Reliability Workshop Presentation


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  • Wireless connectivity would enable roadway users to receive information to provide 360° situational awareness. In unsafe situations, IntelliDriveSM applications provide alerts and advisories, or take action to help roadway users avoid or mitigate crashes.
  • Reliability Workshop Presentation

    1. 1. Travel Time Reliability Brandon Nevers, P.E., PTOE March 4, 2010
    2. 2. Presentation Objectives <ul><li>Describe the current practice for how travel time reliability is: </li></ul><ul><ul><li>Defined </li></ul></ul><ul><ul><li>Measured </li></ul></ul><ul><ul><li>Improved </li></ul></ul><ul><ul><li>Predicted </li></ul></ul><ul><li>Highlight current applications of travel time reliability </li></ul><ul><li>Demonstrate how the benefits of travel time reliability strategies can be quantified </li></ul>
    3. 3. What is Reliability? <ul><li>By definition, reliability is an attribute of any system that consistently produces the same results </li></ul><ul><li>Travel time reliability is represented by statistical measures that describe the variability in congestion </li></ul><ul><li>The concept of travel time reliability represents a paradigm shift </li></ul>Future Past Increase Capacity Utilization Reduce Variability in Travel Time Increase Capacity Reduce Travel Time
    4. 4. What is Unreliability? <ul><li>Consider this example: </li></ul><ul><li>Sally lives 10 miles from work. Without any traffic it takes her 15 minutes door-to-door. On a normal day during rush hour it takes her about 25 minutes . On a bad day when there’s an incident or bad weather or something else, it takes her up to 40 minutes . </li></ul>WHEN SHOULD SALLY LEAVE TO ARRIVE ON TIME?
    5. 5. Day-to-Day Variations in Travel Time Source:
    6. 6. Factors Contributing to Reliability Operational Effect  Special Events   Reduced Lanes  Poor Signal Timing  Weather  Work Zones  Incidents  Recurring Congestion Increased Demand Reduced Lane Capacity
    7. 7. How is Reliability Different? Full Distribution Average Statistical Reporting Yes No Demand Effects Considered? All Recurring Type of Congestion Accounted For Multiple days Single Day Temporal Analysis Period Path/Network Point Spatial Element Analyzed Reliability-Focused Analysis Approach Traditional Analysis Approach
    8. 8. Why is Reliability Important? <ul><li>Our roadway networks are more frequently operating in a near or above capacity state </li></ul><ul><li>Uncertainties in travel time adversely impact us in multiple ways </li></ul><ul><li>We don’t have a way to measure the benefit of many of our strategies and investments </li></ul>Source:
    9. 9. Reliability Performance Measures <ul><li>General Observations </li></ul><ul><li>A variety of reliability performance measures have been defined and applied (no single metric) </li></ul><ul><li>The appropriateness of a reliability measure or set of measures is dependent on the application </li></ul><ul><li>Reliability measures do not address the productivity of our networks </li></ul><ul><li>Reliability measures generally relate travel time from a “bad day” to a normal or expected delay </li></ul>
    10. 10. Commonly Applied Reliability Measures The amount of buffer time required The difference between the 95 th percentile travel time and the average travel time Buffer Time Description Definition Measure The size of the buffer as a percentage of the average The 95 th percentile travel time minus the average travel time divided by the average travel time Buffer Index How much larger the potential total travel time is than the ideal or free-flow travel time The ratio of the Planning Time to the Ideal or Free Flow Travel Time Planning Time Index The total travel time required to arrive on-time 95% of the time 95 th percentile travel time Planning Time
