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
26
26
26
26
8 4 8 4
8 4 8 4
G=25 Y=5 R=30
G=35 Y=5 R=20
Time
#1
#2
EB Band
Time-Space Diagram One-way Street
26
26
26
26
8 4 8 4
8 4 8 4
G=25 Y=5 R=30
G=35 Y=5 R=20
Time
#1
#2
EB Band WB Band
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.
26
26
26
26
8 4 8 4
8 4 8 4
G=25 Y=5 R=30
G=35 Y=5 R=20
Time
Bandwidth and Offset
#1
#2
WB:18 sec
EB:15 sec
26
26
26
26
8 4 8 4
8 4 8 4
G=25 Y=5 R=30
G=35 Y=5 R=20
Time
Bandwidth and Offset
#1
#2
WB:18 sec
EB:15 sec
26
26
26
26
8 4 8 4
8 4 8 4
G=25 Y=5 R=30
G=35 Y=5 R=20
Time
Bandwidth and Offset
#1
#2
WB:18 sec
EB:30 sec
26
26
26
26
8 4 8 4
8 4 8 4
G=25 Y=5 R=30
G=35 Y=5 R=20
Time
Bandwidth and Offset
#1
#2
WB:30 sec
EB:30 sec
2
6
26
8 4
8 4 8 4
#1
#2
1
5
2
6
1
5
EB:20 sec
WB:8 sec
Bandwidth and Phase Sequence(Dual Leading)
2
6
26
8 4
8 4 8 4
#1
#2
1
5
2
6
1
5
EB:20 sec
WB:12 sec
Bandwidth and Phase Sequence(Dual Leading- Offset Adjustment)
2
6
26
8 4
8 4 8 4
#1
#2
1
5
2
6
1
5
EB:20 sec
WB:12 sec
Bandwidth and Phase Sequence(Lead-Lag)
2
6
26
8 4
8 4 8 4
#1
#2
1
5
2
6
1
5
EB:20 sec
WB:20 sec
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?