// GPIO pins for each traffic signal light (red, yellow, green)
int signal1[] = {5,35,19};
int signal2[] = {26,25,33};
int signal3[] = {32, 34, 18};
int signal4[] = {15, 1, 21};
 
 
// Ultrasonic sensor pins
int triggerpin1 = 13;
int echopin1 = 12;
int triggerpin2 = 27;
int echopin2 = 14;
int triggerpin3 = 22;
int echopin3 = 23;
int triggerpin4 = 2;
int echopin4 = 4;
 
long duration; // Time for ultrasonic signal to return
int S1, S2, S3, S4; // Distance measurements from each sensor
 
int t = 5; // Threshold distance to check for traffic presence
 
 
void setup()
{
 
  // Initialize traffic signal LEDs as outputs
  for (int i = 0; i < 3; i++)
  {
    pinMode(signal1[i], OUTPUT);
    pinMode(signal2[i], OUTPUT);
    pinMode(signal3[i], OUTPUT);
    pinMode(signal4[i], OUTPUT);
  }
 
  // Initialize ultrasonic sensor pins
  pinMode(triggerpin1, OUTPUT);
  pinMode(echopin1, INPUT);
  pinMode(triggerpin2, OUTPUT);
  pinMode(echopin2, INPUT);
  pinMode(triggerpin3, OUTPUT);
  pinMode(echopin3, INPUT);
  pinMode(triggerpin4, OUTPUT);
  pinMode(echopin4, INPUT);
}
 
 
void loop()
{

 
  // Measure distance from each ultrasonic sensor
  S1 = readDistance(triggerpin1, echopin1);
  S2 = readDistance(triggerpin2, echopin2);
  S3 = readDistance(triggerpin3, echopin3);
  S4 = readDistance(triggerpin4, echopin4);


 if(S1<t){
  digitalWrite(signal1[1], HIGH);
  delay(500);
  digitalWrite(signal1[1], LOW);
  while (S1 < t) {
   digitalWrite(signal1[2], HIGH);  
   digitalWrite(signal2[0], HIGH);
   digitalWrite(signal3[0], HIGH);
   digitalWrite(signal4[0], HIGH);      
   S1 = readDistance(triggerpin1, echopin1);
  }

  digitalWrite(signal1[2], LOW);  
  digitalWrite(signal2[0], LOW);
  digitalWrite(signal3[0], LOW);
  digitalWrite(signal4[0], LOW);      
 }
 else{
  signal1Function();
  }


  if(S2<t){
  digitalWrite(signal2[1], HIGH);
  delay(500);
  digitalWrite(signal2[1], LOW);
  while (S2 < t) {
   digitalWrite(signal1[0], HIGH);  
   digitalWrite(signal2[2], HIGH);
   digitalWrite(signal3[0], HIGH);
   digitalWrite(signal4[0], HIGH);      
   S2 = readDistance(triggerpin2, echopin2);
  }
 

  digitalWrite(signal1[0], LOW);  
  digitalWrite(signal2[2], LOW);
  digitalWrite(signal3[0], LOW);
  digitalWrite(signal4[0], LOW);      
 }
 else{
  signal2Function();  
 }


 if(S3<t){
  digitalWrite(signal3[1], HIGH);
  delay(500);
  digitalWrite(signal3[1], LOW);
  while (S3 < t) {
   digitalWrite(signal1[0], HIGH);  
   digitalWrite(signal2[0], HIGH);
   digitalWrite(signal3[2], HIGH);
   digitalWrite(signal4[0], HIGH);      
   S3 = readDistance(triggerpin3, echopin3);
  }
 
  digitalWrite(signal1[0], LOW);  
  digitalWrite(signal2[0], LOW);
  digitalWrite(signal3[2], LOW);
  digitalWrite(signal4[0], LOW);      
 }
 else{
  signal3Function();  
 }



 if(S4<t){
  digitalWrite(signal4[1], HIGH);
  delay(500);
  digitalWrite(signal4[1], LOW);
  while (S4 < t) {
   digitalWrite(signal1[0], HIGH);  
   digitalWrite(signal2[0], HIGH);
   digitalWrite(signal3[0], HIGH);
   digitalWrite(signal4[2], HIGH);      
   S4 = readDistance(triggerpin4, echopin4);
  }

  digitalWrite(signal1[0], LOW);  
  digitalWrite(signal2[0], LOW);
  digitalWrite(signal3[0], LOW);
  digitalWrite(signal4[2], LOW);      
 }
 else{
  signal4Function();
 }
  
}
 
 
int readDistance(int triggerPin, int echoPin)
{
  digitalWrite(triggerPin, LOW);
  delayMicroseconds(2);
  digitalWrite(triggerPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(triggerPin, LOW);
  duration = pulseIn(echoPin, HIGH);

  return duration * 0.034 / 2; // Convert to cm
}
 
 
// Define functions for handling each signal
void signal1Function()
{
  
  digitalWrite(signal2[0], HIGH);
  digitalWrite(signal3[0], HIGH);
  digitalWrite(signal4[0], HIGH);
  digitalWrite(signal1[1], HIGH);
  delay(500);
  digitalWrite(signal1[1], LOW);


  digitalWrite(signal1[2], HIGH);  


  delay(2000);



  digitalWrite(signal1[2], LOW);  
  digitalWrite(signal2[0], LOW);
  digitalWrite(signal3[0], LOW);
  digitalWrite(signal4[0], LOW);
}
void signal2Function()
{
  
  digitalWrite(signal1[0], HIGH);  
  digitalWrite(signal3[0], HIGH);
  digitalWrite(signal4[0], HIGH);
  digitalWrite(signal2[1], HIGH);
  delay(500);
  digitalWrite(signal2[1], LOW);
  digitalWrite(signal2[2], HIGH);
  delay(2000);
 
  digitalWrite(signal1[0], LOW);  
  digitalWrite(signal2[2], LOW);
  digitalWrite(signal3[0], LOW);
  digitalWrite(signal4[0], LOW);
}
void signal3Function()
{
  
  digitalWrite(signal1[0], HIGH);  
  digitalWrite(signal2[0], HIGH);
  digitalWrite(signal4[0], HIGH);
  digitalWrite(signal3[1], HIGH);
  delay(500);
  digitalWrite(signal3[1], LOW);
  digitalWrite(signal3[2], HIGH);
  delay(2000);

  digitalWrite(signal1[0], LOW);  
  digitalWrite(signal2[0], LOW);
  digitalWrite(signal3[2], LOW);
  digitalWrite(signal4[0], LOW);
}
void signal4Function()
{
  
  digitalWrite(signal1[0], HIGH);  
  digitalWrite(signal2[0], HIGH);
  digitalWrite(signal3[0], HIGH);
  digitalWrite(signal4[1], HIGH);
  delay(500);
  digitalWrite(signal4[1], LOW);
  digitalWrite(signal4[2], HIGH);
  delay(2000);

  digitalWrite(signal1[0], LOW);  
  digitalWrite(signal2[0], LOW);
  digitalWrite(signal3[0], LOW);
  digitalWrite(signal4[2], LOW);
}