When is a transition included in a Standard Instrument Departure (SID) assigned?

A transition is included in a Standard Instrument Departure (SID) when it is required to ensure a safe and efficient departure from an airport. The primary purpose of a SID is to provide clear, standardized procedures for aircraft climbs immediately after takeoff, which helps in managing air traffic and enhances safety.

Including a transition in the SID is essential when the aircraft needs to follow specific routing to navigate effectively through controlled airspace or to join the en-route structure. This might involve certain fixes or waypoints that help the flight remain on track towards its intended route. In circumstances where the SID specifies a transition as part of the procedure, it is necessary for compliance with air traffic management requirements and to provide separation from other aircraft.

Other options, such as if not necessary, cleared by the controller, or if the pilot requests, do not capture the mandatory nature of the requirement for transitions in SIDs. Instead, these options imply conditions that may not necessarily apply when following standard departure procedures.