
A train without a marker on the rear, is a cut of cars...it's not a train until it gets a marker on the rear.
You won't see locomotives coupled to a TOFC train because the cars can't take the force against the rest of the train..
Stacks are a different matter. They can take the lateral force of a pusher in curves.
Auto-racks & TOFC cars require a certain number of regular cars between them & a pusher or mid-train slave...then it becomes a mixed-manifest freight.
Red flags you see around construction sites & on the rear of wide-loads on the highway with tapered ends on the handle(flagstaff) are designed to be placed on the hole through the knuckle on a coupler are a type of marker for locals, but FRA rules say that some way of measuring air pressure at the end of train is required.
Flashing rear-end devices(EOT for end-of-train) transmit air pressure & the signal is used to measure distance from the lead locomotive using a radio frequencies assigned to the railroads.
F.R.E.D. is a name that was originally used for EOT's but the inventor copyrighted the name so railroads quickly removed any reference to the name.
Some roads require a manned pusher to be reversed against the train, some do not, BNSF has been known to change their rules.
I used to run cabooses with every model train however in Trainz I found that switching is much easier without a cab.