Neb. Rev. Stat. § 18-618

After the passage and publication of a resolution as provided in section 18-617 , a city or village shall have authority to enter into contracts and agreements with any railroad company or companies over or under whose railroad a viaduct or subway is to be constructed providing for the construction and maintenance of such viaduct or subway and for the apportionment of the costs thereof. Such agreement or contract shall not be effective nor shall any work be commenced until after such matter is submitted to a vote of the electors as provided in section 18-623 .