I wear cycling-specific clothes when commuting, so instead of the construction worker vest, all my commuting tops (jerseys, long-sleeve shirts, jackets) are hi-viz. AlertShirt.com is a good source for the construction worker stuff, and hi-viz t-shirts. I like their long-sleeve wicking t-shirt in the 'tween seasons.

I also run daytime running lights. I have a DiNotte 200L-AA in front, and a DiNotte 300R in back. See DiNotteLighting.com. There are now some less expensive blinkies that seem okay in the daytime. Sadly, most still are toys.

Your positioning in the lane also can improve visibility. Too far right and you're not noticed. This is especially true at intersections. Drivers look where they expect other cars to be. That's where you want to place yourself--where drivers are already looking.