Considerable research is needed before any positive steps are taken to further the general use of modulated high-beam headlamps as motorcycle conspicuity aids. Such research cannot proceed satisfactorily without rigorous measurements of the visual characteristics of a modulating device, which have so far been lacking. The purpose of this paper is to provide an example of such measurements and, in particular, to report on the measurements of the relevant photometric characteristics of the Q-Switch modulating device. The results of these measurements demonstrate that the device falls within the specifications recommended by the authors for an extended flashing-signal code to be used by motorcyclists and moped riders, and clearly show that measurements in field conditions will form an essential part of any future conspicuity program based on lights.