Hi,

Am 20/04/2020 um 16.26 schrieb hanhmissi.tran@everysens.com:
> I have read https://wiki.openstreetmap.org/wiki/OpenRailwayMap/Tagging but I'm a bit confused about how to know if a track can be used in both directions.
> For a given way, should I rely on the value of the key oneway and on the value of the key railway:bidirectional ?
> And I'm confused about the description of the value "possible" for the key railway:bidirectional. Does it mean a way with that value may be bidirectional or not ?

TL;DR If you need the direction of a track for routing purposes, use
railway:preferred_direction=*, and oneway=* as fallback.

There are a couple of tags regarding the preferred or usual direction of
traffic on a track.

oneway=* is odd in railway context and I would not use it at all because
in almost any case a track can be used in both directions— often with
limited safety (see below). Most usage of oneway=* on railway track is
wrong.

railway:preferred_direction=forward/backward/both indicates whether the
primary direction of traffic the track is intended for is forward,
backward or in both directions. This tag is used outside a station on
double-tracked railway lines (both is common in stations and on
sigle-track lines). That's what I would use for routing. This tag is
used a lot in France (at least the eastern half) and a bit in Germany
and elsewhere. Check its presence in our test cases before you try it
out. ;-)

railway:bidirectional=* indicates the safety level of trains running
against the usual direction on double-track lines (the tag is intended
for the usage outside a station).

railway:bidirectional=regular means that the same safety level w.r.t.
interlocking is available, i.e. the interlocking in the signal box
ensures that no other train is on the segment ahead.

railway:bidirectional=signals means that there are signals for trains
using the track against the regular direction but there a limited or no
mechanisms in the interlocking to ensure that the track ahead is free.

railway:bidirectional=possible means that there are no signals and no or
nearly no safety mechanisms in the interlocking for trains running
against the regular direction. These trains usually need some kind of
manual command by the dispatcher (written sheet of paper, a phone call
or similar depending on the rules of operation). There are no or nearly
no mechanisms ensuring that the track ahead is free, all safety relies
on the staff at the signal box.

Best regards

Michael

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