How may a track car with Form D authority to operate in both directions operate?

A track car that has been granted Form D authority for operation in both directions is specifically allowed to move in either direction along the track. This flexibility is essential for track cars, which may need to travel to various locations for maintenance or repairs and can require changing direction more frequently than standard trains.

The decision to allow operation in either direction under Form D is designed to enhance the efficiency of track maintenance activities and ensure that the workflow is uninterrupted. This means that as long as the train crew adheres to the guidelines provided in the Form D, they can choose the direction of their movement based on operational needs without requiring further authorization every time they need to switch direction.

The other choices reflect restrictions that are not applicable in this scenario. For example, limiting the track car to operate in one direction or preventing stops would contradict the operational flexibility intended with Form D authority. Additionally, while it's true that any additional movements may require Dispatcher authorization, the specific context of the question here is focused on the inherent ability to operate in both directions, which is already granted under the Form D itself without needing additional authorization for the direction of travel.