NICTD Signal Aspects
|Main Line Signals||Diverging Signals||Restricting / Stop Signals|
The defined meaning the signals above is as shown in the Chicago Operating Rules Association guide (CORA), 6th Edition, dated October 1, 2007. (The signals to the right of each box are as shown in CORA, The dwarf signals to the left of each box are theoretical and not shown in CORA. Additional notes have been added to increase understanding. Rule numbers are as shown in CORA.)
NICTD uses approach lit LED signals on the majority their mainline. Siding and entrance signals are constantly lit. In locations where track layout does not require the presence of a particular color that color light is not present.
See the signal locations page for details of what signals are present at each control point and intermediate signal location.
For a detailed example of how signals are used at Gary Metro Center, see the CP 58.8 signal page.
For a detailed example of how signals are used at Michigan City Shops, see the CP 32.2 signal page.
NICTD trains also run on the Metra Electric District ... see the Metra page for a description of Metra signals and the Kensington signal page for details of signals at Kensington Interlocking.
Central Traffic Control (CTC) Signaling
Central Traffic Control allows the dispatcher to control switches, signals and ultimately trains on the line remotely from a central location. The dispatcher sets the desired position of switches and clears routes through each control point. Permission for a train to proceed over that route is communicated via the signals. If permission to proceed past a control point is not granted the signals will communicate that decision to train via a Stop indication.|
The CTC dispatcher sees a diagram of the line on their control board. The position of remote control switches and whether trains are cleared to proceed is shown on the board. The position of each train in the system is also shown on the board. The dispatcher has full control of the rail line from their central location. The computer system assisting the dispatcher operating CTC signals allows setting non-conflicting routes for multiple trains while preventing setting conflicting routes, from stopping a train when there is not enough time for a previously cleared train to stop and from changing switch positions when a route is cleared through a control point.
In addition to the dispatcher's control of "clear" or "stop", signals reflect local conditions on the line such as the indication of the next signal, track layout and obstructions on the rail ahead.
The South Shore Line uses Railcomm CTC in the Michigan City control center to control traffic between Kensington (CP 75.3) and Grandview (CP 3.0). NICTD plans to use Wabco ETMS when the entire line is converted to PTC (Positive Train Control - deadline December 31st, 2015).
Automatic Block Signaling (ABS)
With Automatic Block Signaling the signal aspects are controlled only by track conditions such as the indication of the next signal, switch settings and obstructions on the rail ahead. Prior to 2007, NICTD's South Shore Line used ABS on the entire line. The line between Kensington and Michigan City was converted to CTC is 2007. As of the end of 2011 only the final 3 miles at the end of the line in South Bend remained ABS.
When ABS was in use on the double track section of the South Shore Line the line was signaled for right hand running with no signals for running against the current of traffic. If a train had to run left hand (for track maintenance or emergency) it was not permitted to run at full track speed. The upgrade to CTC allows full speed running in either direction on either track. On single track segments of ABS when a train enters a single track segment all opposing signals until the next passing siding fall down to red. This prevents an opposing train from entering the same single track segment.
In ABS territory most signals are permissive. At passing sidings and other key locations "absolute" signals are installed on the main line. Trains reaching an absolute stop signal must stop and stay there until the dispatcher gives permission to pass that signal. non-absolute red signals can be passed but the train must proceed at restricted speed. The signals are local indicators. Dispatchers do not see the condition of switches or tracks.
Switches on ABS segments are controlled manually. The train crew must unlock and change the switches. Some switches may be fitted with an electronic lock that prevents the points from being changed without a delay that would allow an approaching train to pass. Dwarf signals on sidings indicate when it is safe for a train to exit the siding. Sidings may be equipped with spring switches which allow trains to leave sidings and continue without the train crew needing to stop and realign the switch to normal.
Prior to conversion to CTC, the South Shore used Railcom's Track Warrant Control system to control train movements on the ABS track between Karwick Rd and South Bend.
In 2009 NICTD received federal funding to convert the track east of Michigan City to CTC signaling. Construction began in 2010 and the project was completed in December 2011. Track 2 between CP 73.8 and CP 75.3 was converted to CTC in January 2012.
There is only one section of passenger track on NICTD's South Shore Line that remains not signaled, a few hundred feet of track from the end of ABS signaling in South Bend to the end of the line at the platform. This segment of track is considered a "yard track" and movements within them follow yard rules. At South Bend there is a permanent mandatory "Stop" sign just prior to the platform track switch. Trains proceed prepared to stop within half of sight distance at a maximum track speed of 5 MPH. (Normal "yard" rules allow a speed of up to 20 MPH on main line and 10 MPH on non-main line tracks, proceeding prepared to stop within half of sight distance, however in South Bend a lower speed limit has been set).|
A second "gap" in main line signaling between Carroll Ave and the east end of the yard in Michigan City was closed in November 2011. The yards at Michigan City remain unsignaled (except for the switches where they join the main) but passengers are not carried on those tracks.
The SouthShore Freight line between Michigan City and Kingsbury is unsignaled except at interlockings in LaPorte and Stillwell where the railroad crossed controls the signals. Only an approach and an absolute stop signal are present at these crossings.