rather than being cached in the StaticRTree. This means we
can freely apply traffic data and not have stale values lying
around. It reduces the size of the RTree on disk, at the expense
of some additional data in RAM.
Fixes issue #1864. Given the simple set-up:
a --> b --> c
^-----------|
This would translate into an edge based graph (ab) -> (bc),
(bc) -> (ca), (ca) -> (ab).
Starting at the end of the one-way street (ab) and going to
the beginning, the query has to find a self-loop within the
graph (ab) -> (bc) -> (ca) -> (ab), as both nodes map to the
same segment (ab).
