Every safety-critical industry has its own legislation and standards which safety engineers have to consider in their demonstration that a system is safe. Often these standards overlap and conflict and they inevitably become out of date as technology and understanding advance. In addition, there are always trade-offs to consider between safety, environment, performance (and sometimes security). Choosing an approach for a project involves selecting standards and resolving these conflicts in a way which is acceptable to each of the parties whose approval the project needs to secure. This paper examines some of the challenges, drawing on the authors’ experience across multiple industry sectors. The paper then derives some principles for making suitable, informed choices at the outset of a project and for monitoring those choices as the project proceeds.