ABSTRACT
Before the theory of designed experimentation is discussed, it is worthwhile to compare and contrast the two primary methods of obtaining data that transportation engineers will be exposed to during their careers. In transportation engineering the most common methodology is direct observation. For example, a transportation analyst may wish to study gap acceptance during the permitted le turn phases at unsignalized intersections. e analyst would choose one or more representative unsignalized intersections and observe the attributes of the permitted le turning
movements (e.g., type of vehicle, size of gaps chosen, speed of oncoming vehicles, size of gaps not chosen, number of lanes, etc.). Based on this information, a gap acceptance model could then be developed.
