Susan is a small narrow gauge engine who's a part of The Crotoonian Railway Police Department. Her job is to patrol the narrow  gauge lines of The Crotoonian Hills Narrow Gauge Railway, looking to apprehend anyone who breaks the law and take them to the Railway Impound Lot, where engines who break the law are kept until released. She has no original voice, as she's an O.C. However, though she's a kind engine, her voice should sound like an officer of the law. This role has been casted to : Yilin Zhou