Traffic Light Control
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Traffic Light Control
Hoàng Hải Lưu Như Hòa Department of Automatic Control Hanoi University of Technology
11/19/08
1
Overview The problem of transport system is an optimal problem control Main Goals are:
Improving safety Minimizing travel time Increasing the capacity of infrastructures
11/19/08
2
Outline
Section 1: How traffic can be modeled ? Section 2: What a traffic light control system contain ? Section 3: New approaches to traffic light control !!!
11/19/08
3
Modeling and Controlling Traffic Section 1
11/19/08
4
Modeling and Controlling Traffic How traffic can be modeled ?
Macroscopic scale: Similar to models of fluid dynamics PDE
11/19/08
Microscopic scale: each vehicle is considered as an individual ODE
Modeling and Controlling Traffic
5
Macroscopic models
Macroscopic models based on fluid dynamics model Relation between: traffic flux, traffic density and velocity.
11/19/08
Modeling and Controlling Traffic
6
Macroscopic models
11/19/08
Modeling and Controlling Traffic
7
Microscopic models
Microscopic models focus on vehicles (position and velocity ) Cellular automaton (CA): discrete model
Road Δx Time steps Δt Nagel-Schreckenberg model
11/19/08
Modeling and Controlling Traffic
Stephen Wolfram Creator of CA
8
Microscopic models Road Cell
Rule
18410 101110002
current pattern new state for center cell
11/19/08
If next state is available Then Move forwards Else Stop
111 110 101 100 011 010 001 000 1 0 1 1 1 0 0 0 Modeling and Controlling Traffic
9
Microscopic models
Self-caused slowdown:
Stable "stop-waves“
Two stable states
11/19/08
Modeling and Controlling Traffic
10
Traffic Light Control System
Section 2
11/19/08
11
Traffic Light Control System
No obvious optimal solution In practice most traffic lights are controlled by fixed-cycle controllers Fixed controllers need manual changes to adapted specific situation
11/19/08
Traffic Light Control System
12
Driver Detector - Camera
Identification image Expensive Complex Traffic System
11/19/08
Traffic Light Control System
13
11/19/08
14
Driver Detector - Loop Detector •Measure Inductive •Most popular •Cheap
11/19/08
Traffic Light Control System
15
Traffic Light Control System
Distributed System
A set of intersections A set of connection (roads) Traffic lights regulating Traffic lights are cooperation
11/19/08
Traffic Light Control System
16
Traffic Control and Command Centre In Thailand
11/19/08
Traffic Light Control System
17
Green Waves
Offset of cycle can be adjusted to create green waves.
11/19/08
Traffic Light Control System
18
Control Algorithms
Section 3
11/19/08
19
Expert Systems
uses a set of given rules to decide upon the next action (change some of the control parameters) Findler,Stapp,1992 describe a network of roads connected by traffic lightbased expert systems improve performance but much computation
11/19/08
Control Algorithms
Can Machines Think?
20
Evolutionary Algorithms
Taaleetal,1998 using evolutionary algorithms to evolve a traffic light controller for a single intersection Result:
Generates green times for next switching schedule. Minimization of total delay / number of stops. Better results (3 – 5%) / higher flexibility than with traditional controllers. Dynamic optimization, depending on actual traffic (measured by control loops).
11/19/08
Control Algorithms
21
Fuzzy Logic
Passed through 31% more cars Average waiting time shorter by 5% Performance also measure 72% higher. In comparison with a human expert the fuzzy controller passed through 14% more cars with 14% shorter waiting time and 36% higher performance index
11/19/08
Control Algorithms
22
Reinforcement Learning
how an agent take actions in an environment to maximize long-term reward Thorpe used it for the traffic-light problem
11/19/08
Control Algorithms
23
Intelligent Agents
11/19/08
Control Algorithms
24
Conclusion Modeling
Macroscopic Model Microscopic Model
Traffic Control System
Traffic light control in a junction Co-operation in traffic control system
Control Algorithms
11/19/08
25
References
http://en.wikipedia.org [Wiering,2004],Intelligent Traffic Light Control [Tan Kok Khiang,1997] Intelligent Traffic Lights Control by Fuzzy Logic
11/19/08
26
Thank you for your attention!
