This document provides guidance on railway project planning for decision making. This document explores the key points of railway project planning, based upon the principles of ISO 21500, by incorporating characteristics specific to railway projects. This document covers: — the characteristics of railway projects; — stakeholders and their needs/interests; — conditions; — the definition of each process in a railway project; — key points of planning process; — correlation and causality among principal factors to be considered. This document can be used by any type of organization, including public, private or community organizations, and be applied to any type of railway project, irrespective of its complexity, size, duration, etc. However, this document provides neither detailed requirements nor specific processes for: — certification; — deriving a unique solution (specification for particular systems/products); — decision making itself. Topics pertaining to general projects are addressed only within the context of railway projects.