 minutes before the approaching train arrived.
if the approaching train arrived more than 5
and less than 10 minutes after the preceding one has passed a yellow caution signal was shown to the train driver.
The full speed green signal was shown only in case if 10 or more minutes elapsed since the preceding train has passed.
The system was called "time interval system".
The time interval system while trying to use a headway to protect trains actually created some serious problems.

Serbian: 
Policajci nisu mogli da saznaju da li je prethodni voz napustio deo pruge ili jednostavno rečeno, potpuno napustio sledeći odsek,
pa u slučaju ako je prethodni voz iz bilo kog razloga zaustavljen,
osoblje voza koji se približavao ne bi imalo takvu informaciju osim ukoliko to ne bi bilo vidljivo iz njihove pozicije. Kao rezultat,
nesreće su bile česte u tim ranim danima, jer su u nekim slučajevima mašinovođe verovali da ih čeka 10 minuta razlike,
ali u stvari to nije bio slučaj.
Razlog zašto je ovo toliko važno je činjenica da vozovi zahtevaju značajno vreme i rastojanje da bi se zaustavili,
računajući od trenutka kada se zavede kočenje.
Danas ta rastojanja obično nisu manja od 700 m,
ali mogu biti i 1500 m,
pa čak i više, u zavisnosti od različitih faktora.
Još jedan ozbiljan problem, sa stanovišta tržišta, bio je kapacitet pruge.

English: 
The policeman had no way of knowing whether a preceding train had cleared the line ahead, or simply put, he had completely left next interval,
so in case of a preceding train being stopped for any reason,
the crew of an approaching train would have no such information unless it was clearly visible from their position. As a result,
accidents were common in those early days because, in some cases, train drivers believed they had a 10 minutes gap ahead of them,
but in fact that was not the case.
The reason why this is so important, is the fact that trains requires significant time and the distance in order to stop,
counting since the moment the braking is being applied.
Today these distances are usually no less than 700 meters or
2296 feet but they can also be 1500 meters or
4921 feet and even more, depending on different factors.
Another serious problem, from the market point of view, was line capacity.

English: 
Even if engineers could rely on trains not making unplanned stops,
the 10 minutes time interval significantly restricted the number of trains which could run on a given railway line over the certain amount of time.
As there was a need for more capacity, which meant more trains,
engineers gradually begun to reduce the time or the headway between the trains.
As expected ,as they reduced the headway, the number of trains per hour increased. Sounds simple, right?
Well, in fact, it's not. As the capacity increased,
the number of accidents also increased. Eventually, this showed the need to urgently change something. The solution was,
fixed track site signaling.
By the middle of the 19th century, many railway companies had developed some form of fixed track signals which
aim to replace hand signals and increase line capacity.
With the invention of telegraph and later the telephone,

Serbian: 
Čak i ako bi se inženjeri mogli osloniti da vozovi neće praviti neplanirana zaustavljanja,
vremenski interval od 10 minuta značajno je ograničio broj vozova koji bi mogli da saobraćaju na datoj pruzi tokom određenog vremenskog perioda.
Kako je postojala potreba za većim kapacitetom, što je značilo i više vozova,
inženjeri su postepeno počeli da smanjuju interval sleđenja između vozova.
Očekivano, kako su smanjivali interval sleđenja, povećavao se broj vozova tokom jednog sata. Zvuči jednostavno, zar ne?
Pa, u stvari nije. Kako se kapacitet povećavao,
povećavao se i broj nezgoda. Na kraju je ovo pokazalo potrebu da se hitno nešto promeni. Rešenje je bilo,
fiksna (stalna) signalizacija pored pruge.
Uvođenje mehaničkih signala
Do sredine 19. veka, mnoge železničke kompanije razvile su neki oblik fiksnih signala pored koloseka
sa ciljem da zamene ručne signale i povećaju kapacitet pruge.
Izumom telegrafa, a kasnije i telefona,

English: 
It became possible for the railway staff in charge for specific "block" to send a message to the staff in charge for the next one,
confirming that a preceding train had left their block, clearing the way for the next.
Mechanical signals first appeared in the UK in
1841 and the signal box with levers controlling remote signals and points in 1860.
Originally, the run of each train through a section was tracked visually by the signalman.
When the train had cleared his section, the signalman told the signal box operator on the approach side
That his section was now clear and that he could, if required "accept" another train.
The messages between signal boxes were transmitted by system of bell codes.
Also, to give an early warning of signal set danger, after some time, all signals were classified as either "home" or "distant" signals.
Why did this happen? Well, distant signals provided an opportunity of showing the indication or the condition of the signal ahead,

