How fast can freight trains move under Rule 556 when cab signals fail?

Under Rule 556, when cab signals fail, freight trains are restricted to a maximum speed of 49 mph. This rule is critical for maintaining safety by ensuring trains do not operate at excessive speeds in the event of signal failures. The limitation aims to provide a buffer for train crews to respond appropriately to any unforeseen conditions or obstacles on the track.

The establishment of this specific speed limit is based on safety protocols that account for the reduced ability to receive real-time signal updates, which affects the train's operation. Train crews are trained to adhere to these rules to prevent accidents and ensure safe transportation of freight.

Conversely, higher speeds would increase the risk of derailments or collisions, especially when operating without proper signal guidance. Therefore, the 49 mph limit under Rule 556 reflects a balance between operational efficiency and the paramount importance of safety.