[northwind]

If you wear a rucksack, you can buy hi-viz rucksack covers...

Personally, I'm not convinced they do much except in bad visibility. I'm more convinced as to how useful they could be if you manage to come off your bike on a dark road! I've always thought that in daylight, if they don't see a bike they won't see a vest, and at night you have the tail or headlight, but come off the bike and you have neither, you're just a dark shape on a dark road. If I'm down and hurt, or down and out, I'll take any edge I can get.

PS, don't buy those cheap "reflective" vests you see, they're rubbish. Real hi-viz isn't expensive, but it's far more effective. Get proper rated stuff if you're going to get it at all, or you're just playing.