In winter, just before I get to work, I drive along a busy road that heads straight into the low morning sun. There is an on-road bike path on the edge of the road, but it is still so difficult to see if there is anyone in that lane as you turn into the road. There was one young male cyclist who probably looked super-sexy in his black gear every morning - but who just couldn't be seen from the car. One morning I still had all my cycling gear in the car, including a $5 UV yellow with reflector stripes vest. I pulled up in front of the cyclist and when he came near, I just held out this vest to him. He stopped and asked what I wanted - I told him to please take the vest and wear it as I just couldn't see him on the road. He was slightly taken aback, but said thanks and put the vest on. I often see him in the morning now, wearing the vest - I always give a toot of the car horn just after I pass him and give him a wave.

The workers' vests have a fluorescent / UV thread in the weave so that they show up in sunlight and can be seen from a great distance. In the evening, the fluorescence does not react to artificial light which is why you then need the reflective stripes.