Request stop
In public transport, a request stop, flag stop, or whistle stop describes a stop or station at which trains or buses stop only on request; that is, only if there are passengers to be picked up or dropped off. In this way, ill-frequented stops can be incorporated into a route without introducing unnecessary delay.
Vehicles may also save fuel by continuing through a station when there is no need to stop.
There may not always be a significant savings on time if there is no one to pick up because vehicles going past a request stop may need to slow down enough to be able to stop if there are passengers waiting. Request stops may also introduce extra travel time variability and increase the need for schedule padding.
Implementations
The methods by which transit vehicles are notified that there are passengers waiting to be picked up at a request stop vary by transit system and by route.
Local transport
Most local, inner-city bus operations operate almost all of their stops as request stops, even if there is almost always a passenger boarding or alighting. To distinguish stops that are served on every trip, these are usually called stations and they are most often at the terminals of a route. Such stops are often also used as timepoints.