Haven't you heard this again and again " The IQ of a group is equal to that of the least intelligent" . I guess it applies for the kids also. When you are in a social euphoria, rarely do you care about your surroundings or the interests of the being in the surroundings. Think about the noise and scenes we make when we meet a dear friend after a long while is a public place.
I am not presuming that a small noise from the car is goining to gain their attention for good, but rather it would be advisable to the driver that he better stop if doesnt want to make a genocide.In my opinion, the cell phone also will put you into such a social euphoria at times, and you will loose your sense or manners in the public. I have seen a guy kicking a post while talking on the phone. Who in their right sense will do that in public!
Perhaps, the right manners to teach kids would not be how to cross a road properly, but how not to embarass yourself while using a mobile phone, since mobile phones will be a part of our life for the forseable future...