Traffic Light Control
27
06/06/22 1 Traffic Light Control Hoàng Hải Lưu Như Hòa Department of Automatic Control Hanoi University of Technology
Transcript of Traffic Light Control
04/08/23 1
Traffic Light Control
Hoàng Hải
Lưu Như Hòa
Department of Automatic Control
Hanoi University of Technology
04/08/23 2
Overview
Improving safety Minimizing travel time Increasing the capacity
of infrastructures
The problem of transport system is an optimal problem control Main Goals are:
04/08/23 3
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 !!!
04/08/23 4
Modeling and Controlling Traffic
Section 1
04/08/23 Modeling and Controlling Traffic 5
Modeling and Controlling Traffic
Macroscopic scale: Similar to models of fluid dynamics
PDE
Microscopic scale: each vehicle is considered as an individual
ODE
How traffic can be modeled ?
04/08/23 Modeling and Controlling Traffic 6
Macroscopic models
Macroscopic models based on fluid dynamics model
Relation between: traffic flux, traffic density and velocity.
04/08/23 Modeling and Controlling Traffic 7
Macroscopic models
04/08/23 Modeling and Controlling Traffic 8
Microscopic models
Microscopic models focus on vehicles (position and velocity )
Cellular automaton (CA): discrete model Road Δx Time steps Δt Nagel-Schreckenberg
model
Stephen WolframCreator of CA
04/08/23 Modeling and Controlling Traffic 9
Microscopic models
Road Cell
111 110 101 100 011 010 001 000
1 0 1 1 1 0 0 0
Rule 10 2184 10111000If next state is available Then Move forwardsElse Stop
current pattern
new state for center cell
04/08/23 Modeling and Controlling Traffic 10
Microscopic models
Self-caused slowdown:
Stable "stop-waves“
Two stable states
04/08/23 11
Traffic Light Control System
Section 2
04/08/23 Traffic Light Control System 12
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
04/08/23 Traffic Light Control System 13
Driver Detector - Camera
Identification image Expensive Complex Traffic System
04/08/23 14
04/08/23 Traffic Light Control System 15
Driver Detector - Loop Detector
•Measure Inductive•Most popular•Cheap
04/08/23 Traffic Light Control System 16
Traffic Light Control System
Distributed System A set of intersections A set of connection
(roads) Traffic lights regulating Traffic lights are co-
operation
04/08/23 Traffic Light Control System 17
Traffic Control and Command Centre
In Thailand
04/08/23 Traffic Light Control System 18
Green Waves
Offset of cycle can be adjusted to create green waves.
04/08/23 19
Control Algorithms
Section 3
04/08/23 Control Algorithms 20
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 light-based expert systems
improve performance but much computation
Can Machines Think?
04/08/23 Control Algorithms 21
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).
04/08/23 Control Algorithms 22
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
04/08/23 Control Algorithms 23
Reinforcement Learning
how an agent take actions in an environment to maximize long-term reward
Thorpe used it for the traffic-light problem
04/08/23 Control Algorithms 24
Intelligent Agents
04/08/23 25
Conclusion
Modeling Macroscopic Model Microscopic Model
Traffic Control System Traffic light control in a junction Co-operation in traffic control system
Control Algorithms
04/08/23 26
References
http://en.wikipedia.org [Wiering,2004],Intelligent Traffic Light Control [Tan Kok Khiang,1997] Intelligent Traffic
Lights Control by Fuzzy Logic
04/08/23 27
Thank you for your attention!
