RAUNAK SUHAG

// Automatic Traffic Light — Arduino UNO
// HC-SR04 measures distance → density score → green time

const int trigPins[] = {2, 4, 6, 8};
const int echoPins[] = {3, 5, 7, 9};
const int redPins[]  = {22,26,30,34};
const int yelPins[]  = {23,27,31,35};
const int grnPins[]  = {24,28,32,36};

long getDistance(int lane) {
  digitalWrite(trigPins[lane], HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPins[lane], LOW);
  long d = pulseIn(echoPins[lane], HIGH);
  return d * 0.034 / 2; // cm
}

int getDensity(long dist) {
  return map(dist, 5, 150, 5, 0); // closer = denser
}

void setLight(int lane, char color) {
  digitalWrite(redPins[lane], color == 'R');
  digitalWrite(yelPins[lane], color == 'Y');
  digitalWrite(grnPins[lane], color == 'G');
}

void loop() {
  int density[4];
  for (int i=0; i<4; i++)
    density[i] = getDensity(getDistance(i));

  // Sort lanes by density (highest first)
  int order[] = {0,1,2,3};
  for(int i=0;i<3;i++)
    for(int j=i+1;j<4;j++)
      if(density[order[j]] > density[order[i]])
        { int t=order[i]; order[i]=order[j]; order[j]=t; }

  for (int i=0; i<4; i++) {
    int L = order[i];
    int greenMs = map(density[L], 0,5, 3000,8000);
    // All RED, then active lane goes GREEN
    for(int j=0;j<4;j++) setLight(j,'R');
    setLight(L, 'G');  delay(greenMs);
    setLight(L, 'Y');  delay(1500);
    setLight(L, 'R');  delay(300);
  }
}

Drag sliders to change vehicle density — system auto-cycles lanes by priority

// BT Controlled Car — Arduino UNO + HC-06 + L298N

#include <SoftwareSerial.h>
SoftwareSerial BT(10, 11); // RX, TX

// L298N Motor A (Left)
const int IN1=2, IN2=3, ENA=5;
// L298N Motor B (Right)
const int IN3=4, IN4=7, ENB=6;

void setup() {
  BT.begin(9600);
  pinMode(IN1,OUTPUT); pinMode(IN2,OUTPUT);
  pinMode(IN3,OUTPUT); pinMode(IN4,OUTPUT);
  analogWrite(ENA, 200); analogWrite(ENB, 200);
}

void moveForward()  { digitalWrite(IN1,HIGH); digitalWrite(IN2,LOW);
                       digitalWrite(IN3,HIGH); digitalWrite(IN4,LOW); }
void moveBackward() { digitalWrite(IN1,LOW);  digitalWrite(IN2,HIGH);
                       digitalWrite(IN3,LOW);  digitalWrite(IN4,HIGH); }
void turnLeft()     { digitalWrite(IN1,LOW);  digitalWrite(IN2,HIGH);
                       digitalWrite(IN3,HIGH); digitalWrite(IN4,LOW); }
void turnRight()    { digitalWrite(IN1,HIGH); digitalWrite(IN2,LOW);
                       digitalWrite(IN3,LOW);  digitalWrite(IN4,HIGH); }
void stopCar()      { digitalWrite(IN1,LOW);  digitalWrite(IN2,LOW);
                       digitalWrite(IN3,LOW);  digitalWrite(IN4,LOW); }

void loop() {
  if (BT.available()) {
    char cmd = BT.read();
    switch(cmd) {
      case 'F': moveForward();  break;
      case 'B': moveBackward(); break;
      case 'L': turnLeft();     break;
      case 'R': turnRight();    break;
      case 'S': stopCar();      break;
    }
  }
}

Use buttons or ← ↑ ↓ → arrow keys to drive