Layout Design For Signaling

Layout Design For Signaling
©2014, Rodney Black June 29, 2014 7/22/2018

Layout Design for Signaling
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Outline Why Signal a Layout How the Prototype Uses Signals Signal Placement and Control Basics Automatic Block Signals (ABS) Absolute Permissive Signals (APB) Centralized Traffic Control (CTC) Right of way issues Disclaimer: much of this clinic is based on panel discussions from pervious conventions and an excellent paper by Seth Neumann and Byron Henderson 7/22/2018 Layout Design for Signaling

Why Signal a Layout Signals add Color and Animation – make the layout come alive Realism – set the layout in time and(possibly) space Operating interest – mimic the prototype Functionality – provide safety for trains and control movement They are cool! 7/22/2018 Layout Design for Signaling

Layout Signals Cosmetic (dummy) Semi-functional Fully functional on layout Fully functional with or through repeaters 7/22/2018 Layout Design for Signaling

Prototypical Signals on Layouts Every railroad had unique signal systems. Research your prototype If free lancing, there is probably an example This clinic will address generic concepts 7/22/2018 Layout Design for Signaling

How the Prototype Uses Signals Train order boards Safety overlay Interlocking plants Traffic control 7/22/2018 Layout Design for Signaling

Nomenclature Aspect – how the signal appears in the field (e.g. “red”) Name – the name of the indication (e.g. “Clear”) Indication – the meaning of the signal – how the crew should respond (e.g. “Proceed prepared to stop at second signal”) Route signals – the indication shows the path through a plant Speed signals – the indication shows the safe speed for the train before the next signal 7/22/2018 Layout Design for Signaling

Signals are about Safety Prevent a train from running into something Prevent a train from running off the rails Provide a train time (distance) to stop or adjust speed Facilitate movement 7/22/2018 Layout Design for Signaling

Basic Aspects and Indications Aspect Rule Name Indication “permissive” stop “absolute” stop ATSF example 7/22/2018 Layout Design for Signaling

Layout Design Considerations Placement Functionality Layout requirements Where appropriate 7/22/2018 Layout Design for Signaling

Train Order Boards Signals at manned stations Operator transcribes orders from a dispatcher, delivers them to the train crew, and reports train arrivals to the dispatcher The board appearances were quite unique for railroad, era, and location Simple on/off Appropriate for TT&TO (Todd Sestero) 7/22/2018 Layout Design for Signaling

Train Order Boards layout dispatcher LEDs Tortoises Servos Twin coils Orders Reports 7/22/2018 Layout Design for Signaling

Safety Overlay (Automatic Block System) Electronic checking to prevent trains from running into each other Alternative to Rule 99 (“Flag protection required against following trains on the same track”) Unbonded (detected) sidings Supplements track occupancy authorization (except for some roads) Appropriate for all operating schemes (TT&TO, DTC, TWC, CTC) 7/22/2018 Layout Design for Signaling

Safety Overlay (Automatic Block System) 7/22/2018 Layout Design for Signaling

Safety Overlay (Automatic Block System) Permissive signals No Siding Signals No siding detection Stop indication Stop indication Stop indication Occupancy Occupancy Occupancy Occupancy Uni-directional: Indications travel opposite train direction Signals show condition of track to next signal – not authority to occupy track If block is occupied then red Else if next signal red then yellow Else green Jay S. Boggess 7/22/2018 Layout Design for Signaling

Occupancy Detection Block detection (e.g. coil, diode voltage drop) Point detection (e.g. photo, magnetic reed switch) feedback detector power feedback track power Solid – no blinking Accurate – no misses, no false reports 7/22/2018 Layout Design for Signaling

Point Detectors Pros No equipment modification Precise location determination No track gaps Cons Precise location determination Sensitive alignment Trains must be longer than longest distance between detectors Hold timer? Bi-directional? Open turnouts? 7/22/2018 Layout Design for Signaling

Block Detectors Pros Prototypical Covers an area Effective Cons Gap tracks Rolling stock modifications (metal resistor wheels) Shortest block must be longer than longest distance between two resistor wheels Dirty track/wheels do not detect Place gaps at signals 7/22/2018 Layout Design for Signaling

