  The work in this paper is motivated by I. Bani\v{c}'s and A. Taranenko's
recent paper, where they introduced a new notion, the span of a graph. Their
goal was to solve the problem of keeping a safety distance while two actors are
moving through a graph and they present three different types of graph spans,
depending on the movement rules. We observe the same goal, but give a different
approach to that problem by directly defining the maximal safety distance for
different movement rules two actors can take. This allowed us to solve several
problems, prove some relations between different graph spans and calculate the
span values for some classes of graphs.
