Last week, I toured with two friends along a two-lane highway. One of my friends wore a florescent vest, and the other didn't. While riding through a forest, I noticed that the one without the vest was almost invisible while in shadow. And it was a sunny day. On the other hand, the one wearing a vest stood out like a sore thumb.
So if you are seriously interested in being more visible to car and truck drivers, wear a florescent vest. Making yourself easy to spot is an asset when sharing the road with fast-moving vehicles.
Something like this:
