What does a lighted operator's indication signal to the operator?

The lighted operator's indication is crucial for ensuring safety and efficiency during train operations. When the indication signals that the side doors are closed and locked, it confirms that the train is secure and ready for movement. This is important for the safety of passengers, as open doors could pose a risk during travel.

When the operator sees this lighted indication, they can be confident that no passengers are at risk of falling or exiting the train unexpectedly while it is in motion. This assurance facilitates smooth operations, aligning with safety protocols that require doors to be secured before departure.

Other options represent different stages or conditions of train operation but do not specifically address the critical safety aspect of ensuring the doors are properly secured before the train departs.