The original idea behind hi-vis clothing is sound. To make you more visible to others when in a vulnerable position. Today that advantage is negated by the ubiquitous usage of hi-vis by people that have no need to wear it. As an example, at King's Cross station yesterday you could see orange, yellow, blue and green hi-vis being worn by people who were not at risk yet it is part of their uniform. There is no need for customer service jollies in airport terminals or security staff or anyone not airside to wear hi-vis. It seems that hi-vis has become a badge of identity and as such dilutes the real purpose of it.