#define RED_LED 18
#define YELLOW_LED 19
#define GREEN_LED 21
#define VEHICLE_SENSOR 22
#define BUZZER 23

void setup() {
    pinMode(RED_LED, OUTPUT);
    pinMode(YELLOW_LED, OUTPUT);
    pinMode(GREEN_LED, OUTPUT);
    pinMode(VEHICLE_SENSOR, INPUT_PULLUP);
    pinMode(BUZZER, OUTPUT);
}

void loop() {
    int vehicleDetected = digitalRead(VEHICLE_SENSOR);

    if (vehicleDetected == LOW) {
        // If vehicle is detected, prioritize Green Light
        digitalWrite(RED_LED, LOW);
        digitalWrite(YELLOW_LED, LOW);
        digitalWrite(GREEN_LED, HIGH);
        delay(5000);
    } else {
        // Normal Traffic Light Sequence
        digitalWrite(GREEN_LED, LOW);
        digitalWrite(YELLOW_LED, LOW);
        digitalWrite(RED_LED, HIGH);
        delay(5000);

        digitalWrite(RED_LED, LOW);
        digitalWrite(YELLOW_LED, HIGH);
        delay(2000);

        digitalWrite(YELLOW_LED, LOW);
        digitalWrite(GREEN_LED, HIGH);
        delay(5000);
    }

    // Emergency Buzzer for Pedestrian Safety
    if (vehicleDetected == LOW) {
        digitalWrite(BUZZER, HIGH);
        delay(1000);
        digitalWrite(BUZZER, LOW);
    }
}