In a controlled block, what governs the limits of the block?

The limits of a controlled block are governed by block limit signals and cab signals. These signals are critical components of the railroad signaling system and are specifically designed to define the boundaries of each block, ensuring safe train operations.

Block limit signals indicate whether it is safe for a train to enter a block or whether it must wait. When a block is occupied by a train, the signals will communicate to subsequent trains that they must halt to prevent collisions. Cab signals work in conjunction with these block limit signals by providing real-time information to the train engineer about the status of the blocks ahead, allowing for safe and efficient train control and movement.

This system reduces the risk of accidents and enhances overall operational safety by providing clear, visual, and auditory confirmation of track status. Proper understanding and use of these signals are essential for locomotive engineers to manage train speeds and maintain safe distances between trains effectively.

The other options involve factors that may influence train operations but do not specifically set the limits of a controlled block. Factors such as track conditions, train schedules, and passenger demands play roles in overall train management and efficiency but do not directly define the boundaries of controlled blocks.