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

2. Objective 2ITS Data Aggregation Effects – Alex Bigazzi Effects of time-aggregating data on sustainability performance measures Emissions Fuel Consumption Speed distributions Delay Travel time estimates

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

4. SPEED DISTRIBUTIONS and effects on related measures 4ITS Data Aggregation Effects – Alex Bigazzi

5. Speed Distribution Consolidation 5ITS Data Aggregation Effects – Alex Bigazzi

6. Speed Consolidation 6ITS Data Aggregation Effects – Alex Bigazzi 11-16-98, station 172

7. 7ITS Data Aggregation Effects – Alex Bigazzi Speed Consolidation Emissions Fuel Consumption Safety

8. TRAVEL TIME 8ITS Data Aggregation Effects – Alex Bigazzi

9. 9 Endpoint method of travel time estimation

10. 10ITS Data Aggregation Effects – Alex Bigazzi x t Travel Sampling Error True Trajectory Speed-Estimated Trajectory Detector Sampling Error – neglected here

11. 11ITS Data Aggregation Effects – Alex Bigazzi x t Travel Grouped Speed Error Individual Speed Trajectories Average Speed Trajectory Detector Grouped Speed Error

12. 12ITS Data Aggregation Effects – Alex Bigazzi 1 week of speeds Arithmetic Mean Speed (mph) Harmonic Mean Speed (mph)

13. Estimate space mean speed from time mean speed Rearranging: 13ITS Data Aggregation Effects – Alex Bigazzi Ref: Lindveld and Thijs

14. 1min data (one day, one station) 14ITS Data Aggregation Effects – Alex Bigazzi CV

15. 15ITS Data Aggregation Effects – Alex Bigazzi

16. DELAY Combined effects of speed distribution and travel time errors 16ITS Data Aggregation Effects – Alex Bigazzi

17. 17ITS Data Aggregation Effects – Alex Bigazzi 80 60 40 20 0 Speed 4:008:0012:00 16:00 20:00 FFS

18. One week of delay (all stations) 18ITS Data Aggregation Effects – Alex Bigazzi Disaggregate

19. 5 minute aggregation 19ITS Data Aggregation Effects – Alex Bigazzi

20. 20ITS Data Aggregation Effects – Alex Bigazzi

21. Conclusions 21ITS Data Aggregation Effects – Alex Bigazzi With respect to disaggregate data: Speed consolidation -Underestimate emissions, fuel Travel time -TMS underestimates TT and delay -Est. SMS from TMS and variance

22. Considerations  Costs of data management  Future uses for data  Missing or bad data  Other summary stats o Variance o Harmonic mean o Median 22ITS Data Aggregation Effects – Alex Bigazzi

23. Thank you! 23ITS Data Aggregation Effects – Alex Bigazzi Acknowledgements Dr. Robert Bertini, Helene Siri, Stuart Beale, Tim Rees, and OTREC Questions?