Wearing a Joe Rocket hi-viz jacket gets a noticeable reaction from drivers compared to a black leather Brooks jacket. With the black Brooks, more drivers tailgate and drive closer. With the hi-viz, more drivers keep their distance.
I have no idea why, but the effect is consistent. The hi-viz jacket is worn in the summer/warm weather and the Brooks in cold/cooler weather. One thing I have not tried is wearing the Brooks jacket with a hi-viz vest. I have noticed people burst out laughing when I wear the hi-viz jacket off the bike. That never happens with the Brooks, so I think it has something to do with the colors.