1. Using Ground Truth Geospatial Data to Validate Advanced Traveler Information Systems Freeway Travel Time Messages
CTS Transportation Seminar Series, January 13, 2006
Aaron Breakstone
Master of Urban and Regional Planning Candidate
Portland State University
Chris Monsere, Ph.D., P.E.
Research Assistant Professor
Robert L. Bertini, Ph.D., P.E.
Associate Professor
Director, Center for Transportation Studies

2. Outline Project Overview Summary of Test Area Experimental Design
Data Collection
Data Comparison
Results
Next Steps

3. Outline Project Overview Summary of Test Area Experimental Design
Data Collection
Data Comparison
Results
Next Steps

4. Project Overview Goals
Evaluate Oregon Department of Transportation (ODOT)’s travel time estimating and reporting capabilities
Identify locations where additional detectors might improve estimates

5. Project Overview
ODOT Region 1 Traffic Management Operations Center (TMOC)
485 inductive loop detectors
Advanced Traveler Information Systems (ATIS):
19 dynamic message signs (DMS)
3 display travel times

6. Project Overview
Portland Regional Transportation Archive Listing (PORTAL)
Funded by NSF
Direct fiber-optic connection between ODOT and PSU
20-second loop detector data
Volume
Speed
Occupancy
Customized travel time area

7. Outline Project Overview Summary of Test Area Experimental Design
Data Collection
Data Comparison
Results
Next Steps

8. Summary of Test Area 15 directional freeway links I-5 (6) I-205 (3)
US-26 (2)
OR-217 (2)
Downtown Portland

9. Outline Project Overview Summary of Test Area Experimental Design
Data Collection
Data Comparison
Results
Next Steps

10. Experimental Design
Analysis of PORTAL estimates to determine required number of runs
Data collection plan
5-10 runs required for most links
4 routes designed
Transitional periods targeted
Groups with 5-7 minute headways
Standard probe vehicle instructions

11. Outline Project Overview Summary of Test Area Experimental Design
Data Collection
Data Comparison
Results
Next Steps

12. Data Collection Hardware Software
Palm handheld computers
Magellan GPS devices
Software
ITS-GPS
Free
Available at
Individual runs and groups of probe vehicles
Variety of traffic conditions

13. Data Collection 87 probe vehicle runs
904 minutes (~15 hours) of collection time
516 miles of data
12 drivers
7 days

14. Outline Project Overview Summary of Test Area Experimental Design
Data Collection
Data Comparison
Results
Next Steps

15. Data Comparison Probe data Individual runs downloaded
Runs plotted on freeway network map showing link endpoints
Pertinent data segments extracted
first point on Link 3
last point on Link 9
last point on Link 2

16. Data Comparison Detector data Assignment of influence areas
Midpoint method
ODOT modified midpoint method
Aggregation
Nearest 20-second interval
e.g. 9:15:34  9:15:20
Average of nearest interval and 1 minute before
Average of nearest interval and 3 minutes before

17. Outline Project Overview Summary of Test Area Experimental Design
Data Collection
Data Comparison
Results
Next Steps

18. Results
ATMS estimates reasonably accurate

19. Results ATMS estimates reasonably accurate Probe Vehicle
Projected Trajectory
Other Projections

20. } Results } Detector density and location critical ~ 2 minutes (4 mi.)
Probe
Projection
Influence Area Limit }
~ 11 minutes (8 miles)

21. Results
Incidents difficult to capture

22. Results No uniform difference between methods
Aggregation improves accuracy
(b) Average of previous 1 minute
(c) Average of 3 previous minutes
(a) Nearest 20 second estimate

23. Results Candidate locations for increased detection
Recurring congestion
Detector spacing > 1 mile
Hwy 217 NB at MP 3.2
US-26 EB at MP 70
US-26 WB at MP 69
US-26 WB at MP 70
I-5 NB at MP 298.5
I-5 SB at MP 306.5
I-84 EB at MP 2.0

24. Outline Project Overview Summary of Test Area Experimental Design
Data Collection
Data Comparison
Results
Next Steps

25. Next Steps More data Different algorithms Incidents Transitions
Historical data
Other detectors (e.g. Coifman)

26. Acknowledgements Oregon Department of Transportation Castle Rock
Stacy Shetler
Galen McGill
Dennis Mitchell
Jack Marchant
Castle Rock
Consultants
Dean Deeter
Student drivers