4. One who is riding is like one who is walking – just as we stand up for a scholar who is walking, similarly, we stand up for a scholar who is riding.
Q1: Is this rule: *Rokhev kim’halekh dami*- (one who is riding is considered as if he was walking) – a universal principle in Halakha or is it local to honor/deference?
YE: It is only found in our context, although the Gemara (BT Kiddushin 33b) supports the principle with a law of ritual impurity (see there) – so it seems to be a general Halakhic principle as follows: If you are riding on an animal (in a car? on a bicycle?) then the status of your movement is predicated by the animal (you are moving) – not by you (you are stationary).
Q2: If it is universal, what are some other applications? If local, why is it applied here?
YE: In our case, the scholar is moving – and we disregard the fact that it is his animal, rather than his legs, that is moving him. In any case, the “personified Torah” (see above) is entering your personal space and you must show that honor.
Q3: In any case, what is the reasoning behind the rule?
YE: See above.
Rambam, Copyright (c) 1999 Project Genesis, Inc.