Investigate the complexity of the control system of the Norwegian traffic light using Petri net model

Abstract

The Norwegian traffic light is more complicated than the traffic signals of the standard type that applies three colors of signals. The sequence of the standard type is green, yellow/amber, red, and return to the green signal as the initial state becomes a cycle of a traffic light. The Norwegian traffic light has one more stage, i.e., red-yellow that lights simultaneously. This fourth stage suggests the driver should be prepared to start driving. This state is at the end of the red signal. The implementation of the Norwegian traffic light at real-world can reduce the time delay of traveling although we apply it without using seven-segments as the countdown of timer stop remaining. The modification of the Norwegian traffic light changes the fourth stage into a light yellow color only. This paper aims to investigate the structural complexity of the control system using its Petri net model. We use simulation and invariants as the method of validation and verification of the traffic light model. The structural complexity of the Norwegian traffic light control system is the highest and the second is its modification. The standard system is the lowest. The algorithm for calculating the structural complexity uses the backward and forward incidence matrix of the Petri net model.