Simulation Guidance for Calibration of Freeway Lane Closure Capacity

Abstract

This study provides a methodology for calibrating freeway work zone capacity in a microsimulation environment and guidance for replicating field-observed freeway work zone capacity through simulation. From 81 field observations at 12 U.S. work zone sites, 90 work zone sites from literature archival sources, and a macroscopic capacity model developed in NCHRP Project 03-107, the authors show how to replicate field-observed or forecast capacity in the Vissim simulation tool under various scenarios of freeway work zone lane closure. With guidance from an in-depth literature review, key car-following and lane-changing parameters are proposed as a result of the calibration effort and extensive sensitivity tests of numerous combinations of parameter values. Lane configuration specific guidance is provided for two key car-following parameters in Vissim, cc1 and cc2. During the process of developing the guidance, every tested capacity scenario was verified by using a lane use volume balance that was obtained upstream of the lane closure point in order to replicate realistic freeway work zone conditions. The calibration methodology as well as default parameter guidance developed through this research are useful to practitioners who wish to model freeway work zone impacts accurately through microsimulation.