11/19/08
27
Hoàng Hải Lưu Như Hòa Department of Automatic Control Hanoi University of Technology
11/19/08
1
Overview The problem of transport system is an optimal problem control Main Goals are:
Improving safety Minimizing travel time Increasing the capacity of infrastructures
11/19/08
2
Outline
Section 1: How traffic can be modeled ? Section 2: What a traffic light control system contain ? Section 3: New approaches to traffic light control !!!
11/19/08
3
Modeling and Controlling Traffic Section 1
11/19/08
4
Modeling and Controlling Traffic How traffic can be modeled ?
Macroscopic scale: Similar to models of fluid dynamics PDE
11/19/08
Microscopic scale: each vehicle is considered as an individual ODE
Modeling and Controlling Traffic
5
Macroscopic models
Macroscopic models based on fluid dynamics model Relation between: traffic flux, traffic density and velocity.
11/19/08
Modeling and Controlling Traffic
6
Macroscopic models
11/19/08
Modeling and Controlling Traffic
7
Microscopic models
Microscopic models focus on vehicles (position and velocity ) Cellular automaton (CA): discrete model
Road Δx Time steps Δt Nagel-Schreckenberg model
11/19/08
Modeling and Controlling Traffic
Stephen Wolfram Creator of CA
8
Microscopic models Road Cell
Rule
18410 101110002
current pattern new state for center cell
11/19/08
If next state is available Then Move forwards Else Stop
111 110 101 100 011 010 001 000 1 0 1 1 1 0 0 0 Modeling and Controlling Traffic
9
Microscopic models
Self-caused slowdown:
Stable "stop-waves“
Two stable states
11/19/08
Modeling and Controlling Traffic
10
Traffic Light Control System
Section 2
11/19/08
11
Traffic Light Control System
No obvious optimal solution In practice most traffic lights are controlled by fixed-cycle controllers Fixed controllers need manual changes to adapted specific situation
11/19/08
Traffic Light Control System
12
Driver Detector - Camera
Identification image Expensive Complex Traffic System
11/19/08
Traffic Light Control System
13
11/19/08
14
Driver Detector - Loop Detector •Measure Inductive •Most popular •Cheap
11/19/08
Traffic Light Control System
15
Traffic Light Control System
Distributed System
A set of intersections A set of connection (roads) Traffic lights regulating Traffic lights are cooperation
11/19/08
Traffic Light Control System
16
Traffic Control and Command Centre In Thailand
11/19/08
Traffic Light Control System
17
Green Waves
Offset of cycle can be adjusted to create green waves.
11/19/08
Traffic Light Control System
18
Control Algorithms
Section 3
11/19/08
19
Expert Systems
uses a set of given rules to decide upon the next action (change some of the control parameters) Findler,Stapp,1992 describe a network of roads connected by traffic lightbased expert systems improve performance but much computation
11/19/08
Control Algorithms
Can Machines Think?
20
Evolutionary Algorithms
Taaleetal,1998 using evolutionary algorithms to evolve a traffic light controller for a single intersection Result:
Generates green times for next switching schedule. Minimization of total delay / number of stops. Better results (3 – 5%) / higher flexibility than with traditional controllers. Dynamic optimization, depending on actual traffic (measured by control loops).
11/19/08
Control Algorithms
21
Fuzzy Logic
Passed through 31% more cars Average waiting time shorter by 5% Performance also measure 72% higher. In comparison with a human expert the fuzzy controller passed through 14% more cars with 14% shorter waiting time and 36% higher performance index
11/19/08
Control Algorithms
22
Reinforcement Learning
how an agent take actions in an environment to maximize long-term reward Thorpe used it for the traffic-light problem
11/19/08
Control Algorithms
23
Intelligent Agents
11/19/08
Control Algorithms
24
Conclusion Modeling
Macroscopic Model Microscopic Model
Traffic Control System
Traffic light control in a junction Co-operation in traffic control system
Control Algorithms
11/19/08
25
References
http://en.wikipedia.org [Wiering,2004],Intelligent Traffic Light Control [Tan Kok Khiang,1997] Intelligent Traffic Lights Control by Fuzzy Logic
11/19/08
26
Thank you for your attention!
11/19/08
27
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