SIGNALING PRACTICES ON PROTOTYPE AND MODEL RAILROADS

SIGNALING PRACTICES ON PROTOTYPE AND MODEL RAILROADS Bill Ataras September 30, 2013 PROTOTYPE SIGNALING PRACTICE 1. Many different types of signals A. Block signals B. Interlocking signals C. Whistles D. Bells E. Flags F. Lanterns G. Fusees H. Torpedoes I. Hand signals 2. This clinic will only include automatic block signals and interlocking signals 3. Both block and interlocking signals tell the engineer what the safe speed is for the track conditions ahead. 4. Helps trains to move faster by reducing the separation between following trains. 5. Speeds opposing movements and movements involving route conflicts. 6. SIGNALS WORK ONLY IF THE TRAIN AND DISPATCH CREWS OBEY THE RULES. MODEL RAILROAD SIGNALING PRACTICE 1. Signals and signal systems are an essential part of the model scene. All but the earliest or simplest of prototype railroads use some form of signal systems. The majority of 20 th century prototype railroads are signaled with automatic block signals and interlocked junction signals. Those of us who model such prototypes should model the signal systems they use. 2. Signals are an animated detail which adds viewing interest for both the operators and viewers of model railroads. 3. Signal systems give us the opportunity for many trackside scenic details: Signal and interlocking towers Battery boxes Relay cabinets Point activated electrical switches Trackside telephones for train crews, especially at absolute signals Trackside telegraph, telephone and signal poles and lines 4. Train detection and signaling can be used to enhance operations Allows more prototypical operations Operate hidden junctions and other track more easily Reduce conversation during operating sessions VOCABULARY 1. BLOCK - A length of track of fixed limits whose use is governed by block signals. The signals may be manually operated (mid to late 19 th century) or automatically operated (late 19 th century to present). 09/30/13 Copyright 2013, W. S. Ataras 1 of 9

2. BLOCK SIGNAL - A fixed signal located at the entrance of a block and used to govern the use of the block by trains. 3. HOME SIGNAL - A fixed signal located at the entrance of a route or block used to govern the use of the route or block by trains. 4. ASPECT - The appearance of a signal conveying an indication to an approaching train (e.g., GREEN). Note that a signal only presents a meaningful aspect to an approaching train. 5. INDICATION - The information conveyed by the aspect (e.g., PROCEED). 6. MANUAL SIGNAL - A signal whose aspect is determined by manual activation of some type of mechanism. 7. AUTOMATIC SIGNAL - A signal whose aspect is determined by automatic activation of some type of mechanism without specific manual intervention. PROTOTYPE TRACK CIRCUIT Prototype railroads use a simple circuit, at least in earlier eras, to detect both trains and malfunctions to the track or signaling equipment and present the safest possible aspect to the train crews. The primary purpose is to assure the safety of the trains and their cargo. Time simplest track circuit consists of a battery which causes a current to flow from the block exit, through the rails to a relay located at the entrance to the block. A resistor is used to limit the current to the minimum value required to activate the relay and overcome current leakage into ties, ballast and roadbed. There are other more complicated track circuits used, but the simple one shown below is typical of what is used on steam and early diesel roads. AC circuits and single rail circuits were often used on electrified roads. Note that any failure in the circuit causes the relay to drop out, displaying the STOP aspect. If the signal circuit battery fails, neither aspect is displayed. The rules say that, if no aspect is displayed, they are to act as if the most restrictive aspect were displayed. INSULATED TRACK JOINTS (4) DIRECTION OF TRAFFIC TRACK CIRCUIT RELAY TRACK CIRCUIT BATTERY & RESISTOR SIGNAL CIRCUIT BATTERY R G TWO ASPECT SIGNAL AT BLOCK ENTRY The two block circuit is used to display an aspect that indicates the condition of two blocks. The PROCEED aspect is displayed only if the next two blocks are clear; the APPROACH or CAUTION aspect is displayed if the second block is occupied; the STOP aspect is displayed if the first block is displayed. 09/30/13 Copyright 2013, W. S. Ataras 2 of 9

