Relationships Between Occupancy and Density Reflecting Average Vehicle Lengths

The linearity of the occupancy-density relationship is investigated by studying the relationship mathematically across a wide range of traffic situations as well as by plotting values of both variables on the occupancy-density diagram. The literature does not show general agreement on the linearity of the relationship. The relationship is shown to be practically linear because the nonlinear factor mathematically derived does not have noticeable effects on the linearity of the relationship. However, the plot of both variables on the occupancy-density diagram shows that the relationship is influenced by varying average vehicle lengths and can be interpreted as being either linear or nonlinear. The proportion of long vehicles (trucks) is tested empirically and is shown to have large effects on the linearity of the relationship.