Why is the word 'ambulance' written in a reverse form in front of an ambulance?

When an object is placed in front of a plane mirror, then the right side of object appears to become the left side of image; and the left side of object appears to become the right side of image. This change of sides of an object and its mirror image is called lateral inversion. The word AMBULANCE on the hospital vans is written in the form of its mirror image as because any vehicle driver which is ahead of ambulance van can see the laterally inverted alphabets correctly from his rear-view mirror which is convex mirror. Thus, he can make way for it to pass through and enable it to reach the hospital quickly.