In order to lessen congestion on the streets and to facilitate adequate provisions for community utilities and facilities such as transportation, any city or village which has a comprehensive zoning ordinance is authorized to require that no building or structure shall be erected or enlarged upon any lot in any zoning district unless the half of the street adjacent to such lot has been dedicated to its comprehensive plan width. The maximum area of land required to be so dedicated shall not exceed twenty-five percent of the area of any such lot and the dedication shall not reduce such a lot below a width of fifty feet or an area of five thousand square feet. Any owner of such a lot may submit an application for a variance and the city or village shall provide a procedure for such application to prevent unreasonable hardship under the facts of each case. The authority granted in this section is in addition to the authority of the city or village to require dedication of right-of-way as a condition of subdivision approval.