When a Public Utility Vehicle is not in motion, is there a necessity for a person who wants to ride the same to signal his intention to board?

No. When the bus is not in motion there is no necessity for a person who wants to ride the same to signal his intention to board. A public utility bus, once it stops, is in effect making a continuous offer to bus riders. Hence, it becomes the duty of the driver and the conductor, every time the bus stops, to do no act that would have the effect of increasing the peril to a passenger while he was attempting to board the same. The premature acceleration of the bus in this case was a breach of such duty. (Dangwa vs. CA, G.R. No. 95582, October 7, 1991)