Smart Road

int const trigPin = 10;
int const echoPin = 9;
int const ledPin = 2;
int const Red = 12;
int const Yellow =11;
int const Green =13;
int const buzzerPin=4;
void setup()
{
digitalWrite(Green,LOW);
pinMode(trigPin, OUTPUT); 
pinMode(echoPin, INPUT); 
pinMode(ledpin, OUTPUT); 
pinMode(11,OUTPUT);
pinMode(12,OUTPUT);
pinMode(13,OUTPUT);
pinMode(4,OUTPUT);
}
void loop()
{
  digitalWrite(Red,HIGH);
delay(2000);

digitalWrite(Red,LOW);
digitalWrite(Yellow,HIGH);
delay(2000);
digitalWrite(Yellow,LOW);
digitalWrite(Green,HIGH);
delay(2000);
digitalWrite(Green,LOW);
int duration, distance;

digitalWrite(trigPin, HIGH);
delay(1);
digitalWrite(trigPin, LOW);
duration = pulseIn(echoPin, HIGH);
distance = (duration/2) / 29.1;
if (distance <= 5 && distance >= 0) {

digitalWrite(ledpin, HIGH);
} 
else if(distance<=1)
{
  digitalWrite(ledpin, HIGH);
  digitalWrite(buzzpin, HIGH);
  
  }
else {
digitalWrite(ledpin, LOW);
}
Serial.print(distance);
delay(60);
}