Article on JR East ATACS control system from Rail Engineer

[bikkuri bahn]

The concept of ERTMS Level 3 has been around since the vision for a standardised European signalling system came about in the 1990s. Reducing the amount of track-based signalling equipment and doing everything by radio seemed an admirable goal but, despite early predictions and the emergence of something akin on lightly used lines, very little progress has been made.

 

The reasons are complex and contain technical, safety and commercial elements. But is it so difficult? A recent IRSE seminar held in Japan learned of the JR East ATACS system that seemed to have very similar characteristics to Level 3 and was already in limited operation, so are there lessons to be learned?

http://www.railengineer.uk/2016/09/30/atacs-the-japanese-level-3/

 

*hat tip to dimlys1994 over at SSC forum for this

[kvp]

Not many info is around on ertms, but in Hungary it was installed on line 1, a legacy (1930ies) high speed line, today mostly known for the Railjet push pull high speed trains mixing with commuter emus and traditional passenger and freight trains. The install is mixed with a rail based continous signal analog system from the 1970ies and the old point based train stop system kept as a fallback.

 

Generally ERTMS works, but the number of failures due to signal loss is higher than with the rail based system. Most drivers, who could choose between the two systems usually choose to activate the rail based system as it allows higher speeds due to a more stable signal.

 

However the radio based variant was installed on two fully grade separated metro lines, one being driverless and having no backup system in place. They also work, but the usage is more simple and the radio antenne is a piece of wire hung on the tunnel ceiling, so signal quality is always good. (sideeffect: the 3G internet is also stable)

 

The japanese system uses the distance counter with balise based reference points solution alone, so doesn't rely on gps signals at all. The multiple frequency solution described in the article is the same as the basis of the gsm mobile phone system used by the european system. The cell info can be also used as a fallback for position finding. It would be interesting to see how multiple lines near each other will be managed as it requires base tower (cell) frequency coordinations on a 3D map. The 9600 baud of the japanese system looks low compared to the 3G/4G speeds (millions of baud) available on the european system. This could limit the number of trains around each base (cell) tower. I don't know the packet size, but using dcc as a reference 9600 bauds with 1 packet/train/second means 240 trains per center. This might just work but in Tokyo it might proove to be inadequate as lines running near each other have to share the radio bandwidth. (i'm pretty sure the Tokyo area has more trains running at the same time)

 

So, thanks for the link. The article was intresting and more info (mainly packet and data formats) would be welcomed.

[utrainia]

Interesting article, thanks. Kvp: the base stations are 3km apart according to the article, so that should provide ample bandwidth to each train at 1 packet/s.