Ahhh moving the goal posts I see... from someone "telling me" to "there is a sign placed on bonnet".
To answer your original claim, I have never had someone physically come up to me and tell me to not smoke/turn off vehicle/do not use mobile phone.
FWIW, they place no signs on the bonnet of my vehicles, they scratch the paint and pump chump is told not to place them on the bonnet.