Highway capacity through vissim calibrated for mixed traffic conditions

Abstract

The present study demonstrates applicability of VISSIM software to determine capacity of multilane highways under mixed traffic flow conditions. Traffic flow data collected on a section of four-lane divided highway are used to develop the speed-flow curve. The same set of field data is used in VISSIM and simulated speed-flow curve is compared with field curve. It was found that VISSIM in its original form overestimates both speed and capacity of the highway. Driver behaviour parameters CC0 and CC1 are first determined for homogeneous traffic conditions having only one of the four types of vehicles in the stream and then results are aggregated to get the values of these parameters for a mixed traffic stream. Further analysis of field data with calibrated values of CC0 and CC1 indicated a good match between field and simulated capacity. The procedure is shown to work on another section of four-lane divided highway with paved shoulders, where simulated capacity was 5329 pcu/hr against the field capacity of 5277 pcu/hr.