The document discusses a research project that uses a smartphone app to collect subjective travel experience data from individuals. The app will provide feedback to users about their own experiences as well as those of others. The researchers aim to see if these interventions can change travel behaviors and reduce emissions. They will draw on theories from behavioral economics, psychology, and technology acceptance. An important goal is to pilot and refine the app to make it more usable and understand its impact on travel choices over multiple trials involving both strangers and friends.