hc-sr04 distance sensor code issue

Hi, this is my first forum post and I an intermediate beginner to arduino.
I am also working on my first large, wheeled robot.
My goal for this robot is to have three hc-sr04 ultrasonic sensors, via if statements, control its path.
Due to the fact that I plan to use an lcd monitor as well as many other independant sensors and outputs, I will eventually use up all the pins on my arduino.
Therefore, in an effort to save pins, I found some code online in which you could hack the sensor to consume only one pin rather than two, aside from power and ground.

here is the code:

// ---------------------------------------------------------------------------
// Example NewPing library sketch that does a ping about 20 times per second.
// ---------------------------------------------------------------------------
#define ledPin 2
#include <NewPing.h>

#define TRIGGER_PIN 12 // Arduino pin tied to trigger pin on the ultrasonic sensor.
#define ECHO_PIN 12 // Arduino pin tied to echo pin on the ultrasonic sensor.
#define MAX_DISTANCE 200 // Maximum distance we want to ping for (in centimeters). Maximum sensor distance is rated at 400-500cm.

NewPing sonar(TRIGGER_PIN, ECHO_PIN, MAX_DISTANCE); // NewPing setup of pins and maximum distance.

void setup() {
pinMode (ledPin, OUTPUT);
Serial.begin(115200); // Open serial monitor at 115200 baud to see ping results.
}

void loop() {
delay(50); // Wait 50ms between pings (about 20 pings/sec). 29ms should be the shortest delay between pings.
unsigned int uS = sonar.ping(); // Send ping, get ping time in microseconds (uS).
Serial.print("Ping: ");
Serial.print(uS / US_ROUNDTRIP_CM); // Convert ping time to distance in cm and print result (0 = outside set distance range)
Serial.println(“cm”);

if (uS / US_ROUNDTRIP_CM > 20) { // This is where the LED On/Off happens
digitalWrite(ledPin,LOW); // When the Red condition is met, the Green LED should turn off

}
else {
digitalWrite(ledPin,HIGH);

}
if (uS / US_ROUNDTRIP_CM <= 20 || uS / US_ROUNDTRIP_CM >= 0){

}
else {
Serial.print(uS / US_ROUNDTRIP_CM);
Serial.println(" cm");
}
delay(500);
}

As you can see, rather than using something like “sensor1” in the if statements, you use
“uS / US_ROUNDTRIP_CM”.

My question is, what if I am using more than one sensor?
How am I to distinguish between the three sensors?
Any input about using something in the code or modification of the newping library to fit this would be greatly appreciated.

Thanks.