It shall be the duty of the local planning authority to institute a survey of their area, in so far as they have not already done so, examining the matters which may be expected to affect the development of that area or the planning of its development and in any event to keep all such matters under review.
Notwithstanding that the local planning authority have carried out their duty under subsection (1) of this section, the authority may, if they think fit, and shall, if directed to do so by the Secretary of State, institute a fresh survey of their area examining the matters mentioned in that subsection.
Without prejudice to the generality of the preceding provisions of this section, the matters to be examined and kept under review thereunder shall include the following, that is to say—
(a) the principal physical and economic characteristics of the area of the authority (including the principal purposes for which land is used) and, so far as they may be expected to affect that area, of any neighbouring areas;
(b) the size, composition and distribution of the population of that area (whether resident or otherwise);
(c) without prejudice to paragraph (a) of this subsection, the communications, transport system and traffic of that area and, so far as they may be expected to affect that area, of any neighbouring areas;
(d) any considerations not mentioned in any of the preceding paragraphs which may be expected to affect any matters so mentioned;
(e) such other matters as may be prescribed or as the Secretary of State may in a particular case direct;
(f) any changes already projected in any of the matters mentioned in any of the preceding paragraphs and the effect which those changes are likely to have on the development of that area or the planning of such development.
A local planning authority shall, for the purpose of discharging their functions under this section of examining and keeping under review any matters relating to the area of another such authority, consult with that other authority about those matters.
Subsection (1) of this section shall, as respects any period during which this section is in operation in part only of the area of a local planning authority, be construed as requiring a local planning authority to institute a survey of that part of that area and to keep under review matters affecting only that part of that area ; and subsection (2) of this section shall, whether or not this section is in operation in the whole of such an area, have effect as if the power thereby conferred included power for a local planning authority to institute, and for the Secretary of State to direct them to institute, a fresh survey of part only of their area; and references in subsection (3) of this section to the area of a local planning authority or any neighbouring areas shall be construed accordingly.