1. Evaluation the Data Accuracy of Loop Detectors in Adaptive Signal Control Systems
Meead Saberi K., Portland State University
Vahab Esmaeli, Ferdowsi University of Mashhad, Iran
Ali Hatami, Ferdowsi University of Mashhad, Iran

2. Objective How accurate are the loop detectors data (count data)?
Is there any relationship between traffic volume and error rate of count data?
What are the reasons for error?

3. Study Area IRAN 6 main urban intersections in Mashhad city
Khayyam – Malek Abad intersection
Modarres – Emam Khomeini intersection
Sanabad – Kolahdooz intersection
Rah Ahan intersection
Sajjad – Bozorgmehr intersection
Daraie Intersection
6 main urban intersections in Mashhad city
(white square points on the map)

4. Data Quality Accuracy Completeness Validity Timeliness Coverage
“Data quality is the fitness of data for all purposes that require it. Measuring data quality requires an understanding of all intended purposes for that data”
Turner, S., Defining and Measuring Traffic Data Quality
Texas Transportation Institute Cambridge Systematics Inc, 2002.
Accuracy
Completeness
Validity
Timeliness
Coverage
Accessibility

5. Methodology
Study approaches were categorized into approaches with two, three and four lanes in which one loop detector installed in each lane.
Archived traffic volume data, aggregated at 15 minutes intervals, of each approach during the study period were used.
Recorded videos during the same periods were processed manually by two persons to count the actual number of passenger cars, heavy vehicles, motorcycles, and bicycles pass the detectors.

6. Detected traffic volume
Error Ratio
Actual traffic volume
Detected traffic volume
Error ratio is positive which means the actual traffic volume is smaller than the volume which loops are detected .
Error ratio is negative which means the actual traffic volume is greater than the detected number by loop detectors.

7. Reasons of Error

8. Reasons of Error

9. Reasons of Error

10. Reasons of Error

11. Reasons of Error

12. Volume vs. Error (4 lanes)

13. Volume vs. Error (4 lanes)

14. Volume vs. Error (4 lanes)

15. Volume vs. Error (4 lanes)

16. Volume vs. Error (3 lanes)

17. Volume vs. Error (3 lanes)

18. Volume vs. Error (2 lanes)

19. Hypothetical Relationship
Volume vs. Error

20. Next Step
Expanding the sample size to prove the relationship between volume and error

21. Acknowledgement Traffic Control Center of Mashhad
Ferdowsi University of Mashhad, Iran
STEP, Portland State University

22. Questions?
Thanks