Ok 'suppose I'd better admit to my winter riding garb...
Summertime I don't bother with Hi-viz and only use daytime lights abroad (often required by law) or in heavy traffic/known bad areas in town.
If they're not looking in the first place.... there are times I'm pretty sure I could have Jo Guest standing naked on my shoulders (hmmm, yes please!) and they still wouldn't notice the bike about to hit them

Commuting in this weather/time of year though.. I invariably wear a medic hi-viz vest*, the reason is simple... some car drivers notice a nice visible bit of scotchlite, but many automatically mentally discard it. It's not malice, we're just not in their mental list of things which "matter" to them while they're driving.
My three band "h" pattern scotchlite with badge panels and a (green and white) chequered band on the bottom, now at a glance, or when the headlamps flash over it, it looks emergency services... and that *IS* on their "need to know" driving list

Most will then look closer and choose to ignore me, *but*, they've properly noticed me. Many, surprising how many, will immediately drop to 30mph exactly (or whatever the local limit is) and start driving very carefully.
It's like taking off a cloak of invisibility about 30% of the time. Thoroughly recommended, and I've just ordered a new vest as the old one is knackered, this tight jock just spent three times the price of a "standard" vest because I'm so convinced(!)
Just don't go dressing up as Policemen ok, they get upset about it

(Although ebay have some "decomissioned" police jackets that I was tempted by.. I just can't quite bring myself to wear a blue chequer

I'm pretty sure it would be even more effective... but it would worry me)
Smudge
*I can and will give first aid to anyone I meet who needs it, and am First aider at work so I don't feel I'm "cheating" wearing the first aider chequer/logos. I think there is a picture of me somewhere in the site leaving the dragon wearing it btw.