Use of Microsimulation to Assess HCM2010 for Oversaturated Conditions

Current Highway Capacity Manual (HCM) 2010 methodology for freeway operations contains procedures for calculating traffic performance measures both for undersaturated and oversaturated flow conditions. However, one of the limitations regarding oversaturated freeway segments is that the HCM procedures have not been extensively calibrated based on field observations on U.S. freeways. This study validates the HCM2010 methodology for oversaturated freeway weaving segment by comparing speed and density obtained from HCM procedure to those obtained from a microsimulation model. A VISSIM model is extensively calibrated and validated based on NGSIM field data for the US 101 Highway. An abundance of the NGSIM data is utilized to calibrate and validate the VISSIM model. The results show that HCM methodology has significant limitations and while in some cases it can reproduce density correctly, the study finds that speeds estimated by the HCM methodology significantly differ from those observed in the field.