int R1 = 2, Y1 = 3, G1 = 4;
int R2 = 5, Y2 = 6, G2 = 7;
int trig1 = 8, echo1 = 9;
int trig2 = 10, echo2 = 11;
long duration;
int distance1, distance2;

void setup() {
  pinMode(R1, OUTPUT); pinMode(Y1, OUTPUT); pinMode(G1, OUTPUT);
  pinMode(R2, OUTPUT); pinMode(Y2, OUTPUT); pinMode(G2, OUTPUT);
  pinMode(trig1, OUTPUT); pinMode(echo1, INPUT);
  pinMode(trig2, OUTPUT); pinMode(echo2, INPUT);
  Serial.begin(9600);
}

int getDistance(int trig, int echo) {
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);
  duration = pulseIn(echo, HIGH);
  return duration * 0.034 / 2;
}

void loop() {
  distance1 = getDistance(trig1, echo1);
  distance2 = getDistance(trig2, echo2);

  if (distance1 < 15 && distance2 >= 15) {
    digitalWrite(G1, HIGH); digitalWrite(R2, HIGH);
    delay(5000);
    digitalWrite(G1, LOW); digitalWrite(Y1, HIGH);
    delay(2000);
    digitalWrite(Y1, LOW); digitalWrite(R2, LOW);
  } 
  else if (distance2 < 15 && distance1 >= 15) {
    digitalWrite(G2, HIGH); digitalWrite(R1, HIGH);
    delay(5000);
    digitalWrite(G2, LOW); digitalWrite(Y2, HIGH);
    delay(2000);
    digitalWrite(Y2, LOW); digitalWrite(R1, LOW);
  } 
  else {
    digitalWrite(G1, HIGH); digitalWrite(R2, HIGH);
    delay(4000);
    digitalWrite(G1, LOW); digitalWrite(Y1, HIGH);
    delay(2000);
    digitalWrite(Y1, LOW); digitalWrite(R2, LOW);

    digitalWrite(G2, HIGH); digitalWrite(R1, HIGH);
    delay(4000);
    digitalWrite(G2, LOW); digitalWrite(Y2, HIGH);
    delay(2000);
    digitalWrite(Y2, LOW); digitalWrite(R1, LOW);
  }
}