..It's taken time but I have convinced a few cyclists to spend more money on ultra-bright front lights (daytime, 1000+ lumen flashing) and rear lights (300 lumen) and have them on at all hours of the day...
This reminds me of the old light bulb joke. How many psychiatrists does it take to change a light bulb? Only one, but the light bulb really has to want to change.
Having observed how people behave with respect to safety over 5 decades, I do have some observations.
1. Good examples will change some people's behavior. My wife runs DRL because I do.
2. An emotional engagement, not a rational one, is needed to change a deep-seated behavior. Usually, you need a "teachable moment" to get someone to change, and you can't program that.. it is on their schedule, not yours. Outside of a teachable moment, I find that a personal story related directly can have an emotional impact. For instance, if you crashed (or near-miss) because someone pulled out in front of you, relating that and your decision to run DRL can work. But you need some connection to the person and it isn't fast.
3. Teenagers? Fuggedaboutit. My daughter is programmed to not do what I tell her. Once, she asked what road rash was and sure enough, the next day she got a bad dose. I use that now as a reminder to her that the unexpected can happen, but I don't over-use it.. I save it for when she's taking a high risk. It works for me but I have to keep my powder dry.
I'm very interested in this. I'm always searching for ways to help people understand that their objective should be that no one gets hurt on their trip.