A Unique Approach for Arterial Bandwidth Optimization

Presenter: Md. Arafat Hossain KhanAdvisor: Dr. Zong Tian

Civil and Environmental EngineeringUniversity of Nevada, Reno

Outline

• Why Bandwidth Optimization• Research Goal• Background• Proposed Algorithm with Case Studies• Analysis

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Time-Space Diagram One-way Street

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Time-Space Diagram Two-way Street

Why Bandwidth Optimization

• Minimizes – Fuel consumption– Pollution emission – Stops – Queue length– Arrival of platoons at red lights

• Maximizes – Smooth flow– Capacity– Driver’s satisfaction

Research Goal

• The goal of the research is to optimize

– Phasing Sequence– Offset – Arterial Partition

First two factors are most important and visible.

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Bandwidth and Offset

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WB:18 sec

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Bandwidth and Offset

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WB:18 sec

EB:15 sec

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Bandwidth and Offset

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WB:18 sec

EB:30 sec

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Bandwidth and Offset

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WB:30 sec

EB:30 sec

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EB:20 sec

WB:8 sec

Bandwidth and Phase Sequence(Dual Leading)

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Bandwidth and Phase Sequence(Dual Leading- Offset Adjustment)

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Bandwidth and Phase Sequence(Lead-Lag)

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Bandwidth and Phase Sequence(Lead-Lag – Offset Optimization)

Background• W. D. Brooks, “Vehicular Traffic Control:

Designing Traffic Progression Using A Digital Computer”,1965.– Equal bandwidth requires a tradeoff between

attainability and bandwidth• C. J. Messer, R. N. Whitson, C. L. Dudek, and E.

J. Romano. “A Variable-Sequence Multiphase Progression Optimization Program”. 1973– Obtaining the maximum bandwidth for one

direction while ensuring partial bandwidth for the other direction

Background (Cont…)

• Zong Tian and Thomas Urbanik, “System Partition Technique to Improve Signal Coordination and Traffic Progression”, 2007– Heuristic approach

• Yi Zhao, Zong Tian, “Phasing Sequence and Signal Spacing Based Progression Bandwidth Optimization Technique”, 2012– Reformulation of Messer’s Algorithm

Background (Cont…)

• Wu Xianyu, Hu Peifeng and Yuan Zhenzhou, “Link-Based Signalized Arterial Progression Optimization with Practical Travel Speed”, 2013– Improved Messer’s Algorithm– Optimal coordinated signal timing plan with both

optimal link bandwidth and optimal arterial bandwidth

Proposed Algorithm – Main Idea

• Optimize each two intersections and proceed thereby for the whole arterial.

• For a very large number of intersections the method had the capability to do partition based on any predefined objective function (e.g. Attainability)

• Possible to hand calculate the whole arterial using simple geometry.

Assumptions – Proposed Method

• Vehicle speed is constant• Phase time is constant – Not actuated• No Trasition

Methodology with Case Study

Step – 1 : Optimize the phase sequence of first intersection

Step – 1 (Cont…)

• Lag – Lead is better

Step – 1 (Cont…)

• Dual Lead is better

Step – 1 (Cont…)

Step – 1 (Cont…)

Step – 2 : Offset and Phase Sequence of Second Intersection

• Adjust phase sequence according to the phase sequence of the first intersection

• Offset calculation is constrained under an ‘objective function’– Equal bandwidth– Priority based bandwidth• AM, PM peak hour priority• Arterial Priority

[ In our case – equal Bandwidth was considered ]

Step – 2 : Objective Function

• Arguments– Band projection after optimizing the phase

sequence of the first intersection– Phase time of the second intersection

• Return– The ratio of the inbound and outbound bandwidth

• The offset is calculated based on the return (ratio)

Step – 2 (Cont…)

Step – 2 (Cont…)

Step – 3 : Optimize Phase Sequence of Intersection #3

Step – 3 : Optimize Offset of Intersection #3

Step – 4 : Optimizing Phase Sequence and Offset - other Intersections

• Repeat Step 3 for the next intersection• Continue until all the phase sequences and

offsets of all the intersections are optimized

Optimizing Intersection # 4

Optimizing Intersection # 4

Optimizing Intersection # 5

Optimizing Intersection # 5

Eureka 100% attainability

Computational Complexity

• The method undergoes no iteration or trial and error method to determine the optimum phasing sequence and offset

• For partition the method still does not require any iteration

Extremely Fast

Synchro Optimization

Let Synchro optimize the arterial for us

Synchro Vs Proposed Method

• Faster (Using low level programming – not yet proved)

• Better (Already proved)

Close View of the Optimized Graph from Synchro and MATLAB

MATLAB

Synchro

Problems and Solutions

Problem: After optimizing the attainability may fall to a very low value.– Large number of intersections– Relationship between signal timing and

intersection distancesSolution: Partition Technique – Maintain the link bandwidth between the last

intersection of the nth partition and the first intersection of the (n+1)th partition

Objective function for Partition

• Distance• Travel time• Attainability• Combination of these

When the objective function falls below a ‘threshold’ the partition is done

Network Partition

• Based on ‘Priority Matrix’ – Segmented Arterials

• Proposed method cannot ensure good network progression

Some Supplementary Results

• For fixed travel speed, optimum phase sequence shows an oscillating behavior with the distance between two intersections.

• Offset carries the information of inbound and outbound priority

Conclusion

• The method is – Extremely fast– Flexible to set inbound and outbound priority– Flexible to incorporate partition very easily

• The method does not– Deal with delay– Ensure network bandwidth

Acknowledgement

Proper direction of my supervisor Dr. Zong Tian

Thank You !!

Questions?