[Tagging] Feature Proposal - RFC - 3rd and 4th rail (Michael Reichert)

Garry Keenor garry.keenor at gmail.com
Sat Jun 13 16:49:19 UTC 2020

Paul - thanks for the response. I struggle with the idea that someone would
know that a route is electrified with a ground level contact system, but
not how many rails there are. The possible sources are a) local knowledge,
b) wikipedia and c) aerial imagery. All of these will, 9 times out of 10,
define the system. Also, there are only 2 networks that I can identify
worldwide that are 4th rail, and I've tagged them both already. :-)

best regards,


On Thu, 11 Jun 2020 at 12:49, Paul Allen <pla16021 at gmail.com> wrote:

> On Thu, 11 Jun 2020 at 08:57, Garry Keenor <garry.keenor at gmail.com> wrote:
>> Re: using electrified=rail to mean (3rd or 4th rail)
>> I'm not in favour of this one - railway electrification engineers (of
>> which I am one) do not consider 4th rail to be a special case of 3rd rail,
>> but rather a distinct system with its own electrical feeding arrangement.
>> It would also run the risk of confusion in the mappers mind - they would
>> read as far as electrified=rail in the tag wiki and miss the later option
>> for 4th rail. I'm happy to leave electrified=rail to mean 3rd rail if that
>> is what the group prefers.
> Using electrified=rail to mean 3 rails and having a sub-tag for 4 rails is
> a bad
> thing.  But perhaps there is a case for retaining electrified=rail to mean
> "It's
> electrified using rails rather than contact line but I don't know how many
> rails."
> You mentioned that contact lines are often visible on aerial imagery.
> Mappers
> may know a route is electrified by other means (such as a newspaper article
> saying the route has been electrified) but don't know how many rails there
> are,
> only that there is no sign of a contact line.
> Argument against it: there may be a contact line but the imagery is too
> coarse for it to be visible or the mapper doesn't have the skill to
> interpret the image correctly so uses electrified=rail where it
> should be electrified=yes.
> --
> Paul
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