17.—(1) Where the safety requirements specify a structural requirement that can only be satisfied by means of a technical solution that is not possible to achieve, or only achievable at disproportionate cost, the Tunnel Manager may apply to the administrative authority for authority to use a risk reduction measure.
(2) Where the same body is both the administrative authority and the Tunnel Manager, an application referred to in paragraph (1) shall be considered by a person who is functionally independent from the persons acting on behalf of the body in its capacity as Tunnel Manager.
(3) The administrative authority shall not permit the use of a risk reduction measure unless a risk analysis demonstrates that the measure will result in equivalent or improved protection for users of the road tunnel, compared to the relevant structural requirement in the safety requirements.
(4) Where the administrative authority permits the use of a risk reduction measure it shall—
(a)specify a timetable for implementation of that measure; and
(b)notify the Secretary of State of the risk reduction measure to be used and the structural requirement that it replaces.
(5) This Regulation does not apply in relation to a road tunnel that is at the design stage but the design of which had not been approved by the technical approval authority by 1st May 2006.