The governing body of any county or town may enter into an agreement with the Commissioner of Highways allowing the county or town to install and maintain, at locations specified in such agreement, signs alerting motorists that children may be at play nearby. The cost of the signs and their installation shall be paid by the county or town. The provisions of this section shall not apply to any county that has withdrawn its roads from the secondary state highway system under the provisions of § 11 of Chapter 415 of the Acts of Assembly of 1932 and has not elected to return.