Final answer:
In the event of lost communication between a motorman and flagman, the motorman should halt the train and remain stationary until proper communication is restored to ensure safety.
Step-by-step explanation:
When there is a loss of positive communication between the motorman and the flagman while the train is in motion, the motorman should stop moving and become stationary till it passes by. This is the safest course of action to prevent any potential accidents or misunderstandings that could arise due to the lack of communication. It is imperative to prioritize safety and ensure that clear signals are established before the train is set in motion again.
When there is a loss of positive communication between the motorman and the flagman while the train is in motion, the motorman should stop moving and become stationary until it passes by.
This is important to ensure safety and prevent accidents or collisions.
Running toward or alongside the ambulance (options b and c) would be dangerous and irresponsible, as it may put the motorman's life at risk and hinder the operation of the train.