Serbian: 
postalo je moguće da železničko osoblje zaduženo za određeni odsek poštalje poruku osoblju zaduženom za sledeći,
potvrđujući da je prethodni voz napustio njihov blok, omogućavajući prijem sledećeg.
Mehanički signali su se prvi put pojavili u Velikoj Britaniji
1841. godine a postavnica sa polugama koje kontrolišu signale 1860. godine.
Čovek zadužen za signalizaciju je prvobitno pratio prolazak svakog voza kroz odsek.
Kada voz napusti njegov odsek, tada prenosi operateru na postavnici
da je njegov deo sada slobodan i da može, ako bude potrebno, "prihvatiti" drugi voz.
Poruke između postavnica prenošene su sistemom zvonovnih kodova.
Takođe, kako bi se što ranije upozorilo na signale koji pokazuju crveno, nakon nekog vremena svi signali su klasifikovani kao glavni ili predsignali glavnih signala.
Zašto se ovo dogodilo? Pa, predsignali su pružali mogućnost pokazivanja signalnog znaka ili stanja sledećeg signala,

English: 
I.e. whether the signal is showing "stop" or proceed. The introduction of distance signals provided an early sighting point and thus
Increased the available braking distance for a train crew, thus allowing higher train speeds.
"ith introduction of warnings,
it also became necessary to differentiate between indications show to train drivers,
and so yellow became distant signal color while the red and the green became "stop" and "proceed".
In some countries, and on some railway lines, this system of mechanical signals is still in use even today,
however, the next step of technological evolution broad improvement in terms of introduction of the color light signals.
Today, on most modern railways, the mechanical signals have largely been replaced by the color light signals.
Compared to mechanical ones, color light signals have the advantage of displaying the same aspects by day and by night,
and they also require less maintenance.

Serbian: 
tj. da li ovaj signal pokazuje „zabranu dalje vožnje“ ili „dozvoljenu vožnju“. Uvođenje predsignala omogućilo je ranije ukazivanje i na taj način
povećalo raspoloživi zaustavni put, omogućavajući tako veće brzine vozova.
Uvođenjem “upozorenja”
postalo je neophodno razlikovati signalne znake,
pa je žuta postala boja predsignala, dok su crvena i zelena postale „zabrana dalje vožnje“ i „dozvoljena vožnja“.
U nekim državama, i na nekim železnicama, sistem mehaničkih signala je još uvek u upotrebi.
Ipak, sledeći korak u tehnološkom razvoju je poboljšanje u pogledu uvođenja svetlosnih signala.
Moderni sistem signalizacije
Danas su na većini modernih železnica mehanički signali  uglavnom zamenjeni svetlosnim signalima.
U poređenju sa mehaničkim, svetlosni signali imaju prednost pokazivanja  istih signalnih znakova i danju i noću,
a takođe zahtevaju i manje održavanja.

Serbian: 
Iako se tipologija signala veoma razlikuje u različitim zemljama, a ponekad čak i između različitih železničkih sistema u istoj,
tipični osnovni sistem aspekata bio bi sledeći:
• Zelena: Nastavite najvećom dopuštenom brzinom na pruzi. Očekujte da sledeći signal pokazuje zelenu ili žutu boju,
• Žuta: Pripremite se za sledeći signal koji pokazuje crveno,
• Crvena: Zabrana dalje vožnje.
Osnovna ideja je bila da se ovim signalima ponovo podeli železnička pruga na različite prostorne odseke.
Tačnije, u modernoj signalizaciji zapravo postoje dva različita koncepta prostornih odseka, automatski pružni blok (APB) i pokretni blok.
Pod APB-om, signali pokazuju dali ili ne voz sme da uđe u naredni odsek na osnovu automatskog
otkrivanja zauzetosti narednog odseka i prema tome da li može da primi nadolazeći voz.
Kao što je predloženo na početku, pruga opremljena automatskim blokovima ili tzv. sistemom međuzavisnosti

English: 
Although typology of signals widely vary between different countries, and sometimes even between different railway systems within the same one,
a typical basic system of aspects would be the following:
Green: Proceed at line speed. Expect to find next signal displaying green or yellow
Yellow: Prepare for the next signal displaying red.
and red stop.
The basic idea was to use these signals, to again, divide railway line into different blocks
To be more precise in modern signaling. There are actually two different concepts of blocks. Automatic block and the moving block.
Under automatic block signaling, signals indicate whether or not a train may enter a block based on automatic,
on rails, train  detection indicating whether a block is clear and therefore able to accept the approaching train.
As suggested, at the beginning the line equipped with automatic blocks so called interlocking system

