Calibration of work zone impact analysis software for Missouri.

Edara, Praveen; Sun, Carlos; Zhu, Zhongyuan · 2013 · ROSA P / Mid-America Transportation Center

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Summary

This study addresses the need for accurate traffic impact assessments in Missouri work zones by calibrating two software tools: the WZ Spreadsheet and the VISSIM microscopic simulation program. Motivated by the widespread adoption of these tools following a previous phase of research, the authors sought to refine their parameters using empirical field data to improve the estimation of travel delay, queue length, and road user costs. The research focused on calibrating the models for specific work zone configurations, particularly single-lane closures on three-lane roadways, to ensure the software accurately reflects local traffic conditions. The methodology involved collecting field data from two distinct work zones in Missouri: a long-term construction zone on I-44 near St. Louis and a short-term maintenance zone on I-70. Both sites featured one lane closed out of three. Data collection utilized permanent and temporary traffic sensors to record hourly volumes, speeds, and occupancies, as well as Bluetooth sensors for travel time analysis. The calibration process employed a three-step framework: identifying performance measures (delay or queue length), acquiring and processing input data, and using least squares error estimation to determine the parameter values that minimized the difference between simulated and observed outcomes. For the WZ Spreadsheet, the primary calibration parameter was work zone capacity. For VISSIM, the calibration focused on driving behavior parameters, specifically CC1, CC2, and the Safety Reduction Factor (SRF), which influence car-following and lane-changing behaviors. The results indicated that the calibrated capacity values for the two software programs were nearly identical: 1,575 veh/hr/ln for the WZ Spreadsheet and 1,514 veh/hr/ln for VISSIM. The study further compared calibration strategies based on minimizing delay errors versus minimizing queue length errors. It found that calibration based on delay or travel time exhibited superior overall performance, producing acceptable estimates for both delay and queue length. In contrast, calibration based solely on queue length resulted in significantly higher errors in delay estimates. For the VISSIM model, specific driving behavior parameters were computed to match the observed field capacities. Validation of the WZ Spreadsheet using independent data from the same day of the week confirmed that the calibrated capacity values produced delay and queue estimates closely aligned with actual field observations. The significance of this research lies in providing validated, state-specific parameters for traffic impact analysis software, thereby enhancing the reliability of work zone planning and scheduling in Missouri. The findings recommend that future calibrations prioritize delay-based metrics over queue-length-based metrics for better accuracy. The authors conclude that while the current calibration is robust for single-lane closures on three-lane segments, additional case studies are necessary to extend these calibrated parameters to other configurations, such as one-lane closures on two-lane segments or two-lane closures on three-lane segments, to broaden the applicability of the models.

Key finding

Calibration based on delay or travel time exhibited better overall performance than calibration based on queue length, with optimal capacity values determined to be 1,575 veh/hr/ln for the WZ Spreadsheet and 1,514 veh/hr/ln for VISSIM.

Methodology

field_study

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• work zones