INSULATED TRACK JOINTS (4) DIRECTION OF TRAFFIC TRACK CIRCUIT RELAY TRACK CIRCUIT BATTERY & RESISTOR TO PRIOR BLOCK SIGNAL CIRCUIT BATTERY R Y G THREE ASPECT SIGNAL AT BLOCK ENTRY For block signaling, each block is equipped with a track circuit as shown above. Some railroads even use three or four block signaling. While the circuits are shown with color light signals, these same circuits are use with all forms of signals. Double track main line is usually signaled for one direction of travel on each track. When it is necessary to run opposed to the normal traffic, train orders are issued. Single track main line has its own set of problems. The signaling must protect for following moves, and also protect for opposing moves. This means that the entire stretch of single track main between passing tracks is considered as one block for opposing moves, and a number of smaller, normal sized blocks for trailing moves. As soon as a train leaves the passing track, the signal protecting the opposite entrance to the single track will immediately display STOP - ABSOLUTE. This will hold opposing traffic in the next passing track for the meet. For following moves, the signals display the normal aspects of STOP-APPROACH-PROCEED. This is illustrated in the next figure. 8 6 4 2 Y G R Y A R R G G A 1 3 5 7 FOLLOWING TRAINS SEE S-A-P ASPECT SEQUENCE ON SIGNALS 2, 4, 6 & 8 OPPOSING TRAINS SEE STOP ASPECT ON SIGNALS 1 & 3 SIGNAL 8 DISPLAYS APPROACH TO RESTRICT SPEED INTO SIDING JUNCTION SIGNALS 09/30/13 Copyright 2013, W. S. Ataras 3 of 9

The prototype selects the signal aspects to tell the engineer the safe speed to use over the route set up for his train. The safe speed depends mostly on track construction and condition. The Chief Engineer will consider such factors as track curvature, size of turnouts, type of frog construction, facing or trailing point, etc. From this he will determine the authorized speed for each route through a junction. PROTOTYPE DESIGN SPEED CHART FROG # SPEED USAGE 20 45 JUNCTIONS & PASSING TRACKS 16 30 PASSING TRACKS 12 25 LOW SPEED CROSSOVERS 8 15 YARDS 6 10 INDUSTRIAL TRACK CURVE 1 100 HIGH SPEED MAIN LINE 5 50 10 30 15 25 INDUSTRIAL TRACK Each signal will have a signal head for each of up to three routes. The top most head will indicate the condition of the normal speed route, the second will indicate the condition of the medium speed route, and the third head will indicate the condition of the low speed route. Each signal head indicates the condition of all routes of the associated speed. If there is no normal speed route, the top head will always indicate STOP. Only the middle and/or bottom head will indicate some form of CLEAR indication for lower speed routes. For your model layout, put yourself in the role of the Chief Engineer and determine the authorized speed for each route through your junctions. Then set up your signals to display the proper aspects. A chart of AAR aspects is included in this hand-out. Remember that, in most cases, the aspect gives information about not only the block or route a train is about to enter, but information about the following block(s) or subsequent parts of the route. Once you have determined the aspects needed for the immediate portion of the route, add one or more aspects to show the condition of the following track. Then, plan the aspects for the approach blocks to the junction. For example, if the junction has a route cleared for medium speed, the signal protecting the approach block should indicate APPROACH MEDIUM so that the engineer knows to reach the junction signal at medium speed. If you use this method for designing your junction signals, you will be doing things exactly like the prototype. In general, there may be no need to equip each signal to display all possible aspects. 09/30/13 Copyright 2013, W. S. Ataras 4 of 9

INTERLOCKING SIGNALS AND TRACK To provide protection from operator error, the prototype will usually interlock track and signals. This may be done mechanically or electrically. The system is arranged so that signals can be cleared for a route only after all switches have been set for the route and locked in position. Then, the signals for the route can be cleared and locked. If any two routes conflict, then the interlocking plant prevents clearing signals for them at the same time. Junctions are also interlocked to prevent moving a switch while it is occupied by a train. In addition, the prototype will also interlock a route so that, once a train has passed the approach signal, the route cannot be changed. They will also have time locks provided so that the route cannot be changed until the STOP aspect has been displayed for a period of time. This keeps the operator from changing the route if a train has already passed the point at which it could stop safely. A more complete discussion of this topic is a clinic in itself. I hope these few comments have given you a basic understanding of the approach used by the prototype in handling junctions and interlocking plants. SPECIAL MODEL RAILROAD SITUATIONS We can certainly provide our layouts with operating two or three aspect block signals, and even working junction signals. Just follow the guidelines above and any specific procedures used by your favorite road. But we have situations on our model railroads which the prototype really doesn t have, and we can use train detection and signaling to help us to operate our layouts. The most likely places we could do this involve forms of hidden track - junctions, holding tracks and staging yards. By installing train detection in such tracks, and providing a display which the operators can watch during operations, we can use such tracks during operating sessions as easily as visible track. The next figure illustrates a way to signal hidden holding tracks for easy operations. 4 3 2 1 2 3 4 Block Types 1. Body Blocks With Train Direction Detection (3 shown) 2. Engine Length Train Position Blocks (6 shown) 3. Yard Throat Blocks (2 shown) 4. Approach Blocks (2 shown) Track Diagram With Occupancy Lights On Panel Visible To Operators Could Have Dispatcher Controlled CTC Signals On Panel 09/30/13 Copyright 2013, W. S. Ataras 5 of 9

