Why AMBULANCE is Written Backwards ?

We find that Board "AMBULANCE" is written reverse on the Ambulance vehicle. Why ??

Word AMBULANCE is written reverse as because the mirror shows a property of what we call in scientific terms is "lateral inversion"!
It is a phenomenon in which when an object is placed in front of the mirror the right side of the object becomes left side of the image and the left side of the object becomes right side of the image...therefore the already written inverse AMBULANCE when viewed through the rear view mirror(having convex mirror which provides a wide view of field) of the vehicle then the driver could easily get to know about the ambulance and give way to it.

The siren also helps the other vehicle that are few distance apart to know about the ambulance is on the way behind it and even they can further make way for the ambulance!