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: xinyu@hawaii.edu

Personal Website: www2.hawaii.edu/~xinyu