    11. 11. Graphical Illustration of Reliability Measures Source:
    12. 12. Reliability Measures <ul><li>General Questions </li></ul><ul><li>What is the most effective way to measure reliability? </li></ul><ul><li>What data do I need and where/how do I get it? </li></ul><ul><li>What is a “desirable” or “acceptable” reliability measure? </li></ul><ul><li>How should reliability measures be weighed against traditional measures (i.e., Level of Service)? </li></ul>
    13. 13. Florida Department of Transportation Central Office <ul><li>Conducted pilot project to determine feasibility of adding reliability to existing reporting efforts </li></ul><ul><li>Planning-level application </li></ul><ul><li>Evaluated freeway system statewide </li></ul><ul><li>Developed hourly travel time profiles using ATR volume data </li></ul><ul><li>Next steps: incorporating real-time data and incident data </li></ul>
    14. 14. FDOT Pilot Study (Sample Results for I-95) 55% 59% 26 40 SR 708 US 98 126% 76% 17 39 US 98 SR 869 25% 37% 30 38 SR 869 I-595 56% 59% 25 39 I-595 FLA Turnpike 41% 50% 27 39 FLA Turnpike SR 924 97% 73% 21 42 SR 924 I-195 43% 47% 23 33 I-195 Dolphin Expy 137% 79% 17 41 Dolphin Expy SR 5 Buffer Index % Time the avg speed is < 10 mph less than uncongested speed 95 th % Speed (mph) Average Speed (mph) To From
    15. 15. ODOT Regional Arterial Enhancement Project <ul><li>Collaborative signal retiming effort that includes over 150 signalized intersections </li></ul><ul><li>One of the study corridors includes Beaverton Hillsdale Highway </li></ul><ul><li>Data collected using Bluetooth MAC readers </li></ul><ul><li>Allows for calculation of reliability measures in before/after comparison </li></ul>
    16. 16. BH Highway Corridor Travel Times Ideal 95th Free-flow Average 95 th Percentile Free Flow = 4.5 min Average = 6.2 min 95 th Percentile = 9.6 min Planning Index = 2.1 Buffer Index = 0.54
    17. 17. How can Reliability be Improved? TSM&O Travel Time Information Vehicle & Infrastructure Technology Incident & Event Management Performance Improvements
    18. 18. TSM&O <ul><li>“ Regional transportation systems management and operations (TSM&O) means an integrated program to optimize the performance of the existing infrastructure though implementation of multi-modal, cross-jurisdictional systems, services, and projects.” – FHWA </li></ul><ul><li>Four key elements: </li></ul><ul><ul><li>Awareness </li></ul></ul><ul><ul><li>Structure </li></ul></ul><ul><ul><li>Funding Priority </li></ul></ul><ul><ul><li>Partnerships </li></ul></ul>
    19. 19. Traveler Information Source: Better Traveler Information Improved Trip Decision Making Increased Capacity Utilization & Reliability
    20. 20. Vehicle and Infrastructure Technology = Source:
    21. 21. Incident and Event Management <ul><li>Pre-event </li></ul><ul><ul><li>construction phasing </li></ul></ul><ul><ul><li>evacuation planning </li></ul></ul><ul><li>Post-event </li></ul><ul><ul><li>coordinated response </li></ul></ul><ul><ul><li>service patrols </li></ul></ul><ul><li>Monitor and evaluate </li></ul><ul><ul><li>infrastructure to determine vulnerability </li></ul></ul><ul><ul><li>work zone management </li></ul></ul>
    22. 22. Performance Improvement Strategies Reduce and encourage alternative travel Travel reduction Multimodal travel Low-cost changes to the physical roadway section Lane treatments Access management Geometric design treatments Strategies that influence and respond to demand Congestion pricing Variable speed limits Traffic demand metering Signal timing/ITS
