CHAPTER 5. SIMULATION RESULTS
is only useful for a low traffic density. When a low θ is used for a high traffic
density, the traffic lights would switch too fast (almost every second). This will
give poor results. More green time is needed at the Wetstraat and this can be done
by a higher θ. A higher θ will make it more difficult for the side-roads to get a
green light.
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5.3.4 Phase Controller
For the higher traffic densities it seems that small values for θ give unwanted
results. A very small θ will grant an green-request very fast. In combination with
a small value for φmin, the traffic lights will switch very fast. This problem is
solved for values of θ ≥ 20. The phase controller with θ = 20 and φmin = 1 gives
the wanted behaviour: short green times for the side-roads and longer green times
for the Wetstraat.
A higher φmin will result in a very high ATWT value. The reason is that the
side-roads get much longer green time than needed. This will stop the traffic flow
on the Wetstraat for too long, which will result in waiting queues for the Wetstraat.
Not only φmin specifies the green time, but also θ has an influence. Higher
values for θ will cause a longer waiting time before granting a request.
At low traffic density there is no problem for a low value of θ. From 20pm till
5am the best results are given for low values of θ and φmin.
At the highest traffic density (7am), a very high θ is needed. There are passing
5270 vehicles on the Wetstraat. The flow on the Wetstraat is a priority and the
green times for the Wetstraat should be as long as possible, without creating long
queues on the side-roads.
5.3.5 Platoon controller
The platoon controller works best for a low minimum green time (φmin) because
the traffic light stays green when a platoon is crossing the traffic light. The density
of a platoon can be defined with the parameters μ and ω.
A low minimal green time (φmin) with higher values of θ has a special con-
sequence, because the controller does not break platoons. When a queue of road