Gap maintaining behavior significantly affects the traffic flow modeling under heterogeneous traffic
conditions. The clearance between two adjacent moving vehicles varies depending on several traffic
conditions. From the data collected on the gap maintaining behavior it has been observed that vehicles
maintain different gaps when travelling under different traffic conditions and this is also influenced by
lateral position of the vehicle. Mallikarjuna (2007) has found that this variable gap maintaining behavior
can be explained using a macroscopic traffic characteristic called area occupancy. In this study, these
relationships would be used in deciding the cell width which is the basic input for cellular automata (CA)
based heterogeneous traffic flow models. It is proposed that the dominant vehicle in the traffic stream, its
lateral position, and lateral gaps on either side are the governing factors in deciding the cell width. Cell
width has been finalized based on this input and it is found to be varying when area occupancy is varying
from 3 to 15%
