Which position must the switch be secured to enable its main track use?

The main track of a railroad requires switches to be in a specific position to ensure safe and effective operation. When a switch is in the normal position, it is aligned to allow trains to continue on the main track without any hindrance or risk of derailment. This means that the points of the switch are set to connect the main line, ensuring that any train passing through will be directed safely onto that track.

The normal position is essential because it guarantees that the most common route for trains, which is the main track, is clear and adequately configured. This is critical for maintaining the flow of rail traffic and preventing accidents.

In contrast, other positions like the temporary, neutral, or shutdown positions are not intended for regular use on the main track. The temporary position may indicate that the switch is set for a specific event or scenario but does not ensure the usual main line function. Similarly, the neutral position might leave the switch in a state that doesn't lead onto either track, and the shutdown position generally places the track out of service entirely, which is not safe for main track operations. Thus, the normal position is the designated and safest configuration for utilizing the main track.