  The safety region of operation of a system is the subset of allowed outputs
for which no undesirable outcome would occur. Knowing if a system would ever
leave its safety regions of operation is important information for the planning
and control of systems. The computation of the set of outputs also known as the
reachable set of the system is, in many cases, intensive and a simple
overestimation of it is preferred, instead. There are several perspectives to
address this problem including set-based approaches, Mixed-Monotonicity,
Hamilton-Jacobi reachability, neural networks, and recently reachability via
Chen-Fliess series. In the present work, a Chen-Fliess series representing the
input-output behavior of a dynamical system along with interval arithmetic is
used to overestimate the reachable set of a system. The advantage of this
combination of techniques is that it provides a closed-form of the
overestimating set. Examples are presented to illustrate the results.
