CHAPTER 5. SIMULATION RESULTS
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For lower traffic density, platoons are much more visible. On the side-roads,
only a few cars are waiting in front of a red traffic light. Those cars get green
faster, because there is less traffic on the Wetstraat. When the last car has past
the junction, the traffic light of the side-road stays green, until the cars on the
Wetstraat are approaching the traffic light and the conditions are met. This is how
platoons are formed. When a single car gets to a red light, it has to wait until the θ
has been reached. More cars are joining and the condition is reached faster. When
the traffic light turns to green, a group of cars can move together.
For the lowest traffic densities, a lower minimal green time (φmin) and a lower
θ is needed, otherwise cars have to wait in front of a traffic light, when there is no
traffic on the side-roads.
5.3.6 Best parameters for Platoon at highest traffic density.
For higher values of θ better results are given for lower φmin values, but when
φmin = 1 for a lower values of θ, the traffic lights do not show the expected
behaviour. Some scenarios are given below. The ATWT values for the Wetstraat
at 7am for the different parameters can be found in table 5.10.
• If the destination road behind the junction is full, the traffic lights switch at
maximum speed, depending on the φmin value. This is because when the
destination road is full, the cars that have to cross the junction will slow
down and the density of cars will rise. The second condition of the platoon
controller will not be satisfied and the request of the other road will be
accepted, but this road will have the same problem. This will cause the
switching at a speed depending on φmin. The problem is solved when the
road after the junction is creating some open space.
• If φmin = 1 and the threshold value θ can be reached within a few seconds, it
can happen that the traffic lights switch very fast and this will interleave the
traffic of the Wetstraat and its side-road. This will increase the queue of cars
in the side-roads, but the Wetstraat will decrease its waiting queue. Because
of this, the platoon controller with θ = 5 and φmin = 1 has a very low
average trip waiting time. The low ATWT is very nice, but the behaviour is