Abstract: A position indicator (10) for a helmet (1), for example a bicyclist's safety helmet, comprises a protruberant diffuser (12) containing one or more electroluminescent strips (60, 61); at least part of the emitted light is distributed through the diffuser (12), preferably by means of an internal convex reflector (62) which contains the power supply (70, 71, 72). A second strip is preferably arranged to be directly visible through a transparent window in the diffuser (12). The indicator is releasably attached to the helmet, for example by means of magnets (30), and may be arranged to detach in the event of an accident so as not to impair the normal function of the helmet. The diffuser preferably forms an illuminated band extending along the side of the helmet (1); the front (15) and rear (16) ends of the indicator may be distinguished from each other. A position indicator system comprises two indicators arranged symmetrically on either side of the helmet, so as to indicate the orientation of the wearer.