1. Transportation leadership you can trust. presented to Talking Operations Webinar presented by Richard Margiotta Cambridge Systematics, Inc. June 28, 2006 Uses of Travel Time Reliability

2. 1 Why is Reliability Important? Reliability is an indication of how travel times vary from day-to-day … OR … How consistent is travel? How predictable is travel? Variability in travel times means that extra time must be planned for (the aforementioned Buffer). In other words, travelers have to leave earlier to account for the Buffer

3. 2 Why is Reliability Important? (cont.) The Buffer has costs associated with it Planned extra time at least as costly as regular travel time Some studies place the Buffer’s costs at 2-6 times higher than average travel time Some trips will still exceed the Buffer – late penalties Some trips will take much less than the Buffer – early arrival penalties Reliability (or the lack of it) just says that travel times are inconsistent/variable – it doesn’t tell you why!

4. 3 So Why Do Travel Times Vary? Seven Sources of Unreliability 1. Traffic incidents 2. Special events 3. Work zones 4. Weather 5. Day-to-day demand (volume) fluctuations 6. Traffic control devices (railroad crossing, poor signal timing) 7. Inadequate base capacity

5. 4 A Model of Congestion and Its Sources n = Source of Congestion Base Delay (“Recurring” or “Bottleneck”) Physical Capacity …interacts with… Demand Volume 4

6. 5 A Model of Congestion and Its Sources n = Source of Congestion Base Delay (“Recurring” or “Bottleneck”) Physical Capacity …interacts with… Demand Volume 4 Daily/Seasonal Variation Special Events Planned …determine… Emergencies 23

7. 6 A Model of Congestion and Its Sources n = Source of Congestion Base Delay (“Recurring” or “Bottleneck”) Physical Capacity …interacts with… Demand Volume Daily/Seasonal Variation Special Events Planned …determine… Emergencies 231 …lowers capacity and changes demand… Traffic Control Devices Roadway Events Weather Incidents Work Zones 5 6 7 …can cause…

8. 7 A Model of Congestion and Its Sources n = Source of Congestion Base Delay (“Recurring” or “Bottleneck”) Physical Capacity …interacts with… Demand Volume 4 Event-Related Delay Total Congestion Daily/Seasonal Variation Special Events Planned …determine… Emergencies 231 …lowers capacity and changes demand… Traffic Control Devices Roadway Events Weather Incidents Work Zones 5 6 7 …can cause…

9. 8 Effects of Incidents and Weather on Reliability

10. 9 Changes in a High Growth Corridor

11. 10 Use of Reliability: Congestion by Source Where should we be concentrating our resources and effort? National programs State programs Corridor-specific programs

12. 11 Current Estimates of Delay by Source: National

13. 12 Some Empirical Results (Freeway Corridors) Los Angeles Seattle San Francisco Albany Recurring 69% 71% 80% 72% Incident 31% 16% 13% 28% Work Zone 0% Not inc. Weather 0% 9% 2% Not inc. Special Ev. 0% Not inc. 5% Not inc. High Vol. Not inc. 4% Not inc.

14. 13 The Effect of Treating Unreliability: I-75 Central Atlanta, 2002, SB, 4-7 PM

15. 14 Operator’s View of Reliability: What’s Happening Now Compared to “Normal”

16. 15 Use of Reliability: Performance Measurement Part of a comprehensive program to monitor congestion trends and operational effectiveness Can be applied at management, planning, and operations levels

17. 16 Overall Reliability Travel conditions are unreliable (Variable over time) USED BY MEASURES WHAT THEY TELL YOU Upper Management Public Relations Planners Delay by Source e.g., vehicle-hours What ’ s causing unreliable travel (e.g., incidents, weather, work zones) Mid-Management Operators Planners Work Zones Weather Special Events Incidents Traffic Control Demand- Variability Base Capacity Activities, Procedures, and Policies What aspects of operations, management, and construction need to be improved Operators Field Managers … for incidents … e.g., buffer index INCIDENT TIMELINE Incident Occurs Incident Recorded into CAD (Detection) Incident Verified Personnel Dispatched and Actions Initiated Responders Arrive to Scene Incident Cleared and Actions Canceled Return to Normal Conditions 6:35 A.M. 6:42 A.M. 6:47 A.M. 6:49 A.M. 6:50-7:00 A.M. 7:15 A.M. 8:26 A.M. 1 2 3 4 5 6 Detection Time Verification Time Dispatch Time Response Time Clearance Time Time to Normal Conditions Level 1Level 2Level 3

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20. 19 Other applications/studies Goods movement study, Southern CA Assoc. of Governments “Travel time reliability at international border crossings,” FHWA “Travel times in freight-significant corridors,” FHWA National Transportation Operations Coalition SHRP II: “Providing a Highway with Reliability Travel Times”

21. 20 SCAG Goods Movement Study Speed Trucking Industry Value-of-Time: $25 to $200 per hour depending on cargo Analysis Assumption: $73 per hour (2005 $) Reliability Unexpected delays can increase Value-of-Time by 50 to 250 percent

22. 21 Relationship Between Reliability and Congestion Level

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24. 23 SHRP II Research Program Reliability one of four SHRP II Program Areas (along with “Renewal”, “Safety”, and “Adding New Capacity” Four Reliability topic areas Building a Foundation and Institutional Setting for Operations (5 projects) Tools and Techniques for Advancing Operations (4 projects) Integrating Operations into Agency Decision-Making (2 projects) Developing Improved Operational Strategies (5 projects)

25. 24 Resources FHWA Traffic Congestion and Reliability Report http://www.ops.fhwa.dot.gov/congestion_report/index.htm NTOC http://www.ntoctalks.com/action_teams/perf_measure.php NCHRP 3-68, Freeway Performance Measures (Fall 2006) WSDOT Activities http://www.wsdot.wa.gov/Accountability/