Before a street railway is constructed on any street less than sixty feet in width, with a roadway of thirty-five feet or under, the legislative authority of a municipal corporation shall provide that the crown of the street shall be made a nearly flat uniform curve from curb to curb, without ditch gutters, and in such manner as to give wheeled vehicles the full use of the roadway up to the face of the curb. When the tracks of two street railways, or of a street railway and a railroad, cross each other at a convenient grade on a street, such crossings shall be made with crossing-frogs of the most approved pattern and materials, and shall be kept in repair at the joint expense of the companies owning such tracks.