In addition to the two polarization modes present in general relativity, some modified theories of gravity may contain up to four additional polarizations, which are allowed to travel at different speeds. Detecting these additional modes would be evidence of new physics, but disentangling these modes from those in general relativity requires more than two detectors. In this talk, we discuss a new observational signature of additional, superluminal polarizations that can be searched for with currently available detectors. We here describe this signature and how to search for it in current and future data.