Two traffic signal structures recently collapsed in Wyoming. The collapse was a result of brittle fracture of the connection between the cantilever signal light support arm (mast arm) and the vertical pole (post) caused by wind-induced, largeamplitude vibrations of the mast arm. This paper presents the problem, the proposed test program, the results of initial development tests, and the effort to develop a viable AE testing technique along with evaluation criteria that can be used to screen in-service traffic signal poles.