void setup()   {
   pinMode(11, OUTPUT); // Red light
   pinMode(12, OUTPUT); // Yellow light
   pinMode(13, OUTPUT); // Green light
}

void loop() {
   digitalWrite(11, HIGH);   // RED on 
   digitalWrite(12, LOW);    // YELLOW off
   digitalWrite(13, LOW);    // GREEN off 
   delay(8000);
   
   digitalWrite(11, HIGH);   // RED on 
   digitalWrite(12, HIGH);   // YELLOW on
   digitalWrite(13, LOW);    // GREEN off 
   delay(1500);
   
   digitalWrite(11, LOW);   // RED off 
   digitalWrite(12, LOW);   // YELLOW off
   digitalWrite(13, HIGH);    // GREEN on 
   delay(5000);
   
   digitalWrite(11, LOW);   // RED off
   digitalWrite(12, HIGH);   // YELLOW on
   digitalWrite(13, LOW);    // GREEN off 
   delay(1500);
}

Advanced

void setup()   {
   pinMode(11, OUTPUT); // Red light
   pinMode(12, OUTPUT); // Yellow light
   pinMode(13, OUTPUT); // Green light
   
   pinMode(2, OUTPUT); // Red light
   pinMode(3, OUTPUT); // Green light
}

void loop() {
   digitalWrite(11, HIGH);   // RED on 
   digitalWrite(12, LOW);    // YELLOW off
   digitalWrite(13, LOW);    // GREEN off 
   digitalWrite(2, LOW);   // RED off 
   digitalWrite(3, HIGH);    // GREEN on
   delay(8000);
   
   digitalWrite(11, HIGH);   // RED on 
   digitalWrite(12, HIGH);   // YELLOW on
   digitalWrite(13, LOW);    // GREEN off 
   digitalWrite(2, LOW);   // RED off 
   digitalWrite(3, HIGH);    // GREEN on
   delay(1500);
   
   digitalWrite(11, LOW);   // RED off 
   digitalWrite(12, LOW);   // YELLOW off
   digitalWrite(13, HIGH);    // GREEN on 
   digitalWrite(2, HIGH);   // RED on 
   digitalWrite(3, LOW);    // GREEN off 
   delay(5000);
   
   digitalWrite(11, LOW);   // RED off
   digitalWrite(12, HIGH);   // YELLOW on
   digitalWrite(13, LOW);    // GREEN off 
   digitalWrite(2, HIGH);   // RED on 
   digitalWrite(3, LOW);    // GREEN off 
   delay(1500);
}