I think the 'official' (per rulebook) definition of "train" was "one or more locomotives, coupled, carrying markers". Since (apparently no one uses markers anymore, has the definition changed?
Remember: In South Carolina, North is southeast of Due West... HIOAg /Bill
From the General Code of Operating Rules.
"Train
One or more engines coupled, with or without cars, displaying a marker, and authorized to operate on a main track.
A term that when used in connection with speed restrictions, flag protection, and the observance of all signals and signal rules also applies to engines."
No one uses markers anymore? News to me, and just about every other railroader.
"5.10 Markers
A marker of the prescribed type must be displayed on the trailing end of the rear car to indicate the rear of the train.
5.10.1 Highly Visible Markers Display a highly visible marker at the rear of every train as follows: • From 1 hour before sunset to 1 hour after sunrise. • When weather conditions restrict visibility to less than 1/2 mile.Highly Visible Marker
A marker equipped with a functioning photoelectric cell will automatically illuminate at the appropriate time. When an engine is operating without cars or is at the rear of the train, the trailing headlight illuminated on dim may be used as a marker.
Inspection of Marker
When a highly visible marker is required, a qualified employee must inspect it at the initial terminal and at each crew change point. To determine if the marker is functioning properly, the employee will inspect it by observation or by telemetry display in the cab of the engine. The engineer must be informed of the results of the inspection.5.10.2 Alternative Markers
Display a reflector, red flag, or light fixture at the rear of the train as the marker when any of the following conditions exists:
A highly visible marker is not required.
• A defective car must be placed at the rear for movement to a repair point.
• The rear portion of the train is disabled and cannot be moved, and a highly visible marker cannot be displayed on the rear of the portion to be moved. or
• The highly visible marker becomes inoperative enroute. If this occurs, notify the train dispatcher and move the train to the next forward location where the highly visible marker can be repaired or replaced."
Trains still have markers, they're just not the type of lights or lamps that used to hang on cabooses.
Jeff
A series of parts or elements that together constitute a system for producing a result and especially for carrying on a process (as of manufacture) automatically
This is Transport Canada's definition:
"An engine with or without cars intended to operate on the main track at speeds in excess of 15 MPH or a track unit when so designated."