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 simulation/modeling Simtraffic VISSIM TransCAD EMME/2 Complex Algorithm Genetic algorithm (GA)-based 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 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://www2.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 Existing Movements of Downstream Approach Determinant of Arrival Capacity Downstream Arrival Capacity (veh/hr) Existing Arrival Volume (veh/hr) Queue Spillback Occurred? Left Turn YES 1830 1200 NO Through/Right Turn With Project Upstream Treatments Downstream Arrival Capacity (veh/hr) Design Capacity (veh/hr) Maximum Additional Upstream Arrival Spillback Occurred? and Capacity Loss (veh/hr) Underpass Lane 1830 1620 630 Yes, 990 At-grade Lane 600 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: www2.hawaii.edu/~xinyu