In rail transport, a request stop, flag stop or whistle stop describes a station at which trains stop only on an as-needed basis, that is, only if there are passengers to be picked up or dropped off. At request stops for which there are no passengers to be dropped off, trains need only slow in the vicinity of the platform — or, in some cases, pass it at speed — instead of coming to a complete stop at an empty platform. In this way, lightly used stations can remain open and be served efficiently, rather than be closed