What is the primary function of an end of Train Device on the rear car of a train?

The primary function of an end of train device is to monitor brake pipe pressure. This device plays a crucial role in ensuring the safety and operational integrity of freight trains. By continuously measuring the pressure in the brake line at the rear of the train, it provides real-time information about the effectiveness of the train's braking system. If there is a drop in pressure, it indicates that there may be an issue with the brakes, and this information can be relayed to the locomotive engineer, allowing for prompt action to be taken to prevent accidents.

In addition, the end of train device often includes other features, like a flashing light or reflector, to signal the end of the train to other rail operators and ensure safety on the tracks. However, its primary focus remains on monitoring the brake pipe pressure, which is critical for maintaining safe operations.