English: 
is divided into sections of length not shorter than the breaking distance of the fastest strain running on the root.
If we go further into details, there are two ways of detection of occupation of blocks.
The first one is using the track circuits.
It works on the following way: First the rails at both ends of each section are electrically isolated from the next and previous section.
Then, an electrical current is fed to both running rails at one end,
and, the relay which is located at the other is connected to both rails.
When the section is unoccupied, the relay coil is energized and it completes the electrical circuit of that block.
However, when a train enters the section, short circuits the current in rails, and the relay becomes instantly de-energized.
This simple system is then used as a basis for displaying different aspects of block signals.
Track circuits can be also used to automatically detect some kind of defect, such as broken rail.
The second way is axle counters.

Serbian: 
podeljena je na odseke dužine ne kraže od zaustavnog puta najbržeg voza koji saobraća na toj relaciji.
Ako idemo dalje u detalje, postoje dva načina otkrivanja zauzetosti odseka.
Prvi je korišćenje strujnih kola.
Strujno kolo funkcioniše na sledeći način: Prvo, šine su na oba kraja svakog dela odseka  električno izolovane od sledećeg i prethodnog odseka.
Zatim se električna struja napaja na obe šine na jednom kraju,
a rele, koji se nalazi na drugom, povezan je sa obe šine.
Kada je odsek slobodan, rele je pod naponom i čime se stvara strujno kolo tog odseka.
Međutim, kada voz uđe u odsek, on pravi kratak spoj i prekida kolo, pa rele gubi napon.
Ovaj jednostavni sistem se zatim koristi kao osnova za pokazivanje različitih aspekata prostornih signala.
Strujna kola se takođe mogu koristiti za automatsko otkrivanje neke vrste kvara, poput naprsle šine.
Drugi način su brojači osovina.

Serbian: 
Ovaj metod određivanja zauzetosti bloka koristi uređaje koji se nalaze na njegovim počecima i krajevima, koji broje osovine koje
koje ulaze i izlaze iz odseka. Ako je broj osovina koje napuštaju blok jednak onima koje su u njega ušle, pretpostavlja se da je odsek slobodan.
Na osnovu ovog koncepta uvedeni su unapređeni železnički sistemi kako bi se povećala bezbednost na železnici.
Ovi novi sistemi, sposobni da neprestano prate brzinu voza, nazivaju se ATP ili Automatski sistemi zaštite vozova.
Prvo su ATP sistemi koristili pokazivač brzine i zvučna upozorenja da bi savetovali mašinovođu
ako je voz, na primer, prošao signal koji pokazuje crveno ili prekoračio ograničenje brzine.
U tim slučajevima sistem pokreće automatsku kočnicu ako mašinovođa ne reaguje na upozorenja.
Jedan od ključnih principa ATP sistema je koncept modela kočenja,
matematički model koji omogućava predviđanje maksimalne bezbedne brzine voza. Jednom kada je poznat obrazac kočenja,
u realnom vremenu je lako odrediti

English: 
This method of determining the occupation of a block uses devices located at its beginnings and ends, which counts the number of axles that
enter and leave the block. If the number of axles leaving the block equals those that entered it, the block is assumed to be clear.
On the basis of this, interlocking concept, the upgraded rail signaling systems were introduced in order to increase railway safety.
These new systems, able to constantly monitor the speed of the train, are called ATP or Automatic Train Protection systems.
At first, ATP systems used a target speed indication and audible warnings to advise the train driver
if the train, for example, passed a red signal or exceeded a speed restriction.
In these cases, the system applies an automatic brake if the driver fails to respond to the warnings.
One of the key principles of ATP systems is the braking model concept,
a mathematical model which allows predicting the maximum safe speed of the vehicle. Once the braking pattern is known,
it’s easy to determine, in real time,

Serbian: 
koja je maksimalna brzina kojom vozilo može da saobraća, tako da se može bezbedno zaustaviti pre cilja ili neke opasne situacije.
Kada se govori o određivanju maksimalne brzine u realnom vremenu,
drugi koncept blokova, kao što je pomenuto, je sistem pokretnih blokova.
Za sistem pokretnih blokova, računar izračunava „bezbednu zonu“ oko svakog voza koji saobraća.
Sistem zavisi od poznavanja tačne lokacije i brzine svakog voza, što se određuje kombinacijom nekoliko senzora:
aktivnih i pasivnih markera duž koloseka i brzinomera u vozovima.
Sa podešavanjem pokretnog bloka, signali pored pruge više nisu potrebni, a uputstva sa koloseka se direktno prenose na vozove.
Ovo ima prednost u povećanju kapaciteta koloseka na maksimalnu teorijsku granicu,
omogućavajući vozovima da se približavaju jedni drugima, na dužini zaustavnog puta, uz održavanje zahtevanih bezbednosnih granica.
Treba pomenuti još jedan važan aspekt kako bismo vam pružili punu perspektivu modernih sistema signalizacije

