The department may make recommendations to such political units concerning the metropolitan district. In so doing it shall have regard for:
(a)
The present conditions and future needs and growth of the district.
(b)
The distribution and relative location of all streets and railways, waterways, and other means of public travel and business communication.
(c)
The distribution and relative locations of all public buildings, public grounds, and open spaces devoted to the public
use.
(d)
The planning and laying out for urban uses of private grounds brought into the market from time to time.