Suggested improvements for modeling heavy truck traversal at roundabouts using PTV VISSIM based on gap acceptance behavior calibrated to field observations

• Conflict area models consistently overestimate critical gap requirements by 7–8 s. • Observed heavy truck fleet and priority rules produced representative gap profiles. • Priority rules for heavy trucks at roundabouts yielded better calibration. • Fleets composed of observed heavy truck classifications yield better calibration. Heavy trucks are vital to the movement of goods and services and their importance to the overall transportation system gives reason to evaluate improved methods for modeling their presence on the roadway. The present study derived recommendations for modeling heavy truck maneuvers through roundabouts within the VISSIM microsimulation platform to better align simulated flow with field observations, and followed protocols and standards set by the Oregon Department of Transportation. The impact of two different variables was evaluated and required composition of four models: method of unsignalized control (priority rules, conflict areas) and truck fleet composition (default fleet, observed fleet). The findings revealed that priority rules better modeled heavy truck behavior through roundabouts with gap acceptance tendencies, vehicular speed, and volumetric loadings most closely aligning with field observed values. Furthermore, use of the observed heavy truck fleet and priority rules resulted in representative gap rejection tendencies and critical gap lengths of 6.2 s. Conflict area models were found to consistently overestimate the critical gap requirements resulting in estimates between 7.0 and 8.0 s. Practical implications of this work indicate that modeling heavy truck movements at roundabouts within VISSIM can be improved by using priority rules and generating a fleet composed of representative truck classifications at the location of interest. Additionally, using existing trailer designs and connectors contained within VISSIM, larger vehicle configurations can be created to generate vehicle models as needed. These findings should be considered when modeling roundabouts in VISSIM and considering the impact of high heavy truck flows.