Dividing train

A dividing train is a train that separates into two trains partway along its route, so as to serve two destinations.
Operation.
On the initial leg of its journey, the train is driven as normal by a single crew. At a designated station before a junction, the train stops and some of the cars are detached, with passengers or goods still on board. The front part of the train then departs to run the remainder of its route. A second train is then formed from the detached cars, the points are changed at the junction, and a new crew drives the train on a different route to a second destination. Where the train is formed of "multiple units" – self-contained trainsets with their own propulsion and driving cabs – two or more units work in multiple on the first leg. After detachment, the second crew drives in the trailing unit's front cab.
On the return journey, the two trains may join at the same station where they divided. Special signalling is required at the station, both to recognise the division of the outbound train as intentional, and to allow the two inbound trains to enter the same block. The British rail network uses a "draw ahead" signal for the latter.
Examples.
Japan.
There are several dividing train services in Japan, and each route has its own name.
United Kingdom.
Dividing trains operate on several lines on the British railway network, commonly (although not exclusively) in the south of the country. To ensure consistent journey times, the front part of a dividing train usually becomes the rear of the returning service when it reunites.
In addition, some services discard carriages part-way along the route, & pick them back up on the return journey. This may be because a portion of the line has short platforms at a number of its stations, or because of demand being much higher on one section than another.
Reception.
Dividing trains are sometimes seen as a pitfall for the unwary traveller.