Signals, Interlocking, and Track Safety
What this domain tests
Signals, Interlocking, and Track Safety tests signal aspects, interlocking routes, switch protection, trip stops, fouling points, third-rail hazards, and work-zone protection. Expect questions about what a signal authorizes and where it is safe to walk or stand.
Signals and interlocking
- Automatic signals divide track into blocks and generally govern following movement; interlocking or home signals govern routes through switches and crossing tracks.
- An interlocking is a plant of switches and signals controlled from a tower or console. Once a route is set, conflicting routes are locked out.
- A call-on or restricting indication may allow movement into an occupied or restricted area at restricted speed; it does not authorize normal speed.
- A trip stop is a wayside device that applies emergency braking if a train passes a signal at stop. Do not pass a stop signal and then try to reset the trip; follow the rule and notify control.
Track safety
- Know the fouling point: the location where a person or train standing on one track would be struck by movement on an adjacent track.
- The third rail carries traction power. Treat every rail and every conductor as energized until power is removed and confirmed by the person authorized to do so.
- In work zones, look for flaggers, lights, and posted limits; never assume a work crew has seen or heard your train.
Worked example
An interlocking signal displays a restricting indication. You may proceed only at restricted speed, prepared to stop short of any train, switch, or obstruction, and you must keep looking for a stop signal ahead. The indication does not mean the route is clear for normal speed.
Traps
Reading a restricting signal as clear; ignoring switch position; standing inside the fouling point while inspecting; and stepping over the third rail instead of using the protected walkway.