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June 2006 ITE District 6 Annual MeetingJune 26 2006 1
Evaluation of Single-Loop Detector Vehicle-Classification Algorithms using an Archived Data User Service System
Benjamin Auffray,Kristin A. Tufte, Zachary Horowitz, Spicer Matthews,Robert L. Bertini Portland State University
June 2006, ITE District 6 Annual Meeting
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Presentation outline
• Introduction• Project Background• Data Collection• Results• Conclusions• Next Steps• Acknowledgements
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Why collect freight data?
• Economic importance
• Lack of knowledge of freight transportation system operation
• Safety and security
• Positive affects on overall transportation system
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Project background
Basic idea: Record freeway traffic in order to compare truck counting methods
3 methods:
1) Manual
2) Autoscope “speed” and “count” detectors
3) Nihan-Wang algorithm (UW)
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Data sources• PORTAL
• Portland area traffic data archive• Collects volume & occupancy data at 20 second intervals
• ODOT surveillance CCTV network• About 80 cameras on local highways• Recorded to DVD• Used for both manual counts and Autoscope
• Autoscope• Recorded video data processed using RackVision and accompanying software
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Site selection
4 locations in Portland, OR
I-5 SB at Marine Dr.I-84 WB at Sandy Blvd/37th
I-5 NB at Lower Boones Fy.OR-217 at SW Hall Blvd
10 days over 4 weeks
Traffic recorded primarilyFrom noon to 5 pm
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Data organization and processing• Manual count data sorted by:
• Lane• Vehicle type (short / long / combined)
• Cumulative and oblique plots• Histogram of Autoscope speed detector data used for length determination in some cases
-80
-60
-40
-20
0
20
40
11:40 11:55 12:10 12:25 12:40
Time
N(L
ow
er
Bo
on
es
Fe
rry,
t)
Manual count
Autoscope speed detector
PORTAL-Wang
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Graphical plots
Cumulative count of all vehicles
Oblique graph of allvehicles plotted usinga scaling factor
Oblique graph of shortvehicles using a scaling factor
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Comparison data
Total Count
0
200
400
600
800
1,000
1,200
1,400
1,600
1,800
2,000
0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000
Predicted Values
Man
ual
Co
un
t
Autoscope
Autoscope Speed
Portal-Wang
Series4
Comparison of total count mechanisms to ground truth
Truck Count Percent Difference
-50%
-25%
0%
25%
50%
75%
100%
125%
150%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
Hour
Per
cen
t D
iffe
ren
ce
Autoscope SpeedPortal-Wang
=4.4%=6.7%=44.1%, =41.6%
Truck count percent difference
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Comparison dataSpeed Relation to All Count Error
-10%
-8%
-6%
-4%
-2%
0%
2%
4%
6%
8%
10%
40 45 50 55 60 65
Measured Speed
Per
cen
t D
iffe
ren
ce
Autoscope
Portal Wang
Note: two outliers removed.
Measured average speed relation to all count error
Comparison by site
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Conclusions• Nihan-Wang estimations
• Unusually large error for some speeds and counts• Detector issues such as loop sensitivities• Incorrect or missing data
• Autoscope• Difficulties in calibration and data processing• Returned some favorable results compared to ground truth• ODOT surveillance camera system not ideal for Autoscope
• Manual counts still produce best data
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Next steps• Additional data collection
• Detector fidelity is key• Different sites may produce better data• Vehicle classification by type
• Further statistical testing• PORTAL data calibration will improve Nihan-Wang algorithm implementation results• Travel time estimation for freight vehicles• Permanent, automated freight vehicle counting• Ramp meter speed trap installations
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Acknowledgements• ODOT TMOC Staff
• Dr. Robert Bertini • PORTAL Team:
• Dr. Kristin Tufte• Spicer Matthews
• Zachary Horowitz
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References[1] Y. Wang and N. Nihan. Dynamic estimation of freeway large truck volume based on single-loop measurements. CD-Rom for the 80th Annual Meeting of TRB, paper 01-2853, TRB, National Research Council, Washington D.C., 2001. [2] Kwon, Jaimyoung. Joint Estimation of the Traffic Speed and Mean Vehicle Length From Single-Loop Detector Data. CD-Rom for the 82nd Annual Meeting of TRB, National Research Council, Washington, D.C. 2003. [3] Kwon, Jaimyoung; Varaiya, P. P.; Skabardonis, Alexander. ESTIMATION OF TRUCK TRAFFIC VOLUME FROM SINGLE LOOP DETECTOR USING LANE-TO-LANE SPEED CORRELATION. CD-Rom for the 82nd Annual Meeting of TRB, National Research Council, Washington, D.C. 2003. [4] Nihan, NL; Wang, Y; Zhang, XP. EVALUATION OF DUAL-LOOP DATA ACCURACY USING VIDEO GROUND TRUTH DATA. TransNow, Transportation Northwest, Washington Univ, Civil Engineering Dept, 2002. [5] Y. Wang and N. Nihan. Can Single-Loop Detectors Do the Work of Dual-Loop Detectors? ASCE Journal of Transportation Engineering, 129(2), 169-176, 2003 [6] National ITS ADUS Addendum [7] S. Turner. Guidelines for Developing ITS Data Archiving Systems. Report 2127-3. FHWA, U.S. Department of Transportation, Texas Department of Transportation and Texas Transportation Institute, 2001. [8] Y. Wang and N. Nihan. A Robust Method of Filtering Single-Loop Data for Improved Speed Estimation. CD-Rom for the 81st Annual Meeting of TRB, paper 02-3843, TRB, National Research Council, Washington, D.C. 2002. [9] P. Athol. Interdependence of Certain Operation Characteristics within a Moving Traffic Stream. Highway Research Record 72, 58-87.
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Questions and Comments