What must the lead locomotive be equipped with on train movements requiring dynamic brakes?

The lead locomotive must be equipped with an operative accelerometer for train movements requiring dynamic brakes. An accelerometer is essential because it provides real-time measurements of the locomotive's acceleration, which is critical for effectively managing the dynamic braking system. By determining how quickly or slowly the train is decelerating, the crew can make informed decisions about braking intensity and ensure safe train operations.

Dynamic braking relies on the electrical resistance generated by the traction motors as they are used in reverse to slow the train, and the accelerometer aids in monitoring the effectiveness of this braking method. Accurate feedback from the accelerometer ensures that the train does not exceed safe speed limits while decelerating, which is vital for both safety and operational efficiency during train movements.

The other options do not provide the necessary functionality for dynamic braking. A backup battery system, while useful for emergency power, does not aid in the braking process itself. A secondary throttle is not required specifically for dynamic brakes and serves a different purpose related to power control. Additional passenger cars do not play a role in the braking mechanism of the lead locomotive.