Development of a Smart Traffic Light Control System with Adaptive Timing Using a Siemens PLC Training Kit

Fixed-time traffic signals cannot respond to changing traffic demand and often waste green time. This paper presents a smart traffic light controller with adaptive green-time extension designed for a Siemens PLC training kit and evaluated by simulation. Vehicle presence is detected by sensors, and the program adjusts the green interval within minimum and maximum limits while respecting yellow and all-red clearance intervals and a safe fault mode. The behavior is compared with a fixed-time plan for several simulated traffic scenarios. In simulation the adaptive controller reduced the mean waiting time per vehicle by 49 % (low), 29 % (medium) and 45 % (high demand) compared with a fixed 25 s plan.