CNW Passenger train headed west, 1960

Passenger train on westbound CNW main line approaching an interlocking signal which is on the left side of the engine. This signal governs all westbound main line movements through this interlocking plant, regardless of whether the movement be passenger train, or yard movement destined for the Proviso yards. In this situation, with the cab of the engine forward, the signal will pass from the view of the engineer when it is within 30 feet or so of the engine. Without a fireman on the left looking out from his side of the engine, the engineer can never be certain that a signal has not changed after it has passed from his view.