SHRP 2 Project L08: Incorporation of Travel Time Reliability into the Highway Capacity Manual

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L38 Discussion - August 1, 2012

Research ObjectivesResearch Objectives

(1) Determine how non-recurrent congestion impacts can be incorporated into HCM procedures

(2) Develop methodologies to predict travel time reliability on freeway and urban street facilities

(3) Prepare draft material (Reliability Guide) for possible future incorporation into the HCM

The objectives of Project L08 are to:

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Anticipated ProductsAnticipated Products

• Computational procedures (and computational engines) for assessing travel time reliability– Freeway facilities– Urban streets

• Reliability Guidebook

• Draft chapters for possible inclusion in the HCM

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Guidebook OutlineGuidebook Outline

• Introduction– Purpose, importance, chapter organization– Definitions and concepts– Overview of the methodology

• Concepts– Objectives for Reliability Analysis– Measures of Effectiveness– Reliability Values for Major Metropolitan Areas– Data Acquisition Challenges– Interpretation of Results

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Guidebook Outline (part 2)Guidebook Outline (part 2)

• Methodology (overview of theoretical framework)

– Freeways – Urban Streets– Corridors

• Application (detailed description of computational steps)

– Freeways – Urban Streets– Corridors

• Use Cases– Freeway, Urban Street, Corridor

• References

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Appendices to GuidebookAppendices to Guidebook

• Scenario Generation• Recurring Demand Variability• Weather Effects• Incident Effects• Work Zone Effects• Special Event Effects• Computational Engine Documentation• Additional Example Problems• References

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Definitions and ConceptsDefinitions and Concepts

StudyPeriod

Study  Section

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Each cell is one analysis period of an analysis segment.

TemporalDimension

SpatialDimension

Reliability Reporting Period

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FrameworkFramework

• Flow Chart

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Use Cases for SHRP2-L08/HCMUse Cases for SHRP2-L08/HCM

1. Assess existing reliability of facilities. √2. Predict future reliability of facilities. √3. Identify options to improve reliability.4. Estimate benefits of improvements. √5. Prioritize reliability improvement options.6. Set local standards for acceptable reliability. √7. Improve demand modeling.

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Example Urban Street applicationsExample Urban Street applications

• Alternatives Analysis– Compare base condition to alternative condition

• Analysis Scenarios– Work zones and special events

• Alternative start dates and durations• Alternative lane closures and signal timing strategies

– Weather• Examine operational effects of strategies that reduce weather-

related crashes or crash severity (i.e., snow removal, resurfacing)– Incidents

• Examine operational effects of strategies that reduce incident duration

• Evaluate benefit of providing shoulder for stalled vehicle refuge– Design or Operation

• Evaluate alternative signal timing plans• Evaluate alternative intersection lane allocations or segment

geometry

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Combined Operation and Safety EvaluationCombined Operation and Safety Evaluation

• Consideration of Operations and Safety– Effect of design and control choices can be quantified

• Effect on operational performance• Effect on safety performance

– HSM makes combined, quantitative assessment possible

Urban Streets Reliability EngineUrban Streets Reliability Engine

• Welcome

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Step 1. Scenario GenerationStep 1. Scenario Generation

• Set Up

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Step 1. Scenario GenerationStep 1. Scenario Generation

• Set Up

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Step 3. Performance SummaryStep 3. Performance Summary

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Questions/DiscussionQuestions/Discussion

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