With the rapid increase in the urban population, the demand for the secure, reliable and intelligent public transportation system has also increased. The conventional public transportation systems lack real-time monitoring, auto safety, and proper communication with transport authorities. To address these issues, this paper presents an Internet of Things (IoT)-based Smart Public Transportation System. The proposed system utilizes an Arduino Mega 2560 microcontroller along with a set of sensors to monitor environmental conditions, passenger safety parameters and vehicle conditions. Temperature and humidity inside the vehicle are monitored using DHT11 sensor, obstacle detection using ultrasonic sensor and alcohol detection MQ-3 sensor to prevent alcohol-impaired driving. Additional modules such as GPS unit enable real-time positioning, and cloud-based data transmission and emergency messaging using GSM and IoT modules. Output devices like LCD display, buzzer and relay-operated motor provide local alerts and automated control actions. The proposed system is a scalable and cost-effective solution for the modern smart transportation system as it improves operational efficiency, passenger safety and facilitates remote monitoring by the transport authority.