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Old August 6th, 2014, 12:30 AM   #21
Silly_Walks
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Quote:
Originally Posted by K_ View Post
One reason is that it is hard to convince cash strapped railways to invest in a new system when a perfectly good system already exists.

The German LZB for example is a good system, and replacing it with ETCS doesn't really increase safety. The same applies for TVM in France, or ATB in the Netherlands.
Don't know about the other systems, but ATB should not be in there.

It is rather outdated, especially compared to ERTMS. The maximum speed is 140 km/h, there is no protection below 40 km/h and red lights can be crossed.

Money is an argument not to change it, but a "perfectly good system already existing" is not the case.
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Old August 6th, 2014, 12:58 AM   #22
AlexNL
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From a technical point you are half right: ATB-EG (Eerste Generatie, First Generation) does not work under 40 km/h, but there is no technical 'upper limit'. The 140 km/h limit is set by regulations (and thus set as a parameter in the trains), but it is not a design limitation.

What the ATB-EG system does well is that there is a constant relay of information from track to train: a train can immediately accelerate when a signal aspect improves, it doesn't have to pass a beacon first.

What it doesn't do well is that it only knows a couple of modes:
- Max speed 40 km/h
- Max speed 60 km/h
- Max speed 80 km/h
- Max speed 130 km/h
- Max speed: maximum rolling stock speed (in practice this is hardwired to 140 km/h)

If you have a section of track that is certified for 90 km/h, the trackside infrastructure has to give clearance for 130 km/h, otherwise the train can never go 90 km/h. Furthermore, there is no protection underneath 40 km/h (where most accidents happen) and even at higher speeds the system is not fool proof. If an engineer brakes just lightly the system is satsified and allows red signals to be passed at 130 km/h.

Overall, ATB-EG does a good job but it could do a better job if it were re-built according to 21st century standards. This is where ETCS L2 comes into play...
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Old August 6th, 2014, 08:35 AM   #23
M-NL
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Originally Posted by KingNick View Post
I asume the dotted lines into Germany indicate that there is no ETCS installed at the moment?
No they just mean that they are abroad and that the foreign track authority (DB Netz for Germany) is responsible for the safety system. However most of these border crossings are already equipped with eurobalises to indicate to the passing trains a safety system and overhead line system change is about to happen.

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Overall, ATB-EG does a good job but it could do a better job if it were re-built according to 21st century standards. This is where ETCS L2 comes into play...
If they hadn't come up with ATB-NG, but would would have gone with ATB-EG with balises for extra functions it could have been a nearly perfect system. If they had also changed the 75Hz carrier frequency to something that isn't a harmonic of 50Hz at the same moment fitting ATB to 25kV AC tracks also would have been possible.
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