People do or don’t do things depending on three variables: motivation to do it, the ability to do it, and the prompt to do it.

• Motivation could be lacking in some cases. People need to understand the purpose of turn signals. However, I don’t think there’s an anti-turn signal discourse going around. At least as far as I know.
• I don’t think it’s ability, because activating turn signals is relatively easy for most people.
• I think prompts could also be lacking.

How do we change this?

The Behavior Design answer would be something like this: We need to patiently and kindly train people to recognize prompts to the turn signals. “When you get to the corner, put your left hand on the turn-signal control and move it up. Then turn right.” We also need to celebrate it the instant they do it. “Perfect”. Of course, you need to have a good relationship with whomever you’re doing this with.

Now, that is not the only solution; there are many. We might have one solution if we zoom in on one person. We might have another solution if we zoom out to a whole city or country.

In any case, if we want to solve the problem with Behavior Design, you could check out Tiny Habits.