According to the eNotes study guide for William Inge's "Bus Stop," it is a three-act play. If you click on the reference link below it will take you to the eNotes site which provides abundant information about the play as well as about William Inge. According to the study guide, "Bus Stop" was based on an earlier play by Inge which is titled "People in the Wind." If you click on the side-heading titled Summary in the study guide, you can read a complete summary of the play broken down by the three acts. You might want to consider doing a production of "People in the Wind."