Designing the user interface for a car rental mobile app involves creating a seamless and user-friendly experience. Prioritize a simple and intuitive booking process, allowing users to easily select vehicle preferences, pick-up/drop-off locations, and rental durations. Implement clear visuals and straightforward navigation to enhance the overall usability. Include features such as real-time availability updates, pricing transparency, and secure payment options to build trust. Consider incorporating a user-friendly dashboard for managing reservations, viewing rental history, and accessing support services, ensuring a convenient and enjoyable experience for users renting cars through the app.