In hazardous liquids and gas control rooms, controllers rely on their Supervisory Control and Data Acquisition (SCADA) Human Machine Interface (HMI) as their main tool. A ÒHighly EffectiveÓ HMI is one where planning and design goes above and beyond recommended practices to maximize controller awareness and minimize errors. Controllers are the target user group for the SCADA HMI and it must it be designed around their needs in the control room. It is by applying a structured process and listening to controllers that we can provide them with highly effective HMIs. This book provides guidance for the HMI design process, and high-level direction for developing a highly effective HMI. It is not meant to deliver step-by-step instructions. The intention is to help guide and develop a strategy and lay the groundwork to get the HMI development process and required resources established.