Rail yard

In the case of all classification or sorting yards, human intelligence plays a primary role in setting a strategy for the 'switching operations'; the fewer times coupling operations need to be made and the less distance traveled, the faster the operation, the better the strategy and the sooner the newly configured consist can be joined to its outbound train.  

• Switching yards, staging yards or Shunting yards are typically graded to be flat yards, where switch engines manually shuffle and maneuver cars from: a) train arrival tracks, to a b) consist breakdown track, c) to an consist assembly track, thence to d) departure tracks of the yard.
  • A large sub-group of such yards are known as Staging yards, which are yards serving an end destination that is also a collection yard starting car groups for departure. These seemingly incompatible tasks are because the operating or road company and its locomotive drops off empties and picks up full cars waiting departure which have been spotted and assembled by local switch engines. The long haul carrier makes the round trip with a minimal turn around time, and the local switch engine transfers empties to the loading yard when the industries output is ready to be shipped.
  • This activity is duplicated in a Transfer yard, the difference being in the latter many or several businesses and industries are serviced by the local switcher, which is part of the yard equipment, and the industry pays a cargo transfer fee to the railroad or yard operating company. In the staging yard, the locomotive is most likely operated by industry (refinery, chemical company or coal mine personnel); and ownership of the yard in both cases is a matter of business, and could be any imaginable combination. Ownership and operation are quite often a matter of leases and interests[2]
• Hump yard and gravity yard tracks are usually highly automated and designed for the efficient break-down, sorting, and recombining of freight into consists, so they are equipped with mechanical retarders (external brakes) and scales that a computer or operator uses along with knowledge of the gradient of the hump to calculate and control the speed of the cars as they roll downhill to their destination tracks. These modern sorting and classification systems are sophisticated enough to allow a first car to roll to a stop near the end of its classification track, and, by slowing the speed of subsequent cars down the hump, shorten the distance for the following series of cars so they can bump and couple gently, without damaging one another. Since overall throughput speed matters, many have small pneumatic, hydraulic or spring-driven braking retarders (below, right) to adjust and slow speed both before and after yard switch points. Along with car tracking and load tracking to destination technologies such as RFID, long trains can be broken down and reconfigured in transfer yards or operations in remarkable time.

A hump classification type of yard. The photographer is positioned near where cars are decoupled and begin to accelerate downhill past a scale. The speed regulation (retarder brakes and speed sensors) devices shown in the foreground adjust the car speed for the calculated soft-coupling on arrival along the sorting track for the consist it is being routed to join.

Smaller local hydraulic "Dowty retarders" finesse the speed of a car being sorted as it approaches a switch or the new consists to which it is being joined.