Slack Action

Slack action
Sometimes violent movement of cars in a train relative to each other because of the "give" in each coupler.
Slip switch ...

Slack Action
The motion, forward or back, that one or more cars, locomotives, or parts of a train has without moving other coupled cars, locomotives, or parts of the train. Loose slack is the free movement or lost motion between parts of a train.

Scrap Iron Broken knuckle due to uncontrolled slack action in train or overly aggressive starting technique. Schedule That part of a timetable which prescribes class, direction, number and movement for a regular train.

Slack action (UK/US): Looseness in a train caused by mating clearances in couplers.[50]
Sleeper (UK), tie (US): Bars placed at 90° to the rail tracks to support the rails.

The make up of the train, the placement of loads and empties throughout, will dictate much of what happens with the slack action within as the train begins to come to a stop.

Articulation also eliminated slack action by having the front part of one car and the rear of the preceding one rest upon the same truck, held together by a sleeve joint, allowing it to round curves efficiently, yet unifying the whole train.

train in which one to four locomotives are placed at various points along the train. The locomotive engineer in the lead locomotive controls the distributed locomotives. DP'd trains are longer but have improved brake control and reduced slack action.

Slack Action Movement of part of a coupled train at a different speed than another part of the same train.

See also: Engine, Locomotive, Train, Slack, Yard