1. 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

2. Outlines
Problem
Solution
Application
Conclusion

3. PROBLEM

4. Downstream Spillback Restricted upstream capacity
Deteriorating downstream traffic conditions

5. Existing Approaches Traffic simulation/modeling Simtraffic VISSIM
TransCAD
EMME/2
Complex Algorithm
Genetic algorithm (GA)-based
Macroscopic hypothetical model

6. 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

7. 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

8. SOLUTION

9. 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

10. 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

11. Spreadsheet Tools Developed using Microsoft Excel 2007
A one page worksheet containing three sections: Inputs, Summary and Output.
Download available at my personal website: (model tab)

12. APPLICATION

13. Vineyard Blvd. and Punchbowl St.
Two capacity expansion options on the WB:
1. Underpass lane 2. At-grade lane

14. Analysis and Evaluation

15. 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

16. CONCLUSION

17. 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.

18. Questions and Comments
Xin (Alyx) Yu, E.I.T. University of Hawaii at Manoa Personal Website: www2.hawaii.edu/~xinyu