Until now the two lanes of a Kreisel were joined by a pair of edges in both
directions, because the travel direction was unknown. The CSV does carry it in
the Drehrichtung merkmal, so the arrow inside a Kreisel is now directed:
UZS clockwise -> material runs right to left, R -> L
GUZ counter-clockwise -> material runs left to right, L -> R
If the merkmal is missing or holds anything else, the circuit stays bidirectional
and that is reported as a warning, so an unknown value cannot silently invent a
direction.
The direction is visible in the drawing: the edge carries the rotation as its
label and the Kreisel cluster header states it in words, e.g.
"Kreisel Kreisel3 [0009] UZS (rechts nach links)".
Since a Kreisel is now traversed one way only, lanes can end up without an
outgoing or without an incoming connection. build_graph reports both cases,
naming the separators that sit on the affected lane, because such a lane means
carriers can either not leave or not reach it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
s.ayadi
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