Traffic light

// defines pins numbers
const int trigPin = 9;
const int echoPin = 8;
const int led1 = 12;
const int led2 = 11;
const int led3 =6;
const int led4 =5;
const int led5 =2;
const int led6 = 3;
// defines variables
long duration;
int distance;
int safetyDistance;
void setup() {
pinMode(trigPin, OUTPUT); // Sets the trigPin as an Output
pinMode(echoPin, INPUT); // Sets the echoPin as an Input
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);
pinMode(led3, OUTPUT);
pinMode(led4, OUTPUT);
pinMode(led5, OUTPUT);
pinMode(led6, OUTPUT);
Serial.begin(9600); // Starts the serial communication
}
void loop() {
// Clears the trigPin
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
// Sets the trigPin on HIGH state for 10 micro seconds
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
// Reads the echoPin, returns the sound wave travel time in microseconds
duration = pulseIn(echoPin, HIGH);
// Calculating the distance
distance= duration*0.034/2;
safetyDistance = distance;
if (safetyDistance>20 && safetyDistance<35)
{
 digitalWrite(led1,HIGH);
 digitalWrite(led2,HIGH);
 digitalWrite(led3, LOW);
 digitalWrite(led4, LOW);
 digitalWrite(led5, LOW);
 digitalWrite(led6, LOW);
}
else if(safetyDistance>17 && safetyDistance<25)
{
 digitalWrite(led1, LOW);
 digitalWrite(led2, LOW);
 digitalWrite(led3, HIGH);
 digitalWrite(led4, HIGH);
 digitalWrite(led5, LOW);
 digitalWrite(led6, LOW);
}
else if(safetyDistance<=10)
{
 digitalWrite(led1, LOW);
 digitalWrite(led2, LOW);
 digitalWrite(led3, LOW);
 digitalWrite(led4, LOW);
 digitalWrite(led5, HIGH);
 digitalWrite(led6, HIGH);
}
else
{
 digitalWrite(led1, LOW);
 digitalWrite(led2, LOW);
 digitalWrite(led3, LOW);
 digitalWrite(led4, LOW);
 digitalWrite(led5, LOW);
 digitalWrite(led6, LOW);
}
// Prints the distance on the Serial Monitor
Serial.print("Distance: ");
Serial.println(distance);
}