TRAIN DETECTION ON MODEL RAILROADS There are two basic approaches to train detection on model railroads: train running current detection and train passage detection. With the first, a circuit is installed through which the train running current for a block will pass. If the current is detected, the train is present and the block is occupied; otherwise the block is vacant. Long ago, before solid state electronic devices became as well developed as they are now, people would use a relay to detect train current. A relay coil sensitive to low currents (such as from a light bulb) and capable of handling full running current was installed in one of the track feeder wires. When a train was present, the relay would energize and its contacts could be used to switch signal lights on and off. Today, however, it is more reliable to use some type of solid state circuit to sense train currents. Linn Westcott first published his Twin-T circuit in the late 1950 s. It was a good circuit for its time, but improved circuits are available today. They work well, are very sensitive, and can be reasonably priced. The second basic technique for detecting trains is what I call the gate approach. At the entrance to a block a gate of some type is installed. It may be a reed switch buried between the rails and activated by a magnet installed on engines or cars; it may be an electrical switch activated mechanically as the train passes; or, it may be a photo-detector and light source arranged so that the passing train breaks the light beam. In each of these cases, the train is only detected as it passes through the gate. Once through, the signaling system usually has no further knowledge of the trains presence. For true train detection, I recommend using one of the solid state current sensing systems. These systems are reliable, not affected by dust or dirt (except wheel and rail dirt which also interferes with train operation), and can easily be interconnected for interlocking. When considering such circuits, think about the cost per block, the need for special power supplies, compatibility with train control systems such as DC and DCC or other command control systems, and any built in self-test and maintenance aids. All of these features will add to your ease of installation, use and overall satisfaction with your system. POWER RAIL COMMON RAIL RAIL GAPS FOR DETECTION (2) CAB SELECT SWITCHES OR COMMAND CONTROL POWER STATION TRACK CURRENT DETECTOR OCCUPIED VACANT TO SIGNAL LIGHTS OR OTHER CIRCUITS TRACK POWER COMMON FEED AND SIGNAL CIRCUIT COMMON NOTE: GAPS ARE USED IN THE POWER RAIL TO SEPARATE COMMAND CONTROL POWER STATIONS, OR TO DIVIDE THE LAYOUT INTO TRAIN CONTROL BLOCKS. Use a gate detector for more precise positioning of a train. For example, a photo-detector is a good choice for positioning hopper cars at an automatic car dumper. When planning your system, please consider my BD16 Block Occupancy Detector and TC4 Three Color Signal Controller. These modules have been designed to provide every necessary feature, and at a lower cost per block or signal than any other system I have seen. 09/30/13 Copyright 2013, W. S. Ataras 6 of 9

FOR MORE INFORMATION Signals and Signal Symbols Train Shed Cyclopedia, Charles S. Gregg The Compendium of Signals Boynton & Associates, Roger F. R. Karl Railroad Operation and Railway Signaling Simmons-Boardman Books, Edmund J. Phillips, Jr. All About Signals Trains Magazine, June-July, 1957, Kalmbach Publishing, John Armstrong The Railroad What It Is, What It Does Simmons-Boardman Books, John H. Armstrong Signaling Solution Product Manuals W. S. Ataras Engineering, Inc., Bill Ataras BD8 Block Occupancy Detector, 8 blocks MSC Master Signal Controller GCC Grade Crossing Controller GCX Grade Crossing Expander Signal Mounting Adapters Detectable Wheel Sets Please contact me for complete information about my products, or for general assistance in planning your signal system. Manuals are available for free download on our web site. Bill Ataras W. S. Ataras Engineering, Inc. 1212 Weymouth Street Westminster, MD 21158 Voice: (812) 533-1345 FAX: (708) 570-6140 Email: signalman@wsaeng.com Web Page: www.signalingsolution.com 09/30/13 Copyright 2013, W. S. Ataras 7 of 9

