DOWNSTREAM QUEUES ON UPSTREAM CAPACITY EXPANSION AT URBAN
DOWNSTREAM QUEUES ON UPSTREAM CAPACITY EXPANSION AT URBAN SIGNALIZED INTERSECTIONS Xin (Alyx) Yu, E. I. T. University of Hawaii at Manoa Presented at the ITE Western District Annual Meeting June 25, 2012
Outlines �Problem �Solution �Application �Conclusion
PROBLEM
Downstream Spillback � Restricted upstream capacity � Deteriorating downstream traffic conditions
Existing Approaches � Traffic ü ü simulation/modeling Simtraffic VISSIM Trans. CAD EMME/2 � Complex Algorithm ü Genetic algorithm (GA)-based ü Macroscopic hypothetical model
Weaknesses of Existing Methods �Data-intensive or compute-intensive �Expensive to gather the data �Impractical for a project in the early stage of alternative screenings �Impractical for a minor/temporary project with a limited budget
So we need…… �A quick process to analyze downstream queuing effects � Using the basic and typically available data � Must be reliable and easy to use
SOLUTION
We have HCM…… � Investigate capacity constraint of downstream queues by reversing and integrating the HCM procedures of intersection capacity and queue length estimation HCM 2010: f (X, Y) = Z f(Arrival Rate (X) , Signal Timing (Y)) = Vehicle Queue Length (Z) Our method: f (Z, Y) = Y f(Max Allowable Queue Storage Length , Downstream Intersection Signal Timing) = Max Downstream Allowable Arrival Rate
Example: Is there queue spillback at EB downstream? Existing EB Downstream Entry Volume V. S. Max Downstream Allowable Arrival Rate. √ If less, no queue spillback and upstream capacity expansion is possible √ If greater or equal to, queue spillback will occur or is about to occur
Spreadsheet Tools � Developed using Microsoft Excel 2007 � A one page worksheet containing three sections: Inputs, Summary and Output. Download available at my personal website: http: //www 2. hawaii. edu/~xinyu (model tab)
APPLICATION
� Vineyard Blvd. and Punchbowl St. � Two capacity expansion options on the WB: 1. Underpass lane 2. At-grade lane
Analysis and Evaluation
Analysis and Evaluation Movements of Downstream Approach Determinant of Arrival Capacity Downstream Arrival Capacity (veh/hr) Left Turn Through/Right Turn YES NO 1830 Existing Arrival Volume (veh/hr) Queue Spillback Occurred? 1200 NO With Project Upstream Treatments Downstream Arrival Capacity (veh/hr) Design Capacity (veh/hr) Underpass Lane At-grade Lane 1830 1620 600 Maximum Additional Upstream Arrival Spillback Occurred? and Capacity Loss (veh/hr) 630 Yes, 990 No, 0
CONCLUSION
Conclusion � This process can answer: 1. Spillback occurrence (when and where) 2. The feasibility of intersection treatments (considering intersection interactions) � This process can be used in: 1. Project screening and planning level assessment 2. Developing a prioritized list of potential capacity expansion in urban corridor.
Questions and Comments Xin (Alyx) Yu, E. I. T. University of Hawaii at Manoa Email: xinyu@hawaii. edu Personal Website: www 2. hawaii. edu/~xinyu
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