Upon the adoption of a resolution therefor by a majority vote of the members elect of the township board of any township, and the subsequent approval by a majority of the township electors voting thereon, the provisions of this act shall apply in any township now or hereafter having a population of 60,000 or more. The township board may submit the question at any regular election or special election called for some other purpose, and shall submit the question at any such election held not less than 60 days after the filing with the township clerk of petitions for such submission signed by at least 4% of the registered electors of the township.