How to focus on the relationship if the two characters are strangers?

I'm a beginner improviser and I would love learn how to make a scene about two strangers more about the relationship. For example, I started a scene where I acted as the police officer who pulled over my scene partner for running a red light. Quickly I realized I had no idea how to make it about the two of us, since we had no prior relationship. What are some suggestions to turn this scene towards the relationship between these two strangers?