Control Car
A control car, control trailer or driving trailer is a generic term for a non-powered railroad (US) or railway (UIC) vehicle that can control operation of a train from the end opposite to the position of the locomotive. They can be used with Diesel or electric motive power, allowing push-pull operation without the use of an additional locomotive. They can also be used with a power car or a railcar. In a few cases control cars were used with steam locomotives, especially in Germany and France.

In the United States, cab cars are control cars similar to regular passenger car, but with a full driver's compartment built into one or both ends. They can be very similar to regular rail cars, to the point of including a gangway between cars so that they could be used in the middle of a passenger train like a regular car if necessary. European railways have used such equipment since the 1920s. In the United States they appeared for the first time in the 1960s. In the United Kingdom, driving trailers may have one or two driving cabs.

Trains operating with a locomotive at one end and a control car at the other do not require the locomotive to run around to the opposite end of the train when reversing direction at a terminus. Control cars can carry passengers, baggage, mail or a combination thereof, and may, when used together with Diesel locomotives, contain an engine-generator set to provide head-end power (HEP).

In addition to the driver's cab, which has all the controls and gauges necessary for remotely operating the locomotive, control cars usually have a horn, whistle, bell, or plow (as appropriate), and all of the lights that would normally be on a locomotive. They must also be fitted with all necessary communication and safety systems like GSM-R or European Train Control System (ETCS).

Control method
The classic control method was a multiple unit cable with jumpers between cars. In North America and Ireland a standard AAR 27-wire cable is used, in other countries cables with up to 61 wires can be found. A more recent method is to control the train through a Time-Division Multiplexed (TDM) connection, which usually works with two (protected) wires.

North America
Some commuter rail agencies in the United States routinely use cab cars in place of regular passenger coaches on trains. However, with commuter agencies such as Metra, these cars make the train less aerodynamic. The Chicago and North Western Railway had 42 control cabs built by Pullman-Standard in 1960, which eliminated the need for its trains or locomotives to be turned around. It was an outgrowth of multiple-unit operation that was already common on diesel locomotives of the time. The Agence métropolitaine de transport in Canada uses control cars on all its trains, except its electric multiple units, which run as double- ended semipermanent coupled three-car rakes.

During the mid-1990s, as push-pull operations became more common in the United States, cab-cars came under criticism  for providing less protection to engine crews during level crossing accidents. This has been addressed by providing additional reinforcing in cab cars. This criticism became stronger after the 2005 Glendale train crash, in which a Metrolink train collided with a Jeep Grand Cherokee at a level crossing in California. The train was traveling with its cab car in the front, and the train jackknifed. Sadly, eleven people were killed in the accident, and about 180 were injured.

In early 2015, another collision occurred in Oxnard, California, involving one of Metrolink's improved "Rotem" cab cars at the front of the train hitting a truck at a crossing. The truck driver left his vehicle before the impact, but unfortunately the train jackknifed from the collision which resulted in multiple car derailments, injuries, and the death of the engineer.

Converted locomotives
From the 1970s until 1999, the Long Island Rail Road used a number of older locomotives converted to "power packs". The original prime movers were replaced with 600 horsepower (450 kW) engines/generators solely for supplying HEP with the engineer's control stand left intact. Locomotives converted included ALCO FA-1s and FA-2s, EMD F7s and one F9. Ontario's GO Transit had a similar program for EMD FP7s.

NPCU "Cabbage"

Amtrak developed their Non-powered Control Unit (NPCU) by removing the prime mover, main alternator, and traction motors from surplus F40 locomotives. The control stand was left in place, as were equipment allowing horn, bell and headlight operation. A floor and roll-up side-doors were then installed to allow for baggage service, leading to the nickname "cab-baggage cars" or "cabbages". The F40s rebuilt into NPCUs are identified by their former three-digit road number with the number 90 added, e.g., former locomotive No. 250 is now NPCU No. 90250.

Six NPCUs rebuilt for Cascades service in the Pacific Northwest (Nos. 90250-90253, No. 90230 and No. 90340) do not have the roll-up side doors, because the Talgo sets on which they operate have a baggage car as part of the trainset. Instead, they have a concrete weight for FRA safety reasons. Four NPCUs are used on the Amtrak Downeaster and are painted with the Downeaster logo on the side instead of the Amtrak logo.

One NPCU, Amtrak No. 406, is used to provide power for Amtrak's 40th Anniversary Exhibit Train. It retains its original number, unlike other NPCUs.

NPCU No. 90208 received a special veterans appreciation scheme in September 2015. NPCU No. 90221 received the same scheme in 2016.

See also:

F40PH

Downeaster

Cascades

A Northstar Line cab car (BiLevel Coach) in Elk River, Minnesota.

By Mulad - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11607915

NJ Transit Comet V Cab Car in Bay Head, New Jersey.
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NJ Transit Comet V Cab Car in Bay Head, New Jersey.

By James Zimenoff - Transferred from en.wikipedia to Commons by Sreejithk2000 using CommonsHelper., Attribution, https://commons.wikimedia.org/w/index.php?curid=16267372

A Northstar Line cab car in Elk River, Minnesota.

An Amtrak Downeaster NPCU "Cabbage" in Brunswick, Maine.

By Bubblecuffer - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=27445099

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