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October 19 th , 2011

October 19 th , 2011. Validation of the Historical Vehicle Probe Project Speed by Using Bluetooth Speed as the Ground Truth. Elham Sharifi Stanley E. Young. 1. October 19 th , 2011. Agenda. Introduction Study Area Bluetooth Data Clean up Validation Methodology Results Conclusion. 2.

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October 19 th , 2011

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  1. October 19th, 2011

  2. Validation of the Historical Vehicle Probe Project Speed by Using Bluetooth Speed as the Ground Truth ElhamSharifiStanley E. Young 1 October 19th, 2011

  3. Agenda • Introduction • Study Area • Bluetooth Data Clean up • Validation Methodology • Results • Conclusion 2 October 19th, 2011

  4. Introduction • The I-95 Corridor Coalition sponsored the development of the Vehicle Probe Project (VPP). • UMD is responsible for validating the accuracy of the data provided by the VPP. • The Center for Advanced Transportation Technology (CATT) at the UMD developed a portable Bluetooth monitoring system to monitor vehicle travel times on highways. • This Bluetooth sensor is commercialized and now it’s available through Traffax Inc. 3 October 19th, 2011

  5. Introduction(cont.) • In addition to the speed and travel-time data the VPP also includes a quality metric called ‘Score’ • Score can have the following values: • “30” – high confidence, based on real-time data • “20” – medium confidence, based on historical data • “10” – low confidence, based on reference speed data 4 October 19th, 2011

  6. Introduction (cont.) • Daytime vs. Nighttime • 5AM to 10 PM : reverts to “20” • 10 PM to 5 AM: reverts to “10” 5 October 19th, 2011

  7. Introduction (cont.) • VPP also provides historical and reference speed data: • The historical speed is the average speed for the time of the day and day of the week. • The reference speed reflects the 85th percentile speed for the segment, which is indicative of free-flow speed. • It’s very important to see how historical speed and reference speed data performs relative to real-time data when compared to ground-truth speed. 6 October 19th, 2011

  8. Study Area • Bluetooth sensor deployments in Delaware started on November 3, 2010 and ended on November 17, 2010. • Travel time data was sampled from nine segments over 14 miles. 7 October 19th, 2011

  9. Bluetooth Data Clean up • Filtered Observations: • Observations with unreasonably low speed • Observations far from the average within a specified time interval • Also, when there are less than three observations in a five minute interval -The data was collected as part of the vehicle probe project funded by the I-95 Corridor Coalition. 8 October 19th, 2011

  10. Validation Methodology • The standard error of the mean (SEM) band is used for confidence limits on the ground truth data: • Based on the VPP validation methodology, performance is assessed in four speed ranges (0-30 mph, 30-45 mph, 45-60 mph, >60 mph). • SEB and AASE are used to evaluate VPP historical and reference speeds. 9 October 19th, 2011

  11. Validation Methodology (cont.) • SEB: speed error bias which is average error from SEM band • AASE: average absolute speed error from SEM band -The data was collected as part of the vehicle probe project funded by the I-95 Corridor Coalition. 10 October 19th, 2011

  12. Results Data Quality Measures During Daytime Hours (5am-10pm) SEB < 5 MPH AASE < 10 MPH -The data was collected as part of the vehicle probe project funded by the I-95 Corridor Coalition. 11 October 19th, 2011

  13. Results (cont.) Data Quality Measures During Nighttime Hours (10pm-5am) SEB < 5 MPH AASE < 10 MPH -The data was collected as part of the vehicle probe project funded by the I-95 Corridor Coalition. 12 October 19th, 2011

  14. Conclusion • During congested periods, the differences in performance between historical and real-time data are evident. • During periods of low data-density when the VPP reverts to historical data, severe congestion may be masked. • The real-time data significantly outperforms historical data, it is an indication that the VPP does provide real-time monitoring and is not simply a reflection of expected conditions. • Historical data outperforms reference data. 13 October 19th, 2011

  15. Acknowledgement • The data used in this paper was collected as part of the vehicle probe project funded by the I-95 Corridor Coalition. • The Bluetooth sensors used in this study were designed and manufactured by the Center for Advanced Transportation Technology at the University of Maryland, College Park. 14 October 19th, 2011

  16. Thank You October 19th, 2011 15

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