Create an account
A block or interlocking signal without a number plate, or designated by an A marker.
Automatic Block Signal System (ABS)
A series of consecutive blocks governed by block signals, cab signals, or both. The signals are activated by a train or by certain conditions that affect the block use.
A length of track:
• between consecutive block signals.
• between a block signal and the end of block system limits.
• in ATC limits the use of which is governed by cab signals and/or block signals.
A fixed signal at the entrance of a block that governs trains entering and using that block.
Centralized Traffic Control (CTC)
A block system that uses block signal indications to authorize train movements.
Current of Traffic
The movement of trains in one direction on a main track, as specified by the rules.
A fixed signal outside a block system that governs the approach to a block signal, interlocking signal, or switch point indicator. A distant signal does not indicate conditions that affect track use between the distant signal and block or interlocking signals or between the distant signal and switch point indicator. A distant signal is identified by a D.
Two main tracks where the current of traffic on one track is in a specified direction and in the opposite direction on the other.
General Track Bulletin
A notice containing track bulletin restrictions and other conditions affecting train movement.
Signal appliances that are interconnected so that each of their movements follows the other in a proper sequence. Interlockings may be operated manually or automatically.
A track extending through yards and between stations that must not be occupied without authority or protection.
Track Warrant Control (TWC)
A method to authorize train movements or protect men or machines on a main track within specified limits in a territory designated by the timetable.
Trackside Warning Detector
A device that indicates conditions such as overheated journals, dragging equipment, excess dimensions, shifted loads, high water, or slides.
A system of tracks, other than main tracks and sidings, used for making up trains, storing cars, and other purposes.
Please allow access to your computer’s microphone to use Voice Recording.
Having trouble? Click here for help.
We can’t access your microphone!
Click the icon above to update your browser permissions and try again
Reload the page to try again!Reload
Press Cmd-0 to reset your zoom
Press Ctrl-0 to reset your zoom
It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.
Please upgrade Flash or install Chrome
to use Voice Recording.
For more help, see our troubleshooting page.
Your microphone is muted
For help fixing this issue, see this FAQ.
Star this term
You can study starred terms together