Final answer:
The distance required to stop with a lowered crossing gate, flashing electric signal, or rapidly-approaching train is 30 feet.
Step-by-step explanation:
To ensure safety when approaching a lowered crossing gate, a flashing electric signal, or a rapidly-approaching train, you must always stop within 30 feet. This distance allows the driver enough time to react and bring the vehicle to a complete stop without colliding with the crossing gate, signal, or train. It is important to adhere to this rule to prevent accidents and ensure the safety of everyone involved.