I went out twice today for leisure, and both times I was only wearing my club kit and not my hi-viz jacket as it was nice and warm. On both occassions, I didnt encounter more or less bad driving than I usually do (driving has seemed to have improved in my area dramatically recently for some reason).
If drivers look, then they are aware and it is just their misjudgements which cause problems. If they dont look, then there is an obvious answer if something happens.
The only time when hi-viz would help is at night. Unless you are wearing some kind of urban camouflage, drivers will see you if they look in the day.
Police and road safety teams should be looking to improve driver awareness. That is the real cause of problems on the roads. The majority of drivers do have the skills to drive properly, but cannot understand the need for having a good look around themselves at junctions in case something might be coming.
Our money can be spent on better things other than giving out free hi-viz.