The study responded to trucking industry concerns that certain roundabouts unduly delay traffic. For a nuanced evaluation, we:

• Identified GPS Events: Isolated vehicle movements around and through the Sisters and Fyfe roundabouts, filtering for relevant turning events and path segments.
• Developed a Traversal-Time Model: Estimated how long vehicles took to circulate each roundabout, including circular speed dynamics. We used imputation techniques to fill gaps where GPS data was incomplete.
• Integrated GPS with On‑Site Surveys: Ground surveys were used to validate GPS-derived metrics, ensuring robustness and credibility in the analysis.
• Compiled a Research Report for ODOT: The study culminated in a formal paper presented to Oregon Department of Transportation, offering unbiased evidence on roundabout delay characteristics with particular emphasis on heavy vehicles.

Impact:

• Delivered clear, quantitative insights into how trucks and other vehicles move through critical roundabout locations, helping challenge or confirm stakeholder perceptions.
• Informed ODOT’s operational assessments and potential design refinements.
• Demonstrated the value of integrating GPS and field observation methods in evaluating traffic control infrastructure.

Additionally, this work complements broader research like OSU’s thesis on roundabout safety performance (i.e., developing safety performance functions for four-leg single-lane roundabouts) Wikipedia+15ir.library.oregonstate.edu+15SCIRP+15ROSA P and ODOT’s SPF-based models for roundabout safety evaluation Oregon+3Oregon+3Oregon+3.

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