What speed must an extra train operate after receiving permission to enter the main track?

When an extra train receives permission to enter the main track, it must operate at restricted speed. This is essential to ensure the safety of train operations, especially when the circumstances might include uncertain track conditions or the presence of other trains on the same track.

Restricted speed allows the train to stop within half of the range of vision ahead, which is critical in maintaining safety when there may be signals, work zones, or other factors that require the train to be able to react quickly.

Normal speed, while applicable under other circumstances, is not advisable in this situation due to the potential for unforeseen obstacles or hazards. Operating as fast as possible would be reckless, and limiting the speed to just two miles per hour is impractical and unnecessary beyond specific low-speed operations. Overall, adhering to the requirement of operating at restricted speed provides a necessary buffer for the safety of the crew and the train.