A motorman should use the route request button when the train is approaching a junction to communicate with the signaling center and request the correct routing for the train.
The route request button on trains is typically used when a train is approaching a junction. This button allows the motorman or train driver to communicate with the signal control center and request the necessary route through the junction where multiple tracks may diverge or converge.
It is not commonly used when approaching a station, tunnel, or bridge, as route selections in these circumstances are typically predefined and do not require the same level of intervention by the motorman. The button helps in managing the train's path efficiently to avoid confusion and accidents on the tracks where multiple route options are available.
In conclusion, the route request button is crucial for the safe and efficient operation of trains at junctions where decisions on the direction of the train need to be communicated to the signaling center.