Experiments under laboratory conditions were carried out to study the
ordering in bidirectional pedestrian streams and its influence on the
fundamental diagram (density-speed-flow relation). The Voronoi method is used
to resolve the fine structure of the resulting velocity-density relations and
spatial dependence of the measurements. The data show that the specific flow
concept is applicable also for bidirectional streams. For various forms of
ordering in bidirectional streams, no large differences among density-flow
relationships are found in the observed density range. The fundamental diagrams
of bidirectional streams with different forms of ordering are compared with
that of unidirectional streams. The result shows differences in the shape of
the relation for {\rho} > 1.0 m-2. The maximum of the specific flow in
unidirectional streams is significantly larger than that in all bidirectional
streams examined.Comment: 9 pages, 9 figures, 3 Table
