Wasn't there a report recently saying that HiVis on the lower leg was the most effective position for visibility?
That's certainly my anecdotal experience of spotting cyclists on the road at night. Altura Night Vision tights are outstandingly attention-grabbing in a way that screams 'cyclist' (I'd say more effectively than flashing rear lights), and you can identify a ninja BSOist by the motion of a single pedal reflector at surprising range.
I'm sceptical of how much this stuff actually reduces accidents, but the way I see it, if you're going to make cycling-specific longs, cycling-specific shoes, trouser-retention straps, etc. they might as well have some reflective on them. (FWIW, I consider pedal reflectors to be a Good Idea where the design can reasonably accommodate them.)
Requiring participants in a cycling event wear reflective ankle straps is another matter entirely, but it seems somewhat more evidence-based than requiring them to wear hi-vis bibs.
