Bye bye FRED.
 
CPKC distributed power trailing units no longer need a FRED (Flashing Rear End Device), or the more properly named Sense and Braking Unit (SBU).
 
In lieu of these, a large red dot appears on the rear of appropriate units, while the rear headlight is switched on and dimmed.
 
According to Wikipedia, the earliest known method showing the position, and completeness of a train, was by the Stockton & Darlington Railway in the 1830s.
 
This early reference refers to the use of a burning brazier on the rear of a locomotive.
 
It's easy to imagine that the danger represented by this was as significant as the risks it was trying to counter.
 
This evolved into the use of a red tail lamp so signallers working under the absolute block system could ensure that trains were complete when passing their signal box.