A Novel Intelligent Traffic Light Control Scheme Cheng Hu, Yun Wang Presented by Yitian Gu

Objective Propose a novel control scheme, in which both the upstream and downstream information are taken into account and traffic light states are dynamically reasoned and adaptively adopt real-time traffic conditions To reduce average waiting time at a road cross

Results Proposed control scheme vs. fixed-time control First scenario: All upstream lanes have the same arrival rate

Results Proposed control scheme vs. fixed-time control Second scenario: arrival rates are all set to 0.35 at first, then increased according to a vector for n times Vector: (0.02, -0.01, -0.01, -0.02, 0.03, -0.01, 0.02, -0.01, -0.01, -0.02, 0.03, -0.01)

Outline III. Intelligent Traffic Light Control Scheme A.The Crossroad Model -Two-way, three lanes each direction, i.e. 12 upstream lanes and 12 downstream lanes -Each upstream L i with corresponding downstream lane L j together forms a serial lane, denoted by L ij -12 predefined states of a traffic light, each state s x allows vehicles in two serial lanes L ij and L mn to go through

Outline III. Intelligent Traffic Light Control Scheme A.The Crossroad Model B.The Control Scheme 1)Weight of a Serial Lane -Defines the weight function of a serial lane using both the upstream and downstream information including arrival rate, departure rate and spaces vacant -Basic idea is to choose the state which contains as many cars as possible in upstream, and as few cars as possible in downstream -Considers the Starvation problem 2)Selection and Duration of Traffic Light States -Selects the state that has the largest sum of weight -Each selected state has minimum green time t 0, if the state remains the same as the previous one, a time slice Δt is added.

Outline IV. Simulation and Analysis A.Effects of Arriving Rate First scenario: -Proposed scheme increases slower as the arrival rate increases -Comparatively, average waiting time of proposed scheme is around 1/3 of that of the fixed scheme Second scenario: -Given a fixed sum of arrival rates, the greater difference of the arrival rates, the more benefits of the intelligent control scheme

Outline IV. Simulation and Analysis B.Effects of Vehicle Speed, Vehicle Length, Vehicle Margin and Lane Length C.Effects of Minimum Green Light Duration -With the increase of minimum green time, the average waiting time increases D.Effects of Beta -When Beta increases, the average waiting time decreases

Outline V. Conclusion and Future Work Work has done: -Describe a road cross model -Propose an intelligent control scheme -Do simulations to explore scheme’s features -In general the average waiting time is significantly less than that of the fixed-time scheme Future work: -Take into account the influence of acceleration, pedestrian and etc. -Extend to control a traffic network

Control Scheme Weight of a Serial Lane n 0 : target vehicle number of lane L j when there is no congestion n(t) : current vehicle number of lane L j fin k : arrival rate of upstream lane L k fout j : departure rate of downstream lane L j P, Q : controllable parameters

Control Scheme Weight of a Serial Lane i.P is inversely proportional to Q ii.If a downstream is congested, the current traffic status has more effects iii.If a downstream is empty, the historical status has more effects P and Q : k : current queue length K : queue capacity

Control Scheme Weight of a Serial Lane Problem: State Starvation If some serial lane’s upstream is always low arrival rate and its downstream is always full, certain traffic light states may not be tuned for a long time Solution: Ageing function t 0 : the minimum green time β : a positive real number Final weight of a serial lane:

Control Scheme Selection and Duration of Traffic Light States Each state s i contains two serial lanes L mn and L pq with their final weights w mn and w pq, thus s i is assigned W i = w mn + w pq When the duration of state s(t) comes to an end, a new state is launched, which holds the largest value among those of all the serial lanes at present. i.e. If s ( t +1) = s ( t ), a time slice Δt is added to the current state’s duration Otherwise, the current state is switched to s(t+1), and its duration is set to t 0

Reference Cheng Hu and Yun Wang, “A Novel Intelligent Traffic Light Control Scheme,” in th International Conference on Grid and Cooperative Computing (GCC), 2010, pp. 372–376.

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