    23. 23. Non-Lane Widening Strategies to Improve Capacity Interchange Modifications VMS/DMS Alt LT Treatments Frontage Road In-Vehicle Info Right/Left Turn Channelization Weaving Section Pre-Trip Information Access Points HOT Lanes Truck Restrictions Raised Medians Pricing by Distance Truck Only Lanes Queue Management Congestion Pricing Variable Lanes Adaptive Signals Ramp Closures Reversible Lanes Signal Coordination Ramp Metering Narrow Lanes Signal Retiming HOV Lanes Both Arterial Freeway
    24. 24. Variable Speed Limits <ul><li>Brilon, Geistefeldt, et al. examined the stochastic capacity of a six-lane motorway in Germany </li></ul><ul><li>One direction was instrumented with VSLs, the other was not </li></ul><ul><li>An evaluation of freeway capacity showed the following effects of VSLs: </li></ul><ul><ul><li>Mean capacity increased by 3% </li></ul></ul><ul><ul><li>Standard deviation decreased by 20% </li></ul></ul><ul><li>Using a Whole-Year-Analysis which accounts for the operational effects of incidents and weather, annual delay savings were estimated to be 40% </li></ul>
    25. 25. Brilon and Geistefeldt. Implementing the Cost of Reliability for Highway Capacity Analysis, 56 th TRB Annual Meeting, Washington DC
    26. 26. Dynamic Traffic Assignment (DTA) Models <ul><li>DTA is an emerging modeling approach that estimates travel patterns and models driver behavior in “real time” </li></ul><ul><li>It builds a bridge between Travel Demand Models and Detailed Simulation Models </li></ul>
    27. 27. Truck Restricted Lane Analysis using DTA <ul><li>Modeled for a subarea in Ft. Worth Texas </li></ul><ul><li>Implemented along the southbound direction of a 5.2 mile segment of a 4-lane freeway facility </li></ul><ul><li>Truck restrictions placed on two left-most lanes </li></ul><ul><li>% Trucks = 20% </li></ul>Source:
    28. 28. Truck Restricted Lane Modeling Results General Purpose Lanes Truck Restricted Lanes 0.67 0.2 35 6.9 3840 48 Avg Strategy 0.4 55 11.6 4155 68 95 th % 0.20 0.50 Buffer Index 0.4 29 8.2 3105 63 95 th % 0.2 24 6.9 2920 46 Avg 0.8 0.4 Queue Length (mi) 51 36 Density (pc/mi/ln) 13.4 8.9 Travel Time (min) 6836 6502 VMT (veh*mi/15 min) 44 35 Speed (mph) 95 th % Avg MOE Baseline
    29. 29. Truck Restricted Lane Analysis Results
    30. 30. Quantifying the Economic Benefit of Reliability <ul><li>Certainty-Equivalent Approach </li></ul><ul><li>Converts the uncertainty associated with non-recurring and rare events to a certainty-equivalent measure </li></ul><ul><li>Answers the question: </li></ul><ul><ul><li>“How much longer is the travel time I would accept in return for no uncertainty about the travel time?” </li></ul></ul><ul><li>Determined using speed distribution curves developed from detector data </li></ul>Source: ECONorthwest
    31. 31. Certainty-Equivalent Approach Process
    32. 32. Benefit-Cost Analysis of Ramp Metering on SR 520 Floating Bridge for AM Peak (Seattle, WA) <ul><li>Certainty Equivalent </li></ul>Source: ECONorthwest 6.6: 1 Benefit-Cost Ratio $78,000 Total Cost (5 yrs) $112/mi Value of Reliability for Improvement 0.15 min/mi .20 min/mi Certainty Equivalent 0.30 0.37 Buffer Index 2.15 2.54 Planning Time Index After Before Measure
