Origins of Japanese rail signal aspects

[eldomtom2]

Does anyone have any info on this topic? I can't find anything.

[bikkuri bahn]

Answering before this becomes a zombie. I am not sure what you mean by origin, do you mean the history of early signaling?  If so the simple answer is a mixture of British and American practice, with bias towards the British.  Basically speed signaling now with some American practices such as position light signals ala Pennsy (though not as a primary signal, but rather intermediate where the primary signal cannot be seen due to curves or other visual obstruction).  As detailed English language info on Japanese railways is piss poor on the internet (always has been, and probably always will), best to access the Japanese wiki page and run a translator through it. AI assist has developed to the extent that translation has been improved greatly compared to say, five years ago.

https://ja.wikipedia.org/wiki/日本の鉄道信号

 

[eldomtom2]

I'm talking specifically about the signal aspects - I can find plenty of sources saying what they are, but none about how they developed (except for a single one about the flashing G/Y used on Keikyu). I'm particularly interested in the 減速 (YG) and 警戒 (YY) aspects.

 

Also Japanese signalling is not speed signalling in the regular sense (what I like to call "speed signalling at junctions"), it uses route signalling at junctions. What Japan has is "progressive speed signalling", which is a completely different from

[miyakoji]

The history and development sounds like truly specialist information.  The Japanese Wikipedia page, through Google translate (link below), just says it was initially developed from British technology, as Bikkuri wrote above.  I also tried searching on 日本の鉄道信号の歴史, but the few substantial pages I found were just copies of Wikipedia.

 

Japanese Wiki does have this about the YG and YY aspects (through Google translate)

• Deceleration indicator - the YG signal, which is lower than the G signal and higher than the Y signal, shows green and orange-yellow lights and indicates that a caution or warning signal is to be displayed at the next signal.  On Japanese National Railways, this indicated a speed of 65 km/h or 75 km/h.

• Warning sign - the warning indicator (YY indicator) is two orange and yellow lights, and is used when the next signal indicates a stop signal or a stop position, and when the block section is short and there is a short margin for overrunning, etc. The speed indicated to proceed is 25 km/h, but trains with speed control functions can indicate an alternative speed within the range that allows them to stop.

 

https://ja-m-wikipedia-org.translate.goog/wiki/日本の鉄道信号?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp

[Socimi]

For how the "specific aspects" developed within Japanese signalling, of course the "base three" - clear green, caution yellow and danger red - are universal all around the world and are derived directly from semaphore practice (Yellow replacing the "caution" aspect of a yellow-painted distant semaphore).

 

Now, for 減速 (Yellow-Green) and 警戒 (Double-Yellow), my theory is that the two aspects were directly lifted out of US rulebooks "imported" to Japan.

The current color-light signalling system was introduced in Japan not by the government railways (wich would hold onto the semaphore system for decades), but by the small private electric railway companies that were springing up all over Japan in the early 1900s (if i recall correctly, Keihan railway was the first to introduce the modern multi-color signals with oval heads in 1912 or thereso, wich have been the standard ever since). These companies based their whole structure and operational practices, including signalling, on US interuban electric railways, wich were already using various signalling rulebooks derived (but not exactly quite) from mainline railroads.

 

For example, the Yellow-Green aspect in US practice - in it's exact "Japanese guise" as "Yellow over Green" - is known generally as the "Approach Medium" (or "Proceed at Limited Speed", or "Approach Advance" for AT&SF) in many US rulebooks, and generally carries the same meaning as in Japan: a train may proceed (or "approach" the signal), but must do so at "medium" speed lower than the line's speed, but not necessarily a "slow" (shunting-like) speed.

 

The speed limit carried by a Yellow-Green signal in Japan depends by the railway (for JR and other ex-JNR lines it's 65Km/h, for Kintetsu it's 95Km/h) but nonetheless it still remains an "intermediate" speed between line speed (the maximium allowable line speed in Japan is 130Km/h, barred the two lines with "high-speed clear" signal aspects allowing 160Km/h) and "slow" shunting speed.

 

Likewise, the double-yellow signal is another US-derived aspect, wich is known generally as "Approach Slow", and again carries mostly the same meaning as in Japan: a train may proceed, but must do so at a "low" speed, generally equal to "shunting" speed. For Japan, this is generally 25Km/h, altough again, variations from railway to railways do exist.

