Visibility is a problem for bicyclist both at night, and during the day. After a lot of years I've decided that it's better to be extremely visible than to be invisible but know that you are and try to hide on the road.
To that extent I bought the lime colored survey's vest. It's a class 3 highway rated vest. That is to say you can work on a 55+mph road wearing this.
A couple of things to note: This vest has pockets. When I'm commuting it's very handy to have a place to put things when I'm walking from where I lock my bicycle up into the office. The vest is made of a mesh fabric. I'm not looking for warmth or wind or rain protection with this vest. I do wear it on top of everything else and therefore I don't have to care what color my rain coat is, although it's also bright orange. Or my jersey which are bright but not as bright as these colors.
I picked a velcro fastened front. It doesn't really matter. I have a friend who bought the zipper front one and they both fit about the same.
Lastly this vest has reflective tape on the sleeves. That's good for cross street traffic and when you are leaning down on the drops even if your chest is partly covered by your arms, there is some reflective materiel showing in all directions.
The minor disadvantage of wearing a vest on top of your rain coat is that it tends to keep the vents a bit more closed. I work pretty hard riding so it doesn't really matter. If it's pouring I'm wet, either from the inside because I've got everything closed up, or the outside because the vents also let water in.
Lastly who else wears reflective vests? Yeah you got it, cops. Want to hit a bicycle cop? I thought not. Now while I don't look like a cop up close at 100yds from the rear can you be sure? No, better slow down until you are sure. And thus the vest has accomplished it's goal, I've been noticed and cars passing me do so more carefully than without it.
Add reflective gloves, and flashing red lights and stick your arm out to signal a turn, and people pay attention.
You can get your own vest from any place that caters to construction workers. Or order it from Western Safety or Amazon.com http://www.westernsafety.com/