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
CTH = 1,600 Veh/h
CTH = 1,200 Veh/h
2,000 Veh/h
Q=400 Veh/h Q=400 Veh/h
A BBefore Capacity Expansion
1,600 Veh/h
CTH = 2,000 Veh/h
CTH = 1,200 Veh/h
2,000 Veh/h
Q=0 Veh/h Q=800 Veh/h
A B
2,000 Veh/h
CTH = 1,800 Veh/h
CTH = 1,200 Veh/h
2,000 Veh/h
Q=200 Veh/h Q=600 Veh/h
A B
1,800 Veh/h
N
1,200 Veh/h
1,200 Veh/h
1,200 Veh/h
After Capacity Expansion(Theoretical Condition)
After Capacity Expansion(Practical Condition)
CTH: Capacity of Eastbound Through Movement; Q: Queue Size
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?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
Subject Intersection
Downstream Intersection
-Entry Movements
-Downstream Segment
Spreadsheet Tools Developed using
Microsoft Excel 2007
A one page worksheet containing three sections: Inputs, Summary and Output.
Downstream Intersection
Analyzed by: Project:
Date and Time: Agency or Organization:
InputsA. Downstream Intersection Condition UnitsPosted Speed Limit mi/hr 25Distance to Upstream Int (D) ft 900Estimated Cycle Length (C) sec 120 0.7
B. Lane configuration and Signal TimingSelect Lane Group (LG) - NA TH RT NANo. of Lanes - 1 1Saturation flow veh/s/ln 0.48 0.45% LG Vol in Total Approaching Vol (Pi) - 0.80 0.20Effective Green (g) sec 84 84Arrival Type - 3 3
SummaryAvg. Approach Speed (Sa) mi/hr 34Acc/Dec Delay (da) sec 10Veh Spacing in Queue (Lv) ft 25Max Back-of-Queue Size (Q ) veh 37
Lane Group (LG) - NA TH RT NA% Veh Arriving on Green (P) - 0.7000 0.70Cyclic or Sustained Spillback - Sustained SustainedMax. Arrival Rate to LG (qi) veh/s/ln 0.35 0.33
0.44 1.66
Order of Spillback Occurrence - 1 2 Determinant Lane Group - YES NO
Output
veh/h
Location:
Downstream Arrival Capacity(Rounded to the nearest 5) 1585
Downstream Capacity Constraint Calculation Worksheet
Test Example Test Example
Xin Yu Test Example
23-Jul-11 University of Hawaii
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
S. Vineyard Blvd
Pu
nch
bo
wl S
t
Queen Emma St
H-1 F
reeway
N
Subject IntersectionSubject Intersection
WB Downstream Intersection
WB Downstream Intersection
EB Freeway On-rampEB Freeway On-ramp
WB Downstream Approach
WB Downstream Approach
Analysis and EvaluationInputsA. Downstream Intersection Condition UnitsPosted Speed Limit mi/hr 30Distance to Upstream Int (D) ft 635Estimated Cycle Length (C) sec 160
B. Lane configuration and Signal TimingSelect Lane Group (LG) - TH+RT TH LT NANo. of Lanes - 1 2 1Saturation flow veh/s/ln 0.45 0.45 0.45% LG Vol in Total Approaching Vol (Pi) - 0.22 0.60 0.18Effective Green (g) sec 80 80 22Arrival Type - 4 4 4
SummaryAvg. Approach Speed (Sa) mi/hr 36Acc/Dec Delay (da) sec 10Veh Spacing in Queue (Lv) ft 25Max Back-of-Queue Size (Q ) veh 26.4
Lane Group (LG) - TH+RT TH LT NA% Veh Arriving on Green (P) - 0.67 0.6667 0.18Cyclic or Sustained Spillback - Cyclic Cyclic SustainedMax. Arrival Rate to LG (qi) veh/s/ln 0.22 0.22 0.09
1.02 0.75 0.51
Order of Spillback Occurrence - 3 2 1 Determinant Lane Group - NO NO YES
Output
veh/hDownstream Arrival Capacity
(Rounded to the nearest 5) 1830
Analysis and Evaluation
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 NO
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, 990At-grade Lane 600 630 No, 0
Existing
With Project
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: [email protected]
Personal Website: www2.hawaii.edu/~xinyu