const int redPin = 12;    // Red light
const int yellowPin = 14; // Yellow light
const int greenPin =27;  // Green light

void setup() {
  pinMode(redPin, OUTPUT);
    pinMode(yellowPin, OUTPUT);
      pinMode(greenPin, OUTPUT);
      }

      void loop() {
        // Red light ON
          digitalWrite(redPin, HIGH);
            digitalWrite(yellowPin, LOW);
              digitalWrite(greenPin, LOW);
                delay(3000); // Wait 3 seconds

                  // Yellow light ON
                    digitalWrite(redPin, LOW);
                      digitalWrite(yellowPin, HIGH);
                        digitalWrite(greenPin, LOW);
                          delay(1000); // Wait 1 second

                            // Green light ON
                              digitalWrite(redPin, LOW);
                                digitalWrite(yellowPin, LOW);
                                  digitalWrite(greenPin, HIGH);
                                    delay(3000); // Wait 3 seconds
                                    }