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Validation of Speeds and Volumes in a Large Regional Model

Validation of Speeds and Volumes in a Large Regional Model. Southeast Regional Planning Model – 6 Florida Department of Transportation District IV. SERPM 6 Corradino AECOM Consult. Consultant Team. With thanks to … FDOT Districts 4, 6 & Turnpike

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Validation of Speeds and Volumes in a Large Regional Model

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  1. Validation of Speeds and Volumes in a Large Regional Model Southeast Regional Planning Model – 6 Florida Department of Transportation District IV CORRADINO May 9, 2007

  2. SERPM 6 Corradino AECOM Consult Consultant Team • With thanks to … • FDOT Districts 4, 6 & Turnpike • MPO staffs of Palm Beach, Broward 7 & Miami-Dade Counties • SFRTA CORRADINO May 9, 2007

  3. SERPM 6 • Palm Beach, Broward and Miami-Dade Counties • 4,134 TAZs (ZONESA) • 3 Time periods (AM 6:30-9:30, PM 3:30 – 6:30, Off-peak) • 10 Transit modes • 22 – 28 hours run time on 3.4 GHZ computer CORRADINO May 9, 2007

  4. SERPM 6 - Transit Nets CORRADINO May 9, 2007

  5. Setup controls and file names External – EE by period Trip Gen – LSGEN by auto ownership and TOD Highway – Including speed and capacity calculators Distribution – Including equilibration of peak period highway speeds Transit Nets – PT  Trnbuild and connectors, paths, skims and fares Mode Choice Transit Assignment by access path and TOD Highway Trip Tables – Combines trip tables for assignment Highway Assignment – by TOD (use most computer time) Highway Evaluation – HEVAL and RMSE by TOD and county SERPM 6 – Model Flow CORRADINO May 9, 2007

  6. THE ISSUE • FTA/FHWA emphasis on correct speeds and travel times in models, especially for New Starts • So, we must: • Match traffic counts and transit ridership in the base year. • Match observed highway travel times • Match observed transit travel times CORRADINO May 9, 2007

  7. Old Practice • Assign uncongested speeds and capacities to links from a lookup table indexed by area type (AT), facility type (FT) and number of lanes. • Default lookup table developed by examining practice throughout the state. • Adjust the lookup table to obtain a better match of final assigned 24-hour volumes. • Most adjustments made to speeds. • Care taken to ensure “logical” relationships, e.g., freeways faster than arterials, rural faster than residential. • Transit speeds derived from highway using “INET” functions based on mode, AT and FT. CORRADINO May 9, 2007

  8. Well, What’s Wrong With That? • Lookup table probably better than adjusting individual links to get better loads (not dead yet – what speed does a new link get?). • While lookup tables are systematic, their contents can become arbitrary and skewed. • Seldom checked to verify they have any relationship to reality. CORRADINO May 9, 2007

  9. New Approach • Base Capacities on Florida Quality/Level of Service Manual, derived from HCM. • Capacities and speeds determined from roadway characteristics, not a subjective determination of AT, FT. • Speeds begin with POSTED SPEED, modified by studies of driver behavior. • If signal controlled, add estimated delays at intersections, but not microsimulation (somewhat of a slippery slope). • Some concessions were made to better match counts. CORRADINO May 9, 2007

  10. Initial Speed Estimation • Estimates uninterrupted flow initial speed from an equation. • Begin with NCHRP 387 • Modify to make more consistent (remove discontinuity at 50 mph). • Adds delays from traffic control devices • Later, speeds are changed in the user equilibrium assignment and equilibration of travel times. CORRADINO May 9, 2007

  11. Speed Relationships FWY=12.56+0.641*Postspd+0.00340*Postspd^2 Surface=9.10+0.657*Postspd+0.00348*Postspd^2 CORRADINO May 9, 2007

  12. CAPACITIES • New with SERPM-6. • Replaces the lookup tables. • Allows an OVERIDE coded on the link. • Based on the FDOT Quality/Level of Service Manual. • Script calculates LOS “C” and “E”. • Calculated as PCE’s. CORRADINO May 9, 2007

  13. Capacity Calculation Variables/Attributes CORRADINO May 9, 2007

  14. Time of Day • FSUTMS uses auto speeds from 24-hour assignment as for HBW mode choice • HBO & NHB use free-flow speeds • SERPM6 uses time of day • Peak period trips use AM congested speeds • Off-peak period trips use free-flow speeds • Standard FSUTMS design expected for most models CORRADINO May 9, 2007

  15. Equilibration • Peak speeds and time modified from user equilibrium assignment. • Run twice to conserve model running time. • Speeds found to be stable. • Produces distribution and mode choice travel times for highway and transit that are close to the times after the final assignment. • Times are stable for UB calculations. CORRADINO May 9, 2007

  16. SERPM 6 – Mode Choice Applied for Peak and Off-peak CORRADINO May 9, 2007

  17. SERPM 6 – Highway Assignment • By Time-of-Day • AM Peak • Off-Peak • PM Peak • Composite 24 Hours (add preceding) CORRADINO May 9, 2007

  18. Volume-Delay CurvesSoutheast Regional Planning Model VI CORRADINO May 9, 2007

  19. SERPM 6 – Highway Evaluation • SUMMARIES BY: • SERPM 6 Region by Time-of-Day • Each County for 24 hours • Trucks alone – each County for 24 hours CORRADINO May 9, 2007

  20. SERPM 6 - Validation • Standard FSUTMS • Plus Speed Validation • Speed compromises made in favor of Volume/Count • Good Volume/Count ratios • Very good RMSE • Good transit assignment results CORRADINO May 9, 2007

  21. Highway Sections of Observed Speed Study(from several sources) CORRADINO May 9, 2007

  22. 2000 Highway Speeds CORRADINO May 9, 2007

  23. SERPM 6 – Speed Validation CORRADINO May 9, 2007

  24. AM PeriodSpeedValidation CORRADINO May 9, 2007

  25. PM PeriodSpeedValidation CORRADINO May 9, 2007

  26. Off-PeakSpeedValidation CORRADINO May 9, 2007

  27. SERPM 6 – Systemwide Comparison CORRADINO May 9, 2007

  28. SERPM 6 – RMSE Validation CORRADINO May 9, 2007

  29. Highway Screenline Accuracy CORRADINO May 9, 2007

  30. ScreenlineLocations CORRADINO May 9, 2007

  31. Volume/Count Ratios of Screenlines CORRADINO May 9, 2007

  32. Conclusions • Assigning speeds to network links based on posted speeds and traffic control produces good results in terms of speeds and travel times. • The Florida Quality/Level of Service Manual is useful for estimating model capacities. • Speed and capacity calculators appear to work at least as well as lookup tables and are less arbitrary. • It is possible to validate speeds and volumes in a time-of-day model. CORRADINO May 9, 2007

  33. Recommendations for Future Study • Need consistent travel time data. • Need more travel time data. • Consider estimating delays at intersections dynamically using software intersection or junction modeling. • Better way of estimating the impacts of freeway merge/diverge/weaves on model travel times. CORRADINO May 9, 2007

  34. Questions ? Please use the Microphone. CORRADINO May 9, 2007

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