const int trigPin1 = 2;
const int echoPin1 = 3;
const int trigPin2 = 4;
const int echoPin2 = 5;

const int greenLed1 = 6;
const int redLed1 = 7;
const int greenLed2 = 8;
const int redLed2 = 9;

void setup() {
  pinMode(trigPin1, OUTPUT);
  pinMode(echoPin1, INPUT);
  pinMode(trigPin2, OUTPUT);
  pinMode(echoPin2, INPUT);
  
  pinMode(greenLed1, OUTPUT);
  pinMode(redLed1, OUTPUT);
  pinMode(greenLed2, OUTPUT);
  pinMode(redLed2, OUTPUT);
  
  Serial.begin(9600);
}

void loop() {
  int distance1 = measureDistance(trigPin1, echoPin1);
  int distance2 = measureDistance(trigPin2, echoPin2);
  
  if (distance1 < 20) { // If car is detected within 20 cm
    digitalWrite(greenLed1, LOW);
    digitalWrite(redLed1, HIGH);
  } else {
    digitalWrite(greenLed1, HIGH);
    digitalWrite(redLed1, LOW);
  }

  if (distance2 < 20) { // If car is detected within 20 cm
    digitalWrite(greenLed2, LOW);
    digitalWrite(redLed2, HIGH);
  } else {
    digitalWrite(greenLed2, HIGH);
    digitalWrite(redLed2, LOW);
  }
  
  delay(500);
}

int measureDistance(int trigPin, int echoPin) {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  
  long duration = pulseIn(echoPin, HIGH);
  int distance = duration * 0.034 / 2; // Calculate distance in cm
  
  return distance;
}