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As congestion worsens, the importance of rigorous methodologies to estimate travel-time reliability increases. Exploiting fine-granularity transit GPS data, this research proposes a novel method to estimate travel-time percentiles and confidence intervals. Novel transit reliability measures based on travel-time percentiles are proposed to identify and rank low-performance hotspots; the proposed reliability measures can be utilized to distinguish peak-hour low performance from whole-day low performance. As a case study, the methodology is applied to a bus transit corridor in Portland, Oregon. Time-space speed profiles, heatmaps, and visualizations are employed to highlight sections and intersections with high travel-time variability and transit low performance. Segment and intersection travel-time reliability are contrasted against analytical delay formulas at intersections with positive results. If bus stop delays are removed, this methodology can also be applied to estimate regular traffic travel-time variability.

Biographical Information

Travis Glick is currently a graduate teaching and research assistant in the Maseeh College of Engineering and Computer Science at Portland State University. He started researching Portland's public transit system in the summer of 2014, this ongoing research has resulted in multiple publications and lectern presentations at the TRB 94th, 95th, and 96th annual meetings. Following the completion of his undergraduate honors thesis at PSU in 2015, he received a Bachelor of Science degree in civil engineering and is now pursuing a Master of Science degree in civil engineering at PSU. In his free time, Travis loves to hike, sing, play piano and the flute, and read about everything from modern and ancient history to science fiction and fantasy. Most of all, he loves to spend time with his family, friends, and cats, Castor and Pollux.


Travel time (Traffic engineering), Traffic congestion -- Measurement, Tri-County Metropolitan Transportation District of Oregon


Transportation | Transportation Engineering | Urban Studies and Planning

Persistent Identifier

Estimating Reliability Indices and Confidence Intervals for Transit and Traffic at the Corridor Level