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 Li with corresponding downstream lane Lj
together forms a serial lane, denoted by Lij
12 predefined states of a traffic light, each state sx allows
vehicles in two serial lanes Lij and Lmn 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 t0, 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
Effects of Minimum Green Light Duration
C.
-
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
n0: target vehicle number of lane Lj when there is no congestion
n(t): current vehicle number of lane Lj
fink: arrival rate of upstream lane Lk
foutj: departure rate of downstream lane Lj
P, Q: controllable parameters
Control Scheme
• Weight of a Serial Lane
P and Q:
k: current queue length
K: queue capacity
i.
ii.
iii.
P is inversely proportional to Q
If a downstream is congested, the current traffic status has more
effects
If a downstream is empty, the historical status has more effects
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
t0: 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 si contains two serial lanes Lmn and Lpq with their final weights
wmn and wpq, thus si is assigned Wi = wmn + wpq
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 t0
Reference
Cheng Hu and Yun Wang, “A Novel Intelligent Traffic Light Control Scheme,” in
2010 9th International Conference on Grid and Cooperative Computing (GCC),
2010, pp. 372–376.
The End