1. L08: INCORPORATING RELIABILITY INTO THE HCM FREEWAY AND MULTILANE SUBCOMMITTEE JANUARY 22, 2012 Kittelson & Associates, Inc. Cambridge Systematics Dowling Associates, Inc. Texas Transportation Institute ITRE – NC State Lily Elefteriadou 1

2. 2 AGENDA Quick presentation and demo of freeway scenario generator Feedback needed from the subcommittee Discussion and next steps

3. FREEWAY SCENARIO GENERATOR WHAT IS A SCENARIO ? A scenario is a unique combination of facility demand and capacity patterns resulting in one estimate of facility travel time or other MOE. The smallest time unit over which a MOE is generated is an analysis period. Typically however we associate the naming of a scenario with a study period. Changes in demand and capacity may be due to regular (calendar based) or non-regular (non- calendar based) events. Type of non-recurring events include weather, incidents, work zones and special events 3

4. FREEWAY SCENARIO GENERATION (2) VARIABILITY BETWEEN SCENARIOS ARISE FROM: Systematic Demand variability between weekdays and weekends and months of year. Hourly variability reflecting peaking patterns in demand—both more or less calendar based Demand variability due to special events, scheduled work zones and possibly weather--- some random, some calendar-based Capacity variability due to weather, incidents, special events, work zones and traffic control, some random, some calendar based Approach is transparent…. –All scenarios attributes fully defined PRIOR to HCM analyses and –Probability of each scenario also COMPUTED PRIOR to HCM analyses –HCM computations attach a predicted travel time to the probability 4

5. FREEWAY SCENARIO GENERATION (3) THE GENERATION PROCESS INVOLVES 8 STEPS. ALL ANALYSES APPLY TO A STUDY PERIOD (SP) 1. Definition of:  Analysis period- AP ( 15 min for freeway facilities)  Study period-SP(typically multiple hours in peak– user input)  Reliability reporting period-RRP (typically one year – user input) 5

6. FREEWAY SCENARIO GENERATION (4) 2. Definition of demand variability –Day of week, month of year, hours of day 6

7. FREEWAY SCENARIO GENERATION (5) 3. Probability of weather, incidents, work zones, special events 7 WZ No. WZ Start DateWZ End Date Number of Lanes Closed Demand Multiplier Capacity Multiplier MonthDayMonthDay 1111510.90.70 24342000.850.95

8. FREEWAY SCENARIO GENERATION (6) 8

9. FREEWAY SCENARIO GENERATION (7) 9

10. FREEWAY SCENARIO GENERATION (8) 10

11. FREEWAY SCENARIO GENERATION (9) 11 Quality of sample vs. population distribution

12. Next Steps Finalize generation of detailed incident characteristics –Location-Duration-Start Time Run and evaluate test data (I-40 and Portland) Develop regional default weather / incident exposure models Interface between Scen-Gen and FREEVAL Generate performance measures Run validation data sets 12

13. 13 INPUT NEEDED In reporting reliability statistics must the team include ? Scheduled / major work zones occurring on the facility Scheduled special events that occur on or impact the facility Upside & downside of inclusion or exclusion (remove the dates from the RRP) Is subcommittee agreeable with proposed approach of modeling incidents including Incident probability calculations? Keeping incident location, duration and start times fixed in FREEVAL? Upside and downside The team proposes a procedure for freeway that is fully deterministic…… that is if the user enters one set of data, they will get exactly one distribution of travel times (or other MOE) and one set of reliability measures… is that OK? Too much burden on the analyst to gather the required facility specific input data ? Or should the team strives to use defaults as much as possible

14. 14 Is subcommittee agreeable with the concept of sampling from the population of scenarios? Should the sample size be left to the discretion of the user? Related… Any sense on what may represent a reasonable number of scenarios to run with the core HCM engine to the group? Is there a willingness to consider, say 100 or 1,000? Upsides and downsides to both approaches. Need feedback on the final outcome of the freeway scenario generator itself (synthetic TTI distribution), and whether it could be adopted as THE planning-level method for freeway reliability analysis (with modifications) The team proposed that variability in travel times and other MOE’s be reported at the analysis period levels? Any issues with that decision ? F&M SUBCOMMITEE INPUT NEEDED Any other comments or feedback from the subcommittee ?