We all have somewhere to be. Increasingly, we're surrounded by others as we travel, mass transportation or otherwise. You pass by just as many people on your bike as you do in a bus.
By plane, by train, by automobile...
Long before Alfred Hitchcock and Paula Hawkins made people-watching terrifying, we did it. We've envied others' style, imagined details of their lives, caught inspiration for a new project, wished we were going where they were or pitied them for not going where we were. Why do we think we can learn so much from appearances?
Few other situations provide this unique combination of motion and confinement. You're moving through space, but when the seat belt light is on, you had better be in your seat. It's what makes the long car ride the perfect opportunity to "let things happen." All this time alone with one's thoughts, yet trapped in the company of a set group of strangers is also what makes it possible for people to see terror in math equations.
Where will your story take your characters this week?
If this prompt isn't providing much inspiration today, check out my other prompts here.