(a) the said signals are so placed that they face the stream of traffic to which they are intended to convey respectively the warnings, information, requirements, restrictions or prohibitions prescribed by the Regulations;
(b) where the road on or near which the said signals are proposed to be placed is a motorway, a trunk road, or, outside Greater London, a principal road or a road which is subject to a speed limit of 40 miles per hour or more, the site for the said signals (except as provided by sub-paragraph (2) of this paragraph) shall have first been approved in writing by or on behalf of the Secretary of State, after consideration of such plans for the sites, such particulars of the apparatus to be used in connection with the signals (including particulars of the content of all sequences of instructions stored in or executable by that apparatus) and such information as to the volume and character of the traffic affected as he may require;
(c) where the road on or near which the said signals (except as provided by sub- paragraph (2) of this paragraph) are proposed to be placed is any other road than a road of the kind specified in sub-paragraph (i) (b) of this paragraph, there shall have first been approved in writing by or on behalf of the Secretary of State—
(i) the type of apparatus to be used in connection with those signals and the content of all sequences of instructions stored in or executable by that apparatus, and
(ii) if the said signals are signals prescribed by Regulation 31(2) of the Regulations or such signals as varied by Regulation 32 thereof, or are signals prescribed by Regulation 36 of the Regulations, then in addition and without prejudice to the foregoing requirements of sub- paragraph (1)(c)(i) of this paragraph, the number and disposition of the said signals to be erected to control traffic using the said road at any one junction of that road with one or more roads not being roads of the kinds mentioned in sub-paragraph (1)(b) of this paragraph; and
(d) where portable light signals of the type prescribed by Regulation 33 of the Regulations are proposed to be used on or after 1st January 1976, the type of apparatus by means of which those signals are capable of complying with Regulation 31(2)(g) of the Regulations shall have first been approved in writing by or on behalf of the Secretary of State.
(2) Sub-paragraph (1)(b) and (c) of this paragraph shall not apply—
(a) in the case of such light signals as are prescribed by Regulation 31(4) of the Regulations, being signals provided at or near to any level crossing in pursuance of an Order made by the Secretary of State under section 66 of the British Transport Commission Act 1957[1] (which empowers the Secretary of State to authorise special arrangements at public level crossings) or of any Order so made under section 124 of the Transport Act 1968[2] (British Railways Board's obligations at level crossings with roads other than public carriage roads);
(b) in the case of such portable light signals as are prescribed by Regulation 33 of the Regulations.
(3) The light signals prescribed by Regulation 31(2) and (4) of the Regulations or those light signals as varied in accordance with Regulation 32 thereof shall not be used unless used in conjunction with the road marking shown in diagram 1001 except that this sub-paragraph shall not apply while works which necessitate the temporary removal of that road marking are being executed on a road in the vicinity of the place where the said light signals are erected.
(4) The containers enclosing the lamps of each of the kinds of light signals
