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On Greek suburban railway (proastiakos) I noticed that on stations have an internal rail as long as the train platform:

Internal rail inage on proastiakos service greece

I was wondering what it the use for this internal rail? Also the suburban railway is electric and uses overhead lines and not a third rail layout.

The rail does not extend beyond the platform (I think it is even a bit shorter).

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    It is not even used. I was at first tempted to say it is an electricity pickup rail, as used (by some systems) in the UK, but the lack of wear on the inner rail suggests it is to accommodate an occasional train with a different gauge. "Standard gauge" is implemented on 55% of the world's railways, and Greece has different gauges, for example the Peloponnese metre gauge network. But a scale ruler applied to your picture does not support my theory, nor does the fact that the rail is only at the platform. – Weather Vane Jul 26 '17 at 18:30
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    Could the trains have an additional grounding brushes that come in contact with this rail in the stations to avoid stray currents or static while people are entering / exiting? – user13044 Jul 26 '17 at 18:54
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    I've seen this setup many places in the US. I've generally seen it at switches and junctions and on curves, and I've assumed the intent is to hold the cars on the track vs letting them drift over enough to have one wheel fall off the rail. However, it may be as dunni suggests that it's to help contain a derailment vs to prevent one. – Hot Licks Jul 26 '17 at 22:47
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    @Tom No. The wheels of the train provide a solid electrical connection to the rails, because the rails are used as the return conductor for the electrical supply. A brush would actually provide a much worse electrical connection, because the wheels are continually polishing oxidation away from the tracks, exposing fresh metal. Not so on the third rail. This is all different from the rubber tires of a race car, which are insulators, allowing the car to build up a static charge. In that case, measures like conductive brushes and carbon additives to tires to avoid static charges do make sense. – nitro2k01 Jul 27 '17 at 2:19
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    The answer and comments make sense, but I suspect you'd get an even better answer on area51.stackexchange.com/proposals/105759/… – WGroleau Jul 27 '17 at 3:08
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At least here in Germany such additional rails are used in sensitive areas, like stations, bridges etc., to prevent extensive damage in case of a derailment. If a car were to derail away from the platform (in your case), the third rail would still hold the car and would prevent it from drifting too far apart (and probably overturning etc.).

Here is such an example:

enter image description here Führungsschienen auf einer Brücke. Source: Wikipedia

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    +1. I've seen these in the UK as well, and especially if the platform's only on one side (with nothing to be worried about damage to on the other), this would make total sense. – jacoman891 Jul 26 '17 at 21:11
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    I looked this up a while back for the CTA's 'L' lines (Chicago metro rail): chicago-l.org/FAQ.html#3.4 – Nick T Jul 26 '17 at 22:43
  • @NickT That should be an answer! – Fabio Turati Jul 27 '17 at 1:25
  • @FabioTurati it's basically the identical answer as dunni's: to prevent more problems in the event of a derailment. I guess the first point might be relevant to Hot Licks' question-comment on the question, maybe. – Nick T Jul 27 '17 at 3:13
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This is called a Guard rail. These are placed in areas with restricted clearance to prevent excessive damage in case of derailment. In this case, it prevents a derailed train from hitting the platform where passengers are standing and/or other passenger trains.

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    It prevents the train from failling into the middle of the tracks and blocking the other track. – user207421 Jul 28 '17 at 4:27
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    @EJP Blocking the other track is not so bad. Killing a dozen of passengers is. That's why the guard rail is present in passenger stations but e.g. not in freight parks. – Dmitry Grigoryev Jul 28 '17 at 8:07
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It's also used by a switch to allow passenger trains to reach a platform, while freight trains just hiball through without using the switch, giving them more clearance. Here's an example, from the Westside Express Service of Tri-Met in Metro Portland, Oregon, which is operated by the Portland and Western line, at the Tualatin station. See https://imgur.com/gallery/31nSCZw

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    No, that can't be it because to OP describes (and shows) only one additional rail. – Henning Makholm Nov 5 '18 at 15:56
  • What you've posted is an example of a Gauntlet track, which is not the same thing. – Mike Harris Nov 5 '18 at 23:25

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