An Analytical Framework for Managed Lane Facility Performance Evaluation

1. An Analytical Framework for Managed Lane Facility Performance Evaluation Xiaoyue Cathy Liu University of Washington To Be Presented at the Western ITE Annual Meeting in Santa Barbara, CA June 26th, 2012

2. Outline General Background Methodological Framework Cross-Weave Module Friction Module Summary

3. Project Overview – Why Managed Lanes? • Congestion • A total urban congestion cost of $101 billion and total delay hours of 4.8 billion hours in 2010 • Vehicle Miles Traveled vs. Roadway Capacity Increase • Limited Infrastructure Expansion Capability

4. Background • NCHRP 03-96 Project: Analysis of Managed Lanes on Freeway Facilities • A methodological framework is needed for analyzing freeway facilities with ML and GP lanes operated parallelly • Composition and behavior characteristics difference • Interaction between the two lane groups

5. Managed Lane Characteristics Image: SR 91 Express Lanes • Operational Strategy: HOV vs. HOT • Separation Type • Barrier • Buffer • Stripe Image: I-394 MnPass WA SR 167 HOT

6. Managed Lane Access The most common ML type is left-concurrent

7. Single vs. Multiple Lanes Single ML Lane – Inability to pass slow lead vehicle

8. Single vs. Multiple Lanes Two ML Lanes – Ability to pass slow lead vehicles

9. Types of Interaction Between GP and MLs • Friction Effect - between Adjacent GP and Basic Segments • Poorly-operating GP lanes will have an adverse effect on the operations of the adjacent ML due to their proximity • Due to the proximity of GPL and ML traffic, increasing congestion levels on GPLs are proved to have an adverse effect on ML operations, well before the ML demand reaches breakdown levels • This effect is particularly significant at single lane buffer-separated ML facilities

10. Frictional Effect

11. Types of Interaction Between GP and MLs • Cross Weaving Effect – at ML On/Off Ramp Segments • Cross-weaving flows between a GP lane ramp and ML access may affect GP capacity and speed

12. Components of the Proposed Method • Method builds upon HCM2010 Freeway Facilities Chapter • But several changes are needed • Developing managed lane segment types • New speed-flow relationships in the Managed Lanes, including frictional impact of congestion levels in the GP lanes on ML operations • Cross-Weave effects across GP lanes • Implementation to occur in FREEVAL Computational Engine

13. Proposed Methodology

14. Segment Types for Speed-Flow Curves

15. Quantifying Frictional Effect

16. Quantifying Cross-Weave Effect

17. Results Analysis

18. Capacity Adjustment/Reduction Factor

19. CRF Regression where CW is the cross-weave flow measured in vph, Lcw-min is the length from the ramp gore to the beginning of BOA measured in ft, and number of GP lanes ranging from 2 to 4

20. Computational Engine: FREEVAL-ML Build on FREEVAL-2010 Allow analysis of parallel GP and ML facility with common lane groups Development of aggregated and comparative performance measures

22. Summary A methodological framework is developed for analyzing freeway facilities with ML and GP lanes operated parallelly New modules incorporated in the analysis framework, such as friction module and cross-weave module are quantified via empirical research The computational engine is able to evaluate the parallel ML facilities and provide performance assessment to the users