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Moves vehicles from the inlinks' buffer to the outlinks where possible.
The inLinks are randomly chosen, and for each link all vehicles in the
buffer are moved to their desired outLink as long as there is space. If the
front most vehicle in a buffer cannot move across the node because there is
no free space on its destination link, the work on this inLink is finished
and the next inLink's buffer is handled (this means, that at the node, all
links have only like one lane, and there are no separate lanes for the
different outLinks. Thus if the front most vehicle cannot drive further,
all other vehicles behind must wait, too, even if their links would be
free).