Capacity and the Breakdown Phenomenon at a Freeway

Capacity and the Breakdown Phenomenon at a Freeway Merge Bottleneck: Unlocking the Potential of Loop Sensor Data Robert L. Bertini Department of Civil & Environmental Engineering Portland State University February 22, 2002

Outline • • Introduction Previous Studies Method Data Results Summary Implications Ongoing and Future Research “Let Knowledge Serve the City” 2

Introduction • Research Question – Empirically examine evolution of traffic from free flow to queued conditions at a freeway bottleneck downstream of a merge. • Exciting Opportunity – Bottlenecks are critical nodes in system. – First sixty years: » Promising theories (e. g. , Lighthill-Whitham-Richards, Edie, Newell) needed validation. » Difficult to collect data. » Fundamental uncertainties. – Today: » Sensor-rich, “too much” data » Understand traffic behavior » Building blocks for proposing/validating models “Let Knowledge Serve the City” 3

Research Implications • Understand traffic behavior at a merge. • Demonstrate benefits of traffic management sensor investment for research. • Reveal benefits of archived raw data. • Method for unequivocally pinpointing active bottleneck. • Resolve two-capacity issue. • Potential for future research: – Improve macroscopic models. – Assess ramp metering. – Enhance freeway management. – Update design standards. “Let Knowledge Serve the City” 4

Active Bottleneck • Discharging from upstream queue (maximum). • Not impeded by downstream effects. “Let Knowledge Serve the City” 5

Previous Studies • Data from fixed points – Bivariate plots – Scatter plots • Time dependencies & statistical fluctuations – Short time intervals – Long time intervals “Let Knowledge Serve the City” 6

Method N(x, t) Flow Time, t @ x “Let Knowledge Serve the City” 7

Method “Let Knowledge Serve the City” 8

Method “Let Knowledge Serve the City” 9

Cumulative Curves “Let Knowledge Serve the City” 10

Skewed Cumulative Curves “Let Knowledge Serve the City” 11

Site – Gardiner Expressway “Let Knowledge Serve the City” 12

Occupancy Data “Let Knowledge Serve the City” 13

Loop Sensor Data Validation “Let Knowledge Serve the City” 14

Loop Sensor Data Validation “Let Knowledge Serve the City” 15

Pinpointing the Bottleneck “Let Knowledge Serve the City” 16

Queue Presence “Let Knowledge Serve the City” 17

Bottleneck Deactiviation “Let Knowledge Serve the City” 18

Estimating Bottleneck Capacity “Let Knowledge Serve the City” 19

Reproducibility “Let Knowledge Serve the City” 20

Active Bottleneck Under Different Conditions “Let Knowledge Serve the City” 21

Reproducible “Let Knowledge Serve the City” 22

Precursors to Breakdown “Let Knowledge Serve the City” 23

Summary • • • Benefits from applying method to archived sensor data. Bottleneck location fixed: 1 km downstream of ramp. Resolved two-capacity issue: high flow prior to queue formation. Tell-tale breakdown signal. Measured capacity: average discharge flow. “Let Knowledge Serve the City” 24

Conclusions • • Importance of bottlenecks. Robust method. Greater understanding of merge bottlenecks. Contributions: – Empirical approach. – Metering, managing and modeling. – ATIS, ATMS, and ADUS “Let Knowledge Serve the City” 25

Ongoing Research • Toronto merge trajectories • Lane drop bottleneck – London – Minneapolis – Other bottlenecks “Let Knowledge Serve the City” 26

Ongoing Research “Let Knowledge Serve the City” 27

Example Projects Using Archived ITS Data for Transportation Performance Measures Oregon Department of Transportation • Portland Advanced Traffic Management System (Trans. Port) – – 90 ramp meters 400 inductive loop detectors 49 CCTV cameras 13 variable message signs • Using archived data to demonstrate value of archiving, and expanding possibilities for generating information useful for planners, engineers, policymakers and ultimately the users via ATIS • Monica Leal, MS Student “Let Knowledge Serve the City” 28

Example Projects Using Archived Data to Measure Operational Benefits of Intelligent Transportation System Investments U. S. Department of Transportation (Trans. Now) and ODOT • Use existing data, surveillance and communications infrastructure • Two case study evaluations for Oregon – COMET incident management program – Portland ramp metering system. • Set precedent for future evaluations of ITS programs. “Let Knowledge Serve the City” 29

Example Projects Alternatives to Motor Fuel Tax Oregon Department of Transportation • Collaboration with Professor T. Rufolo, Urban and Regional Planning • Fuel tax revenue declining with fuel efficient/alternative fuel vehicles • Other road finance measures under consideration • Consider fee based on vehicle miles traveled • Three goals of this phase: – Validate alternative financing mechanisms – Evaluate technologies for assessing alternative fees – Consider transition issues to new system – Minimize equity concerns “Let Knowledge Serve the City” 30

Example Projects Evaluation of Rural/Urban Incident Response Programs Oregon Department of Transportation Region 2 • Highway 18 and I-5 • Using archived data to measure effectiveness of existing program and assist ODOT in decisionmaking for future expansion of program to additional highway routes. “Let Knowledge Serve the City” 31

Example Projects Prototype for Advanced Public Transit Systems in Multimodal Corridor Great Cities Universities Coalition: Federal Transit Administration • Multi-disciplinary/multi-university team: • PSU Civil Engineering • PSU Urban Studies • City College of New York/City University of New York • Northwestern University • University of Alabama, Birmingham • Interstate 5/Barbur Blvd. Corridor • Testing strategies for improving transit operations and passenger information systems “Let Knowledge Serve the City” 32

Example Projects Using Transit Vehicles as Traffic Probes Tri-Met “Let Knowledge Serve the City” 33

Example Proposal Creating Safe and Sustainable Neighborhoods for Pedestrians and Bicyclists A Great City: Great University Partnership • • PSU Civil Engineering PSU Urban Studies and Planning OHSU Department of Emergency Medicine PSU School of Community Health • City of Portland • Multnomah County EMS • Oregon Department of Health Services • Oregon State Police • Tri-Met • Tualatin Valley Fire and Rescue • Willamette Pedestrian Coalition “Let Knowledge Serve the City” 34

New Potential Project Integrated E 911/Emergency Response/Transportation Network • Oregon Testbed: First demonstration in the nation • Partnerships: Intel, Senator Wyden, Comcare Alliance, EMS, 911, Transportation Agencies, PSU “Let Knowledge Serve the City” 35

Vision for Real-Time Traffic Management Center “Let Knowledge Serve the City” 36

Conclusion Thank You! “Let Knowledge Serve the City” 37