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Temporal Aggregation Effects on ITS Data Applications

Temporal Aggregation Effects on ITS Data Applications. Sustainable transportation performance measures. Alex Bigazzi Portland State University. Objective. Effects of time-aggregating data on sustainability performance measures. Data Source. ~2 miles of M4 in London

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Temporal Aggregation Effects on ITS Data Applications

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  1. Temporal Aggregation Effects on ITS Data Applications Sustainable transportation performance measures Alex Bigazzi Portland State University ITS Data Aggregation Effects – Alex Bigazzi

  2. Objective • Effects of time-aggregating data on sustainability performance measures ITS Data Aggregation Effects – Alex Bigazzi

  3. Data Source • ~2 miles of M4 in London • Individual arrival times and speeds • 24hr data over 5 weeks (1998) • 500 meter spacing ITS Data Aggregation Effects – Alex Bigazzi

  4. and effects on related measures Speed Distributions ITS Data Aggregation Effects – Alex Bigazzi

  5. Speed Consolidation 11-16-98, station 172 ITS Data Aggregation Effects – Alex Bigazzi

  6. ITS Data Aggregation Effects – Alex Bigazzi

  7. Travel Time ITS Data Aggregation Effects – Alex Bigazzi

  8. Endpoint method of travel time estimation ITS Data Aggregation Effects – Alex Bigazzi

  9. Sampling Error – neglected here x Sampling Error Detector Speed-Estimated Trajectory True Trajectory Travel Detector t ITS Data Aggregation Effects – Alex Bigazzi

  10. Grouped Speed Error x Grouped Speed Error Detector Individual Speed Trajectories Travel Average Speed Trajectory Detector t ITS Data Aggregation Effects – Alex Bigazzi

  11. Harmonic Mean Speed (mph) Arithmetic Mean Speed (mph) 1 week of speeds ITS Data Aggregation Effects – Alex Bigazzi

  12. Estimate space mean speed from time mean speed Rearranging: Ref: Lindveld and Thijs ITS Data Aggregation Effects – Alex Bigazzi

  13. 1min data (one day, one station) CV CV ITS Data Aggregation Effects – Alex Bigazzi

  14. ITS Data Aggregation Effects – Alex Bigazzi

  15. Combined effects of speed distribution and travel time errors Delay ITS Data Aggregation Effects – Alex Bigazzi

  16. 80 Speed FFS 60 40 20 0 16:00 20:00 4:00 8:00 12:00 ITS Data Aggregation Effects – Alex Bigazzi

  17. One week of delay (all stations) Disaggregate ITS Data Aggregation Effects – Alex Bigazzi

  18. ITS Data Aggregation Effects – Alex Bigazzi

  19. Conclusions • With respect to disaggregate data: • Speed consolidation • Underestimate emissions, fuel • Travel time • TMS underestimates TT and delay • Est. SMS from TMS and variance ITS Data Aggregation Effects – Alex Bigazzi

  20. Considerations • Costs of data management • Future uses for data • Missing or bad data • Other summary stats • Variance • Harmonic mean • Median ITS Data Aggregation Effects – Alex Bigazzi

  21. Thank you! Questions? ? ? ? Acknowledgements Dr. Robert Bertini, Helene Siri, Stuart Beale, Tim Rees, and OTREC ITS Data Aggregation Effects – Alex Bigazzi

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