Implementing ABS Power not shown Custom boards (FPGA) January 1992 MR Inexpensive No PC Approach lighting? R Y G Red in Yellow in Red out R Y G Red in Yellow in Red out detector detector Power not shown Commercial boards Flexible JMRI Chubb (chapter 19) detector detector Stationary Decoder Stationary Decoder Stationary Decoder Stationary Decoder PC 7/22/2018 Layout Design for Signaling

Safety Overlay (Bi-directional ABS) Does not protect well against opposing movement 7/22/2018 Layout Design for Signaling

Safety Overlay (Absolute Permissive Blocks) Electronic checking to prevent trains from running into each other – siding to siding protection for opposing moves and signal to signal protection for following moves Alternative to Rule 99 (“Flag protection required against following trains on the same track”) Unbonded (undetected) sidings Supplements track occupancy authorization (except for some roads) Appropriate for all operating schemes (TT&TO, DTC, TWC, CTC) 7/22/2018 Layout Design for Signaling

Safety Overlay (Absolute Permissive Blocks) 7/22/2018 Layout Design for Signaling

Safety Overlay (Absolute Permissive Blocks) Permissive signals Absolute signal No Siding Signals No siding detection Indication & DOT Indication & DOT Indication & DOT 4 4 1 2 Occupancy Occupancy Occupancy Occupancy 3 1 1 4 Indication & DOT Indication & DOT Indication & DOT Signals show condition of track to next signal – not authority to occupy track Trailing stop Indications travel opposite train direction; Tumbledown travels in train direction DOT is Direction of Travel (Traffic Stick) Signal determination: 1 If occupied or neighbor DOT is enter then red 2 Else if next is red and next DOT is enter then yellow 3 Else if next is red and next DOT is not enter then red 4 Else green Reverse movement protection Unoccupied: DOT is none Occupied: If neighbor DOT is exit then DOT is enter Else DOT is exit Implementation: January 1992 MR Chubb chapter 20 JMRI tumbledown 7/22/2018 Layout Design for Signaling

Interlocking Plants Protect crossings and junctions Protecting multiple routes multiplies the complexity Appropriate for TT&TO, as well as CTC CTC can be as simple as remote controlled interlocking plants connected by dark territory or safety overlay 7/22/2018 Layout Design for Signaling

Interlocking Plants 1 2 1 3 4 2 Interlocking because Opposing Signal Lock – a signal cannot clear if an opposing signal is cleared Conflicting Signal Lock – a signal cannot clear if a conflicting signal is cleared Indication (Route) Locking – a cleared signal will lock a switch Switch Indication Locking – a signal cannot clear through a fouling switch Detection Locking – a switch is locked if the track circuit is occupied 7/22/2018 Layout Design for Signaling

Signal Placement in Interlocking Plants A6T X Routes A2T→A8T A8T→A2T A4T→A10T A10T→A4T A4T→A3T→B3T→A8T A8T→B3T→A3T→A4T A6T→5T→A10T A10T→5T→A6T X X X 5T X X X A4T A10T X X X A3T X B3T A2T A8T X “Introduction to North American Railway Signaling” 7/22/2018 Layout Design for Signaling

Signal Placement in Interlocking Plants 7/22/2018 Layout Design for Signaling

Signal Placement in Interlocking Plants Routes 1→2 2→1 1→3 3→1 1→4 4→1 1→5 5→1 5 4 3 2 1 7/22/2018 Layout Design for Signaling

Signal Placement in Interlocking Plants Routes 1→2 2→1 1→3 3→1 1→4 4→1 1→5 5→1 6→4 4→6 6→5 5→6 Place signals on perimeter Add interior track circuits for parallel routes 5 4 6 3 Parallel movements 2 1 7/22/2018 Layout Design for Signaling

