Circuit-Cocircuit Reversing Systems in Regular Matroids

We consider that two orientations of a regular matroid are equivalent if one can be obtained from the other by successive reorientations of positive circuits and/or positive cocircuits. We study the inductive deletion-contraction structure of these equivalence classes in the set of orientations, and we enumerate these classes as evaluations of the Tutte polynomial. This generalizes the results in digraphs from a previous paper.