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Traffic Counts and Travel Model Performance

This presentation explores the importance of traffic counts and model evaluation in transportation planning. It covers the use of HPMS data, observations, HPMS overview, and issues for transportation modeling. The document also includes insights on daily VMT trends, model performance tests, validation results, and conclusions on improving model accuracy.

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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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