A block signal is a fixed device placed at the entrance to a defined section of track (a block) that tells a train whether it may enter and proceed through that block. It governs entry and how the block will be used, so trains don’t collide by occupying the same block at the same time. In many systems these signals are also called intermediate signals. This is the best description because it reflects that the signal is a stationary, trackside authority at the start of a block, controlling entry into that block and the movement within it. The other options describe concepts that aren’t block signals: a moving signal on the locomotive isn’t how a block signal is defined; a flagger’s hand signal is a human communication method used in certain operations, not the fixed block signal; and a float in a water block is unrelated to railway signaling.

Before starting a TRAX trip, the operator must perform a thorough pre-departure safety check to confirm the train is safe and ready to operate. This means ensuring the train is in safe condition and that the route is verified, while also checking that critical systems are functioning. Specifically, doors, brakes, signaling, and communication systems should be operating properly, and any special instructions for that trip—such as work zones, temporary speed limits, or alternative procedures—should be reviewed. This approach protects riders and staff by confirming the vehicle can be controlled, stopped, and communicated with dispatch, and that the driver is aware of any conditions that could affect the trip. Starting without these checks is unsafe. Merely verifying the route and special instructions misses essential safety checks, and while asking passengers about issues is useful, it doesn’t replace the required pre-trip inspections.

Locking a switch to prevent unauthorized changes is about using a device that physically secures the switch in its current position. An Electric Switch Lock is exactly that kind of device: a lockable mechanism that fits the switch lever or handle so it can’t move until an authorized person removes the lock. This is a common safety measure during maintenance or operations to ensure the switch stays in the required position, preventing unintended changes that could affect train routing or safety. The other terms don’t describe a locking device: false occupancy deals with incorrect indications of track occupancy, dwell time is the period a train spends stopped at a location, and energize simply means applying power to a circuit.

In safety practices, when maintenance is done on traction power equipment, a tag-out system is used to clearly indicate the equipment is de-energized and must not be operated. The specific method involves placing a red tag on the equipment (often with the maintainer’s name and the reason) to warn others not to re-energize it until the tag is removed by an authorized person after proper verification. This makes the status visible to all workers and helps prevent accidental energizing during maintenance. The other options don’t fit this purpose: a panic brake is related to emergency stopping, a route selector is about choosing train routes, and right-of-way refers to the track area; none describe the warning method used to mark de-energized equipment.