int trigPin = 8;
int echoPin = 7;
int LEDV = 9;
int LEDR = 6;
float Speed = 0.0343;
long duration, distance;

void setup()
{
   pinMode(trigPin, OUTPUT); 

   pinMode(echoPin, INPUT); 

   pinMode(LEDV, OUTPUT); 

   pinMode(LEDR, OUTPUT); 

   digitalWrite (LEDV , LOW); 

   digitalWrite (LEDR , LOW); 
}
void loop()
 {   
   digitalWrite(trigPin, LOW); 

   delayMicroseconds(2); 

   digitalWrite(trigPin, HIGH); 
   delayMicroseconds(10); 

   digitalWrite(trigPin, LOW); 

   duration = pulseIn(echoPin, HIGH) ; 

   distance = Speed* duration / 2; 
                                    

   if ( distance < 20){
       digitalWrite (LEDV , HIGH); 

       digitalWrite (LEDR , LOW);

   }
   else{ // otherwise
       digitalWrite (LEDV , LOW); 
       digitalWrite (LEDR , HIGH); 
 }
}