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Traffic Counts and Travel Model Performance

Item 9. Traffic Counts and Travel Model Performance. A Presentation to the TPB Technical Committee April 1, 2005. Traffic Counts and Model Evaluation. The ‘Yardstick’ of Model Performance Regional/Jurisdictional VMT Screenline/Cutline Crossings Air Quality Requirements VMT Tracking

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Traffic Counts and Travel Model Performance

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  1. Item 9 Traffic Counts and Travel Model Performance A Presentation to the TPB Technical Committee April 1, 2005

  2. Traffic Counts and Model Evaluation • The ‘Yardstick’ of Model Performance • Regional/Jurisdictional VMT • Screenline/Cutline Crossings • Air Quality Requirements • VMT Tracking • Emission Budgets • Increasing Specificity Sought • AADT, AAWDT, Seasonal, Time of day, Classification, etc. Presentation to the TPB Technical Committee 4/1/05

  3. Model Performance is Relative • Performance is an Estimated-to-Observed Ratio • Regional, Subregional, Jurisdiction, Screenline, Link, … • Performance Depends on Accuracy of Both Estimated and Observed Figures • A Balanced Understanding of Both Estimated and Observed Figures is Critical to Validation Presentation to the TPB Technical Committee 4/1/05

  4. Traffic Counts in the Region • Highway Performance Monitoring System (HPMS) is Primary Source of Count Data • DDOT, MDSHA, VDOT, Local Jurisdictions • AADT (MD) / AAWDT (DC and VA) • Coding Counts in the Highway Network • Historically a Manual Process Using Count Books/Maps • More Recently Electronic Transfer Using Georeferenced Count Data Bases and COG’s Transportation Data Clearinghouse • Data Used ‘as is’; Maximum Link Coverage Sought Presentation to the TPB Technical Committee 4/1/05

  5. HPMS Overview • Samples Designed for Statewide Traffic Estimates • Permanent Counting Stations, Continuous Operation • Program Count Locations; Short Count Duration, 3-year Collection Cycle • Adjustments Applied to Counts • Current-year Program Counts Annualized • Non-Current Year Program Counts Adjusted to Current Year • Partially Operational Permanent Counts Annualized • “Manual Adjustments” made to compensate for Equipment Failure, Construction, Safety Issues, etc. • Adjustments based on Perm.Counts Statewide Presentation to the TPB Technical Committee 4/1/05

  6. Observations on the HPMS • HPMS is not a count of traffic, per se-- HPMS is an annualized traffic volume estimate based on a statewide sample of a limited number of locations. • A Case Can be Made: Model Performance expressed as an ‘Estimated-to-Observed’ Ratio Should be Considered as an ‘Estimated-to-Estimated’ Ratio • When HPMS data is used for a specific metropolitan area, data noise is a potential issue. Presentation to the TPB Technical Committee 4/1/05

  7. Issues for Transportation Modeling • Highway Network is an Approximation of the Physical Roadway System • Resolving AADT Figures to AAWDT is Approximate • Directionality of Counts is Suppressed With HPMS Data • Ground Count Highway Network Coding Practices Can Also Introduce Noise/Bias Into the Performance Statistics Presentation to the TPB Technical Committee 4/1/05

  8. Daily VMT Over Timefor the Washington Region By State Presentation to the TPB Technical Committee 4/1/05

  9. Time Series VMT Changefor the Washington Region By State Presentation to the TPB Technical Committee 4/1/05

  10. Yr 2000 Validation Freeways RMSE Summary Presentation to the TPB Technical Committee 4/1/05

  11. Updated Traffic Volume Estimates for V2.1.D Model Performance Tests • Review Traffic Volume Data/ Estimates for all jurisdictions in the metropolitan Washington region (MSA). • Link AAWDT Traffic Volume Estimate only to the network link where the Program or Permanent Counting Station was located (i.e. no carrying forward or averaging volume estimates for adjacent links). • Identify all Program and Permanent Counting station locations where actual traffic count data was collected in Year 2000. • Identify all Permanent Counting Stations that were operational in Year 2000. Presentation to the TPB Technical Committee 4/1/05

  12. All Program and Permanent Counting Locationswith Actual or Factored Daily Traffic Volume Estimates for Year 2000 Presentation to the TPB Technical Committee 4/1/05

  13. All Program and Permanent Counting Locationswith Actual Traffic Count Data Collected in Year 2000 Presentation to the TPB Technical Committee 4/1/05

  14. All Operational Permanent Counting Station Locations in Year 2000 Presentation to the TPB Technical Committee 4/1/05

  15. Performance Test Results Presentation to the TPB Technical Committee 4/1/05

  16. Validation E/O Scatterplots11,004 Observations Presentation to the TPB Technical Committee 4/1/05

  17. Permanent /Actual & Factored Program Counts 2,953 Observations Presentation to the TPB Technical Committee 4/1/05

  18. Permanent /Actual Program Counts 1,194 Observations Presentation to the TPB Technical Committee 4/1/05

  19. Permanent Count Stations68 Observations Presentation to the TPB Technical Committee 4/1/05

  20. Conclusions • Model Performance Improves with Higher Quality Counts • Metropolitan areas using statewide counting program data should expect count accuracy limitations-- especially multi-state areas. Consider metropolitan samples? • Expect scatterplot outliers, seek explanations • Performance problems does not equate to model problems. Presentation to the TPB Technical Committee 4/1/05

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