Centralized Traffic Control (CTC)/ Traffic Control System (TCS) Eliminates manned stations Allows fine control (micro-managing) traffic flow Control points (security elements, OS sections) are like simple interlocking plants Control points are linked with safety overlays Extension of safety overlay - “Proceed on signal indication” 7/22/2018 Layout Design for Signaling

Example CTC Control Point Exit Signal (Siding) Exit Signal (Main) Field Equipment (Vital Logic) Approach Signal Automatic (Dual Control) Switch Machine 7/22/2018 Layout Design for Signaling

Control Point Schematic Position Feedback Switch Machine A2 A1 B C Movement Trigger Block Detection Field Lock Lock output Turnout Control input 7/22/2018 Layout Design for Signaling

Prototype CTC Architecture Advanced Train Control System Telecom port Destination Source # Label Data Vital Logic Vital Logic Vital Logic Track circuit? Electrocode 7/22/2018 Layout Design for Signaling

Dispatcher Control with CTC (Alternative 1) OR Set west bound traffic 7/22/2018 Layout Design for Signaling

Dispatcher Control with CTC (Alternative 2) 7/22/2018 Layout Design for Signaling

Overlapping Protection Eastbound move Westbound move? Opposing Signal Lock propagates to first opposing signal at or after next signal in advance 7/22/2018 Layout Design for Signaling

More Complicated Indications Track speed (e.g. 49 mph) Turnout speed (e.g. 25 mph) Add second “arm” (head) Account for next signal being green, yellow, or red Excluding high speed turnouts, route based signaling is similar to speed based signaling 7/22/2018 Layout Design for Signaling

Even More Complicated Indications 3 Aspect Progression 1 2 3 4 Aspect Progression 4 1 2 3 Flashing yellow Advance signals are railroad specific! 7/22/2018 Layout Design for Signaling

Turnouts (Points, Switches)
Locks involving turnouts Indication (Route) Locking – a cleared signal will lock a switch Switch Indication Locking – a signal cannot clear through a fouling switch Detection Locking – a switch is locked if the track circuit is occupied Turnout normal Turnout reversed 7/22/2018 Layout Design for Signaling

CTC Signal Indication Dependencies Occupancy of protected track circuit(s) Next (advance) signal indication in direction of travel Next (advance) signal indication in opposing direction of travel Conflicting signal indications Alignment of protected turnouts Lock/unlock status of protected turnouts Occupancy of track circuits(s) in approach Other things (e.g. slide fence, draw bridge) Dispatcher/Towerman actions 7/22/2018 Layout Design for Signaling

CTC Implementation SE8C (1/8 of $96) C ($30) B ($30) Servo ($3) Block Detection SE8C $12 BD4 $6 QuadLN $15 Servo $3 A1/A2 $40 B $30 C $30 Total $136 A1/A2 ($40) Turnout Motor BD4 (1/4 of $24) QuadLN (1/4 of $60) Chubb chapters 24-25 JMRI CATS 7/22/2018 Layout Design for Signaling

Right of Way Issues Clearances – NMRA gauge and actual for equipment Support structures (switch machines, equipment sheds, etc.) Telephone/code poles, lines, signs, access roads Distance between signals – how long is a block? Protection from damage 7/22/2018 Layout Design for Signaling

References Introduction to North American Railway Signaling, Institution of Railway Signal Engineers, ISBN , 2009 Railroader’s C/MRI Applications Handbook, Volume 2 – Signaling Systems, Bruce Chubb, 2010 “Absolute-Permissive Block Signals”, Jay S. Boggess, Model Railroading, January, 1982 “Introduction to Signals for Your Model Railroad”, Seth Neumann, JMRI, jmri.org “Practical Guide to Railway Engineering”, American Railway Engineering and Maintenance of Way Association (AREMA), 2003 (on the Internet) “The Rule 281 Series, Volume 1 – CTC Machine Operation”, Mike Burgett, “Signaling Systems 101”, Mike Burgett, 4:00 pm, Thursday “CTC De-mystified, Parts 1 and 2”, Doug Geiger, 7:00 pm and 8:30 pm, today 7/22/2018 Layout Design for Signaling

Layout Design For Signaling

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