int led1 = 12;
int led2 = 11;
int led3 = 10;
void setup() {
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(led1, HIGH);
  Serial.println("RED LIGHT, PLEASE STOP.");
  delay(15000);
  digitalWrite(led1, LOW);
  digitalWrite(led2, HIGH);
  Serial.println("YELLOW LIGHT, PLEASE WAIT.");
  delay(15000);
  digitalWrite(led2, LOW);
  digitalWrite(led3, HIGH);
  Serial.println("GREEN LIGHT, YOU CAN GO NOW.");
  delay(15000);
  digitalWrite(led3, LOW);
}