    33. 33. A Day in the Life, 2030 — Pre-travel <ul><li>Land Use </li></ul><ul><li>Need to Commute? </li></ul><ul><ul><li>Telecommute </li></ul></ul><ul><ul><li>Virtual reality </li></ul></ul><ul><ul><li>Robotics </li></ul></ul><ul><li>Traffic/Weather Forecast </li></ul><ul><li>Modal Contour Map </li></ul><ul><ul><li>Walk </li></ul></ul><ul><ul><li>Bike </li></ul></ul><ul><ul><li>Transit </li></ul></ul><ul><ul><li>Rideshare </li></ul></ul><ul><ul><li>Auto </li></ul></ul><ul><ul><li>Auto + x </li></ul></ul><ul><li>Pre-trip Guidance </li></ul><ul><ul><li>Load matching </li></ul></ul><ul><ul><li>Route/Mode Optimization </li></ul></ul><ul><ul><li>Traffic forecast by hour </li></ul></ul><ul><ul><li>Vehicle/driver inspection </li></ul></ul><ul><ul><li>Land use info </li></ul></ul>People Freight
    34. 34. A Day in the Life, 2030 — Traveling <ul><li>Vehicle Technologies </li></ul><ul><ul><li>Lean vehicles </li></ul></ul><ul><ul><li>Self-guiding vehicles </li></ul></ul><ul><ul><li>Incident avoidance </li></ul></ul><ul><li>Integrated Operations </li></ul><ul><ul><li>Reservation system </li></ul></ul><ul><ul><li>IntelliDrive </li></ul></ul><ul><ul><li>Adaptive signal control </li></ul></ul><ul><ul><li>Incident management </li></ul></ul><ul><li>Physical System </li></ul><ul><ul><li>Information </li></ul></ul><ul><ul><li>Holding areas </li></ul></ul><ul><ul><li>Reversible lanes </li></ul></ul><ul><ul><li>Work zone management </li></ul></ul><ul><li>Reservations </li></ul><ul><li>Modal transfer </li></ul><ul><li>Real-time adjustment to both freight and deliveries </li></ul><ul><li>Guidance </li></ul><ul><ul><li>Load matching </li></ul></ul><ul><ul><li>Parking </li></ul></ul><ul><ul><li>Routing </li></ul></ul><ul><ul><li>Mode jumping </li></ul></ul>People Freight
    35. 35. Key Resources <ul><li>FHWA </li></ul><ul><ul><li> </li></ul></ul><ul><ul><li>Urban Congestion Report </li></ul></ul><ul><ul><li>“ Selecting Travel Time Reliability Measures”, 2003 </li></ul></ul><ul><ul><li>“ Traffic Congestion and Reliability”, 2004 </li></ul></ul><ul><li>NCHRP </li></ul><ul><ul><li>NCHRP Research Reports Digest 312: Guide to Effective Freeway Performance Measurement </li></ul></ul><ul><ul><li>NCHRP Report 618: Cost Effective Performance Measures for Travel Time Delay, Variability, and Reliability </li></ul></ul>
    36. 36. Advancing the Reliability Practice: Strategic Highway Research Program 2 (SHRP2) <ul><li>6-year $150M research program authorized by Congress in 2006 </li></ul><ul><li>4 program areas: Capacity, Reliability, Safety, and Renewal </li></ul><ul><li>“ The central goal of the SHRP 2 Reliability focus area is to reduce non-recurring congestion and improve travel time reliability through incident reduction, management, response and mitigation. ” </li></ul><ul><li>Four theme areas within the Reliability Program: </li></ul><ul><ul><li>Data, Metrics, Analysis, and Decision Support </li></ul></ul><ul><ul><li>Institutional Change, Human Behavior, and Resource Needs </li></ul></ul><ul><ul><li>Incorporating Reliability in Planning, Programming, and Design </li></ul></ul><ul><ul><li>Fostering Innovation to Improve Travel Time Reliability </li></ul></ul>
    37. 37. <ul><li>Reliable System </li></ul><ul><ul><li>Requires that demand and supply be in balance </li></ul></ul><ul><ul><li>Currently, the demand vs. supply gap is widening </li></ul></ul><ul><li>Essential Keys to Future Success </li></ul><ul><ul><li>Demand is balanced with supply </li></ul></ul><ul><ul><li>Full integration (mode, function, jurisdiction, data) </li></ul></ul><ul><ul><li>User options maximized </li></ul></ul><ul><ul><li>Fee-for-service funding </li></ul></ul><ul><ul><li>User fees pay for better, more reliable supply (system integration and operations, as well as new capacity) </li></ul></ul><ul><li>It is not possible to accurately predict the future </li></ul><ul><li>It is possible to prepare for the future </li></ul>Concluding Thoughts