English: 
what is the maximum speed at which the vehicle can travel, so it can safely stop before the target or danger point.
When speaking about determining the maximum speed in real time,
another concept of blocks, as mentioned, is a moving block system.
For moving block system, a computer calculates a "safe zone" around each moving train.
The system depends on knowledge of the precise location and speed of each train, which is determined by a combination of several sensors:
active and passive markers along the tracks and trainborne speedometers.
With a moving block setup, trackside signals are no longer necessary, and the instructions from the tracks are directly transferred to the trains.
This has the advantage of increasing track capacity to the maximum theoretical limit,
By allowing trains to run closely to each other, at exact breaking distances, while maintaining the required safety margins.
There is one more important aspect to mention in order to give you a full perspective of the modern signaling systems.

Serbian: 
Naime, napretkom tehnologije i povećanjem brzina mašinovođe čak više nisu u stanju da jasno prepoznaju signalne znake
koje daju signali kraj pruge. Zbog toga su sistemi bez signala pored pruge praktično postali neophodni.
U Evropi, brzina iznad koje se signali pored pruge više ne koriste iznosi
160 km/h.
Takođe ćemo napomenuti da su savremeni sistemi signalizacije zasnovani na
komunikaciji pomoću radio tehnologije, dok je projekat uvođenja 4G LTE tehnologije
već pokrenut u Južnoj Koreji.
Recite nam u komentarima ako ste zainteresovani za poseban video, koji detaljnije objašnjava ove vrste tehnologija.
Kao što smo videli, u dvovekovnoj istoriji železnice, železnička signalizacija je prolazila kroz proces stalne evolucije i prilagođavanja novim
tehnološkim i tržišnim okolnostima.

English: 
Namely, with the progress of technology and the increase of speeds, train drivers are no longer even able to clearly recognize the signal signs
provided by the trackside signals. This made the systems without trackside signals practically a must.
In Europe, the speed limit after which the trackside signals are no longer used,
is 160 km/h (100 mph).
We will also mention that modern signaling systems are based on
communication using radio technology, while the project of introducing 4G LTE technology
has already been launched in South Korea.
Tell us in the comments bellow if you are interested in a special video, explaining these types of technologies in more detail.
As we saw, in a two-centuries long history of railways, the railway signaling went through the process of constant evolution and adaptation to new
technological and market circumstances.

Serbian: 
Iako je osnovni princip zauzetosti segmenta železničke infrastrukture ostao isti,
kako je tražnja za železničkim saobraćajem rasla, ovaj segment je postajao sve kraći, sve do svoje minimalne mere.
To je zapravo omogućilo maksimalan teorijski kapacitet pruge. S druge strane, kako je tehnologija napredovala,
napredovao je i način prenošenja signalnih znakova mašinovođama:
od zastavica, preko mehaničkih i svetlosnih signala, do tačke kada signali više nisu ni potrebni, a kompletna komunikacija se odvija između između železničke
infrastrukture i kabine mašinovođe u realnom vremenu, automatizujući optimizaciju brzine voza i modela kočenja.
Nažalost, došli smo do kraja ovog videa. Hvala vam puno na pažnji,
nadamo se da ste uživali i naučili nešto novo o železnicama sveta.
Za kraj, naravno, za još priča o železnici, ne zaboravite da lajkujete ovaj video i pretplatite se na naš kanal! Zbogom.

English: 
Although, the basic principle of occupation of the segment of railway infrastructure remained the same,
as demand for rail traffic grew, this segment was becoming shorter and shorter, all the way to its minimal extent possible.
This actually enabled maximum theoretical capacity. On the other hand, as technology made progress,
so did the way of communicating the signal signs to the train drivers:
from flags, through mechanical and light signals, to the point where signals are no longer even requred and whole communication is done between the railway
infrastructure and the train drivers cab in real time, optimizing the train speed and braking paterns authomaticaly.
Unfortunately, we came to an end of this video. Thank you very much for your attention,
we hope you enjoyed and learned something new about the railways of the world.
For the end, of course, for more railway stories, don’t forget to like this video and subscribe to our chanell! Goodbye.
