We are designing a feedback system to encourage more fuel-efficient driving habits among school-bus drivers. We chose to design for the school bus because as one of the largest public transport systems in the U.S., it is a major contributor to the country's total fuel consumption and pollutant emissions. Our design uses persuasive technology to discourage excessive idling and aggressive driving by providing real-time in-vehicle feedback for self-monitoring. Keywords Persuasive Technology, Captology, Automobile Interfaces, Automobile Cockpit Design, Designing for Eco-Driving, Mission-Critical Systems ACM Classification Keywords H5.m. Information interfaces and presentation (e.g., HCI): Miscellaneous, Ergonomics, User-centered design