The Cell Transmission Model (CTM) is a numerical approximation of the shockwave theory.
The CTM divides the links into discrete segments, known as cells, and updates the density
of each cell (number of vehicles) after every second. Due to its simple formulations and highspeed
execution, the CTM is considered advantageous for model-based Adaptive Traffic
Control Systems (ATCSs). A CTM implementation was developed within Sitraffic Motion, the
“Motion-CTM” [9]. The “Extended Motion-CTM” [11] calculates two performance indices for
the online signal plan optimization in Sitraffic Motion: the number of stops and the waiting
time. The Extended Motion-CTM introduces a new variable for every cell in the network, the
Congestion Indicator ????????????????. The ???????? not only facilitates the calculation of the number of stops
and the waiting time, but also assigns the calculated values to the appropriate signal. The
significance of this novel idea is that it enables the calculation of signal related performance
indices for the whole network in each second. The development of the ???????? algorithm in the
form of a finite-state machine diagram is the core of this work. For the calculation of the
number of stops, the ???????? is utilized to identify the cells at the end of the queue. Based on the
outflow (vehicles per second) of these cells, the number of stops is derived. For the
calculation of the waiting time, the ???????? is utilized to identify the cells that are in the queue. The
waiting time is derived from the density of these cells and their outflow. The evaluation of the
proposed algorithms shows that both the derived number of stops and waiting time are very
close to the theoretical values obtained from the shockwave theory. Regarding the number
of stops, the evaluation shows that the proposed algorithms perform much better than the
approximation by Lin [10]. Regarding the waiting time, the evaluation shows that the delay
calculation based on Almasri [6] and the waiting time in the Extended Motion-CTM give very
similar results.
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The Cell Transmission Model (CTM) is a numerical approximation of the shockwave theory.
The CTM divides the links into discrete segments, known as cells, and updates the density
of each cell (number of vehicles) after every second. Due to its simple formulations and highspeed
execution, the CTM is considered advantageous for model-based Adaptive Traffic
Control Systems (ATCSs). A CTM implementation was developed within Sitraffic Motion, the
“Motion-CTM” [9]. The “Extended Motion-CTM” [11] c...
»