87.—(1) It is the duty of a safety critical worker and is deemed to be a term of his or her contract of employment or contract of services (whether made before or after the passing of this Act) with a F114[railway organisation] or with a person who has a contract of services with a F114[railway organisation]—

(a) not to perform a safety critical task while being unfit,

(b) not to make himself or herself available to perform a safety critical task by attending at work while being unfit,

(c) not to do anything that is an offence under section 97, and

(d) to comply with the F114[railway organisation]’s code of conduct and sampling procedures.

(2) It is the duty of a F114[railway organisation] to take reasonable steps to ensure that a safety critical worker complies with his or her duties under subsection (1).

(3) In this section, “unfit” has the meaning assigned to it in section 97.