Traffic Simulation & Optimization 2011.5.23 Hsuan Lee
References 1.A Cellular Automata Model for Highway Traffic. E.G. Campari and G. Levi. 2000 2.Two Lane Traffic Simulations Using Cellular Automata. M. Rickert, K. Nagel, M. Schreckenberg, A. Latour. 1995 3.Optimization of Traffic Lights at Crossroads. D. W. Huang and W. N. Huang. 2002 4.The Use of Genetic Algorithm for Traffic Light and Pedestrian Crossing Control. A. M. Turky, M. S. Ahmad and M. Z. M. Yusoff. 2009
Traffic Simulation The traffic of a road segment can be simulated with Cellular Automata (CA) 1.Composed of simple cells. 2.Each cell interact with neighbors according to a simple rule. 3.With a large number of cells, complex phenomena can be produced. Like Conways game of life
Single-Lane Simulation We have 1.A lane 2.Some cars 1.Position 2.Velocity (cells/tick) 3.Some rules for cars movements 1.IF v(i) < vmax THEN v(i) += a 2.IF v(i) > gap(i) THEN v(i) = gap(i) 3.IF v(i) > 0 THEN v(i) -= a2 (randomly) EvaluateMove
Multiple-Lane Simulation We have 1.Two lanes 2.Some more cars 1.Position 2.Velocity (cells/tick) 3.Some more rules for cars movements IF gap(i) lo IF gap,o,back(i) > lo,back THEN change lane (randomly) Evaluate Move sidewards Move forward
Traffic Flow Simulation Characteristics 1.Symmetry 2.Stochasticity 3.Backward Causality Rules for cars movements 1.IF v(i) < vmax THEN v(i) += a 2.IF v(i) > gap(i) THEN v(i) = gap(i) 3.IF v(i) > 0 THEN v(i) -= a2 (randomly) 4.IF gap(i) lo IF gap,o,back(i) > lo,back THEN change lane (randomly)
Traffic Flow Simulation With the CA model for traffic flow alone, traffic phenomena on road segments (without traffic lights) can be predicted and simulated. Highway traffic simulation
Crossroad Simulation We have 1.Two sets of bidirectional roads 2.Lane transition rules Each car has a direction in mind, if the car wants to turn right, it turns at the transition point 3.Traffic lights Before a car enters the red zone, it checks the traffic light.
Traffic Simulation & Optimization Finally, we have 1.A bunch of roads 2.A truck of intersections 3.Cars generated at some specific positions, with destinations and routes in their minds Average travel time can be evaluated as a fitness function when we adjust 1.Traffic light time 2.Lane width or lane allocation ( ) Suitable for hBOA or other GAs capable of solving problems with overlapped BBs
Final Word With the development of Internet of Things, traffic simulation and verification will become more mature. One day will come when all cars can be located through GPS. Routes can be decided automatically according to the current traffic status. Traffic optimization will be an important issue by then.