VISSIM Calibration for Urban Freeways, 2015

(2015) VISSIM Calibration for Urban Freeways, 2015. Transportation, Department of


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In urban areas, interchange spacing and the adequacy of design for weaving, merge, and diverge areas can significantly influence available capacity. Traffic microsimulation tools allow detailed analyses of these critical areas in complex locations that often yield results that differ from the generalized approach of the Highway Capacity Manual. In order to obtain valid results, various inputs should be calibrated to local conditions. This project investigated basic calibration factors for the simulation of traffic conditions within an urban freeway merge/diverge environment. By collecting and analyzing urban freeway traffic data from multiple sources, specific Iowa-based calibration factors for use in VISSIM were developed. In particular, a repeatable methodology for collecting standstill distance and headway/time gap data on urban freeways was applied to locations throughout the state of Iowa. This collection process relies on the manual processing of video for standstill distances and individual vehicle data from radar detectors to measure the headways/time gaps. By comparing the data collected from different locations, it was found that standstill distances vary by location and lead-follow vehicle types. Headways and time gaps were found to be consistent within the same driver population and across different driver populations when the conditions were similar. Both standstill distance and headway/time gap were found to follow fairly dispersed and skewed distributions. Therefore, it is recommended that microsimulation models be modified to include the option for standstill distance and headway/time gap to follow distributions as well as be set separately for different vehicle classes. In addition, for the driving behavior parameters that cannot be easily collected, a sensitivity analysis was conducted to examine the impact of these parameters on the capacity of the facility. The sensitivity analysis results can be used as a reference to manually adjust parameters to match the simulation results to the observed traffic conditions. A well-calibrated microsimulation model can enable a higher level of fidelity in modeling traffic behavior and serve to improve decision making in balancing need with investment.

Item Type: Departmental Report
Keywords: driving behavior, fleet composition, microsimulation model, standstill distance, urban freeway capacity, VISSIM calibration, Freeways, Calibration, Highway capacity, Headways, Traffic congestion
Subjects: Transportation
Transportation > Traffic Management
Transportation > Roads and highways
Transportation > Research
Transportation > Design and Construction
Transportation > Data and Information Technology
Transportation > Drivers
ID Code: 22394
Deposited By: Iowa DOT Library
Deposited On: 06 Jul 2016 13:23
Last Modified: 06 Jul 2016 13:23