Concrete sidewalks having a minimum width of four (4) feet and a minimum thickness of four (4) inches may be required to be installed on both sides of all new streets in subdivisions where the density exceeds three dwelling units per net acre, and in all commercial developments. The Village Planning Commission may require for safety purposes a sidewalk along only one side of any new street where the net residential density is less than three (3) dwelling units per net acre. All sidewalks shall be extended to connect with existing walks or to the boundaries of the subdivision if walks are not accessible.