It's really up to you! But since you asked, we would recommend you put your TransitScreen where it will be most useful: where transportation decisions are made. This means somewhere with abundant foot traffic — a main lobby or near the elevators, for example — with standing space available.
As far as the size requirements of the display, we would recommend at least a 42" screen in order to ensure maximum readability. This should be mounted 6 feet off the floor at eye level.