You might have witnessed an Ambulance with backward spelling written on it.

This backward spelling is always on the front side of the Ambulance.

You might've also seen that cars and bikes have sides & rare mirrors are convection mirrors.

And when the Ambulance is optical in the mirror, it will be posterior.

It is the cause that Ambulance spelling is written backwards.

The spelling is written in green or blue colour.

These colours can be far-sighted because of their wavelength.