  It is shown that the branch of the empirical fundamental diagram for
congested traffic strongly depends both on the type of the congested pattern at
a freeway bottleneck and on the freeway location where the fundamental diagram
is measured. Since the type of the pattern at the same bottleneck can depend on
traffic demand, a qualitative form of the empirical fundamental diagram can
strong depend on traffic demand also. At freeway locations where the average
speed in synchronized flow is higher the branch of the fundamental diagram for
congested traffic has a positive slope in the flow density plane as well the
slope of the branch for free flow. In the upstream direction when the average
synchronized flow speed inside the congested pattern decreases, first the slope
of the branch for congested traffic decreases and then the branch can transform
into the curve with a maximum. At freeway locations, where the average speed in
synchronized flow further decreases the branch for congested traffic more and
more tends to the line J which represents the stationary motion of the
downstream front of a wide moving jam in the flow-density plane: The line J is
an asymptote for the branch of congested traffic of the empirical fundamental
diagrams at higher densities for those freeway locations where wide moving jams
occur and propagate.
