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  1. The Secrets to HCM Consistency Using Simulation Models • Given by: • Ronald T. Milam, AICP • Contributing Analysts: • David Stanek, PE • Chris Breiland • Mike Iswalt Transportation Research Board Planning Applications Conference, May 2007

  2. Typical Simulation Examples

  3. When to Use Simulation

  4. When to Use Simulation

  5. When vs. How? • The HCM methodologies may not be appropriate in environments with multiple travel modes or multiple hours of congestion. • “… the HCM methods are generally not appropriate…for the evaluation of queues that are building over both time and space.” – Page 9-1, HCM 2000 • “ Certain freeway traffic conditions cannot easily be analyzed by the methodology. Multiple overlapping bottlenecks are an example. Therefore, other tools may be more appropriate…” - Page 22-1, HCM 2000

  6. Challenges/Issues • Multiple software packages • AIMSUN • CORSIM • Dynasim • Paramics • SimTraffic • TransModeler • VISSIM • others… • Which ones are HCM consistent? • How can a user or reviewer be sure?

  7. Simulation Performance Measures • Traffic simulation programs provide many performance measures • Total delay • Density • Travel time • Average speed • Travel distance • Number of stops • However, the definition of the performance measures may differ from the HCM definition. • Stopped delay • Throughput • Emissions • Fuel consumption • Queue length • Others

  8. HCM Performance Measures • HCM methods determine LOS for facility types based on different performance measures • Facility Type • Intersections • Urban Streets • Two-Lane Highways • Multi-lane Highways • Freeways • Performance Measure • Control Delay • Speed • Percent Time Spent Following • Density • Density

  9. Consistency Issues • Roadway System • Peak hour factor • Intersections • Defining the intersection approach • Freeways • Ramp influence areas

  10. Peak 15-Minute Volume Peak Hour Peak Hour Volume Peak Hour Factor • HCM defines the LOS for the peak 15 minutes of the peak hour

  11. Peak Hour Factor, continued… • Edit the periods file to create 15-minute interval demand periods. Paramics Example

  12. Peak Hour Factor, continued… Use the divisor parameter in the demands file to adjust peak hour volumes. Hourly data with PHF of 0.95 implies a divisor of 3.8. Paramics Example

  13. Maximum Queue Intersection Approach Delay • Include delay for all vehicles on approach • Model link delay may not include entire intersection approach Model Network

  14. Intersection Approach Delay, continued… • Upstream unsignalized intersection divides the southbound approach into two links. SimTraffic Example

  15. Intersection Approach Delay, continued… • Upstream unsignalized intersection divides the southbound approach into two links. Unsignalized Driveway Intersection Link 2 Signalized Intersection Link 1 SimTraffic Example

  16. Intersection Approach Delay, continued… • Output report for signalized intersection shows delay for Link 1 only. SimTraffic Example

  17. Intersection Approach Delay, continued… • Adding delay for Links 1 and 2 to get the entire southbound approach delay. SimTraffic Example • LOS ResultsLink 1Links 1 & 2 • SB Approach E / 59 F / 86 • Intersection D / 40 D / 44

  18. Ramp Influence Area • HCM defines the ramp merge analysis area as the two right shoulder lanes plus the auxiliary lane for 1,500 feet downstream of the ramp gore • Ramp influence area does not necessarily match model links

  19. Ramp Influence Area, continued… • Build model network to account for ramp influence area and volume collection locations. VISSIM Example

  20. 2,930 ft Ramp Influence Area 450 ft Ramp Influence Area, continued… • Ramp merge area with acceleration lane Link 191 Link 190 VISSIM Example On-Ramp

  21. 1,050 ft 450 ft Ramp Influence Area, continued… • Collect statistics for ramp influence area. VISSIM Example

  22. Ramp Influence Area, continued… • Collect statistics by lane for each link. VISSIM Example

  23. Across Links Across Links Across Lanes Across Lanes Ramp Influence Area, continued… • Calculate volume-weighted average density first across links, then across lanes VISSIM Example

  24. Ramp Influence Area Ramp Influence Area, continued… • Analysis Results • LocationDensity (vpmpl)LOS • Link 190 (all lanes) 42.4 E • Link 191 (all lanes) 37.2 D • Ramp Influence Area 42.1 E Link 191 Link 190 VISSIM Example

  25. Recommendations • FHWA - Modify NGSIM priorities to better reflect user needs • TRB - Update the HCM to provide specific guidelines for simulation software vendors and to reflect a wider range of performance measures • Software Vendors – Provide technical support and training on HOW to perform simulation modeling • Users – Invest time to understand HOW to perform simulation modeling

  26. The Secrets to HCM Consistency Using Simulation Models Questions?