#define PIN_RED    2 // The Arduino pin connected to R pin of traffic light module
#define PIN_YELLOW 3 // The Arduino pin connected to Y pin of traffic light module
#define PIN_GREEN  4 // The Arduino pin connected to G pin of traffic light module

#define RED_TIME     2000 // RED time in millisecond
#define YELLOW_TIME  1000 // YELLOW time in millisecond
#define GREEN_TIME   2000 // GREEN time in millisecond

#define RED    0 // Index in array
#define YELLOW 2 // Index in array
#define GREEN  1 // Index in array

const int pins[]  = {PIN_RED, PIN_GREEN, PIN_YELLOW , };
const int times[] = {RED_TIME, YELLOW_TIME, GREEN_TIME};

void setup() {
  pinMode(PIN_RED, OUTPUT);
  pinMode(PIN_YELLOW, OUTPUT);
  pinMode(PIN_GREEN, OUTPUT);
}

// the loop function runs over and over again forever by using array
void loop() {
  for (int light = RED; light <= YELLOW; light ++) {
    trafic_light_on(light);
    delay(times[light]); // keep light on during a period of time
  }
}

void trafic_light_on(int light) {
  for (int i = RED; i <= YELLOW; i ++) {
    if (i == light)
      digitalWrite(pins[i], HIGH);   // turn on
    else
      digitalWrite(pins[i], LOW);   // turn off
  }
}