This is the enemy. This is FRED. This blinking black box replaced the caboose on the rear end of the vast majority of freight trains in North America.
FRED is an acronym of Flashing Rear End Device. It is also known as End Of Train Device or EOT for short. The simplest FREDs are nothing more than a box holding a blinking light and a battey.
More advanced FREDs monitor main brake line pressure and relay that data back to the engineer in the lead locomotive's cab. Some FREDs can remotely apply the brakes using a signal from the engineer in the lead loco. Though that can be complicated and defeated by ice in the line.
Most railfans hate this little box. So do I.