It’s not the brakes on the rear car, it’s doing an emergency brake of the entire train from the last car. It dumps the brake line that runs through the length of the train.
This is part of the train safety system, if the brake line is broken, if cars pull apart, then the brakes on all cars are activated.
Doing this from the rear of the train is less desirable than from the front, as it could possibly pull the train apart as braking travels up the length of the train.
This used to be one of the reasons for having a caboose on the end, with people in it. They could activate the emergency brakes if for some reason it didn’t work from the front.
This is part of the train safety system, if the brake line is broken, if cars pull apart, then the brakes on all cars are activated.
Doing this from the rear of the train is less desirable than from the front, as it could possibly pull the train apart as braking travels up the length of the train.
This used to be one of the reasons for having a caboose on the end, with people in it. They could activate the emergency brakes if for some reason it didn’t work from the front.