They are required to perform their normal daily period of duty (or shift) in more than one tour of duty

They are recalled to duty between two tours of duty (or two shifts) and travel to and from their home between tours or as the case may be, in consequence of his recall, or

They are held in reserve within the meaning of Paragraph 11 of Annex U, and are required to travel other than during the member’s normal daily period of duty or shift. Annex U, Paragraph 11, states that a member is held in reserve if the member is serving away from his normal place of duty and is required to stay in a particular, specified place overnight rather than being allowed to return home by reason of the need to be ready for immediate deployment. A member is not held in reserve if serving away from his normal place of duty only by reason of being on a training course or carrying out routine enquiries.