 

Various and miscellanea:

- US signalling rulebooks vary widely from railroad to railroad, thus pinpointing a common name to a precise US signal aspect is quite hard (for instance, an "Approach Medium" is a double-yellow on Union Pacific, and yellow-over-green on the Santa Fe railroad).

(For the record, Italy's signalling system is also US-derived, but much more strictly so - it is essentially a carbon copy of the searchlight system and it's convoluted workings - we are the only country in europe with red-green or even red-yellow-green flashing and non flashing aspects!)

 

- The first color-light signals and correlated equipment imported in Japan by Keihan Railway were made by the Union Switch & Signal company.

Subsequent signal production was likely undertaken under-license from US&S by a variety of japanese domestic manufacturers.

As i pointed out in another post, US-style searchlight signals (single-head signals only, displaying clear, caution or proceed aspects) were also installed at various locations, but remained very few and far between.

 

 

[eldomtom2]

On 8/12/2024 at 4:37 PM, Socimi said:

For how the "specific aspects" developed within Japanese signalling, of course the "base three" - clear green, caution yellow and danger red - are universal all around the world and are derived directly from semaphore practice (Yellow replacing the "caution" aspect of a yellow-painted distant semaphore)

To nitpick here, Britain for instance only started using yellow-painted distants at about the same time as the first trials of colour light signalling - previously they were also red. The same may apply to other countries.

On 8/12/2024 at 4:37 PM, Socimi said:

Now, for 減速 (Yellow-Green) and 警戒 (Double-Yellow), my theory is that the two aspects were directly lifted out of US rulebooks "imported" to Japan.

The current color-light signalling system was introduced in Japan not by the government railways (wich would hold onto the semaphore system for decades), but by the small private electric railway companies that were springing up all over Japan in the early 1900s (if i recall correctly, Keihan railway was the first to introduce the modern multi-color signals with oval heads in 1912 or thereso, wich have been the standard ever since). These companies based their whole structure and operational practices, including signalling, on US interuban electric railways, wich were already using various signalling rulebooks derived (but not exactly quite) from mainline railroads.

 

For example, the Yellow-Green aspect in US practice - in it's exact "Japanese guise" as "Yellow over Green" - is known generally as the "Approach Medium" (or "Proceed at Limited Speed", or "Approach Advance" for AT&SF) in many US rulebooks, and generally carries the same meaning as in Japan: a train may proceed (or "approach" the signal), but must do so at "medium" speed lower than the line's speed, but not necessarily a "slow" (shunting-like) speed.

 

The speed limit carried by a Yellow-Green signal in Japan depends by the railway (for JR and other ex-JNR lines it's 65Km/h, for Kintetsu it's 95Km/h) but nonetheless it still remains an "intermediate" speed between line speed (the maximium allowable line speed in Japan is 130Km/h, barred the two lines with "high-speed clear" signal aspects allowing 160Km/h) and "slow" shunting speed.

 

Likewise, the double-yellow signal is another US-derived aspect, wich is known generally as "Approach Slow", and again carries mostly the same meaning as in Japan: a train may proceed, but must do so at a "low" speed, generally equal to "shunting" speed. For Japan, this is generally 25Km/h, altough again, variations from railway to railways do exist.

But this explanation doesn't quite add up to me, unless the interurbans used a quite different signalling system to the mainline railroads. Yellow over Green, in American practice, is a signal head displaying yellow above a signal head displaying green. 減速, on the other hand, is a single signal head displaying both yellow and green lights. This is because the basic logic of this American style of speed signalling at junctions evolved out of the practice - still used in Japan - of having one signal head for each route. The American evolution was to group routes together depending on speed. When you see a junction signal in Japan, one head displaying YY and the other displaying R, you are seeing a completely different basic logic to that of American speed signalling.

 

In addition, normally in America these two-light aspects are used pretty much only when junctions are involved - unlike in Japan, where they are primarily used to inform the driver of an upcoming stop signal - I don't know if they're used for what the UK would call approach control or not in Japan.

 

Does anyone have examples of colour light signals used on turn-of-the-century interurbans? That could clear some stuff up.

[brill27mcb]

Turn-of-the-century electric interurban railways in the U.S. basically did not go beyond a three-aspect signal, and those would have been on the lines with high engineering standards. Many ran with much less that that, making "meets" at passing sidings along a single-track line.

 

Rich K.