A method and apparatus for displaying a representation of a traffic roundabout having a central island surrounded by a circulatory lane is disclosed. The method involves receiving an operator selection of a design vehicle that is expected to use the roundabout, and receiving operator input of a design dimension for the roundabout, the design dimension defining a size of one of the central island and an outer perimeter of the circulatory lane. The method also involves generating a circulatory path of the design vehicle traveling within the design dimension along the circulatory lane, and generating vehicle extent locations associated with passage of the design vehicle along the circulatory path. The method also involves using the vehicle extent locations to compute a circulatory lane width, and generating display signals for causing the display to display an image representing the roundabout.