RULE 281 CLEAR PROCEED RULE 281 A ADVANCE APPROACH MEDIUM PROCEED, APPROACHING SECOND SIGNAL AT MEDIUM SPEED (NORMALLY 30 MPH, 1/2 MAXIMUM AUTHORIZED SPEED) RULE 281 B APPROACH LIMITED PROCEED APPROACHING SECOND SIGNAL AT LIMITED SPEED (BETWEEN MEDIUM & MAXIMUM SPEED - 45 to 70 MPH) RULE 281 C LIMITED CLEAR PROCEED AT LIMITED SPEED WITHIN INTERLOCKING LIMITS (BETWEEN MEDIUM & MAXIMUM SPEED - 45 to 70 MPH) RULE 282 APPROACH MEDIUM PROCEED APPROACHING THE NEXT SIGNAL AT MEDIUM SPEED (NORMALLY 30 MPH - 1/2 MAXIMUM AUTHORIZED SPEED) RULE 282 A ADVANCE APPROACH PROCEED, PREPARING TO STOP AT SECOND SIGNAL RULE 283 MEDIUM CLEAR PROCEED, MEDIUM SPEED WITHIN INTERLOCKING LIMITS (NORMALLY 30 MPH, 1/2 MAXIMUM AUTHORIZED SPEED) RULE 283 A MEDIUM ADVANCE APPROACH PROCEED PREPARING TO STOP AT SECOND SIGNAL; MEDIUM SPEED WITHIN INTERLOCKING LIMITS (NORMALLY 30 MPH - 1/2 AUTHORIZED SPEED) RULE 283 B MEDIUM APPROACH SLOW PROCEED AT MEDIUM SPEED, APPROACHING NEXT SIGNAL AT SLOW SPEED (NORMALLY 15 MPH - 1/4 AUTHORIZED SPEED) 09/30/13 Copyright 2013, W. S. Ataras 8 of 9

RULE 284 APPROACH SLOW PROCEED, APPROACHING NEXT SIGNAL AT SLOW SPEED. TRAIN EXCEEDING MEDIUM SPEED MUST AT ONCE REDUCE TO THAT SPEED. RULE 285 APPROACH PROCEED PREPARING TO STOP AT NEXT SIGNAL. A TRAIN EXCEEDING MEDIUM SPEED MUST AT ONCE REDUCE TO THAT SPEED. (NORMALLY 30 MPH - 1/2 AUTHORIZED SPEED) RULE 286 MEDIUM APPROACH PROCEED AT MEDIUM SPEED PREPARING TO STOP AT NEXT SIGNAL. RULE 287 SLOW CLEAR PROCEED AT SLOW SPEED WITHIN INTERLOCKING LIMITS (15 MPH). RULE 288 SLOW APPROACH RULE 289 PERMISSIVE PROCEED, PREPARING TO STOP AT MANUAL BLOCK OCCUPIED; PROCEED NEXT SIGNAL. SLOW SPEED WITHIN PREPARED TO STOP SHORT OF TRAIN OR INTERLOCKING LIMITS (15MPH). OBSTRUCTION, SPEED NOT TO EXCEED 15 MPH. QUALIFIED BY LETTER PLATE, MARKER LIGHT, SHAPE OF ARM OR A COMBINATION OF THE ABOVE. RULE 290 RESTRICTING PROCEED AT RESTRICTED SPEED (NORMALLY LESS THAN 15 MPH). RULE 291 STOP AND PROCEED STOP AND THEN PROCEED AT RESTRICTED SPEED (NORMALLY LESS THAN 15 MPH). QUALIFIED BY LETTER PLATE, MARKER LIGHT, SHAPE OF ARM OR A COMBINATION OF THE ABOVE. RULE 292 STOP STOP QUALIFYING FIXED MARKER PLATES YELLOW OR ORANGE BACKGROUND WITH BLACK LETTER AND OPTIONAL BLACK EDGE. OR USED ON THE APPROACH TO AN UPGRADE AREA SIGNIFYING THAT HIGH TONNAGE TRAINS MAY PASS A "STOP AND PROCEED AT RESTRICTED - REDUCED SPEED" ASPECT AT REDUCED SPEED WITHOUT STOPPING. YELLOW WITH BLACK EDGE ALUMINUM (SILVER) WITH BLACK EDGE OR MARKER PLATES ARE 15" DIAMETER OR 18" ON A SIDE, TYPICALLY. THEY ARE MOUNTED 18" OR MORE BELOW THE SIGNAL HEAD BUT WITHIN 9' 0" OF THE TOP OF THE RAIL. QUALIFIES ASPECT OF A SIGNAL TO INDICATE LIMITED (SPECIFIED) SPEEDS. 09/30/13 Copyright 2013, W. S. Ataras 9 of 9