scort/trb rail capacity workshop - jacksonville florida1 1 a primer on capacity principles new...
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SCORT/TRB Rail Capacity Workshop - Jacksonville Florida
1SCORT/TRB Rail Capacity Workshop
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Rail Capacity Workshop A Primer on
Capacity Principles New Technologies Public Sector Needs
22 September 2010 1SCORT/TRB Rail Capacity Workshop
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Signal and train control functions Train control and dispatching Signal systems and equipment Capacity effects
Part 2: Conventional Signaling and Train Control Technologies- A Primer
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Signal and Train Control Functions
Ensure Safety Collision Prevention Over speed prevention (some systems)
Train operations management Set or authorize routes Manage train priorities
Advanced train control systems supplement and enhance, but do not replace these
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Facilities and Installations
Central office Dispatchers desks (work stations) Remote switching (where available) Track layout displays Support software
Office to field communications (voice radio, “code line”) Field installations
Wayside signals Switches – powered and manual Block systems Track circuits Interlockings – prevent conflicting signal and switch settings Track-train communications (where applied)
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Track Capacity Effects
Track capacity depends on the technical features of office and field systems, especially: Block system types (manual, automatic, CTC) Block lengths Use of track circuits for train detection Switch control – powered or manual Train speeds – freight and passenger
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Manual Block System (MBS)
Station A Station B
Dark Territory
Authority Limit
Manual Generation of Authorities Voice Transmission & Repeat (3-5 mins) Voice Location Reporting & Authority
Release Manual Operation of Switches by Crew Low Capacity Operation – e.g. branch lines
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Station A Station B
Automatic Block Signals
Similar to MBS, except Automatic Signals Protect Rear of Train
Roll up of Authority Automatic detection of train using track circuits
Higher Capacity Operation – applied to lower traffic main lines
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MBS With Automatic Block System (ABS)
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Consists of Signals & Switches operated by central dispatcher
Major advantage is avoiding manual switch delays
Supervisory OfficeControl and/or Indication
Remote Controlof Switches / Signals
Centralized Traffic Control
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Authority conveyed by Signal Indication Track Circuits convey train location to
dispatcher Block system protects train in block Much higher capacity Better train performance Applied to most higher capacity main lines on
US freight network outside terminal areas
Centralized Traffic Control (cont)
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Spe
ed
LoadedFreight
PassengerOr Commuter
Higher SpeedPassenger
Block Design Distance
Braking Curves – Mixed Freight and Passenger Traffic
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Block length is a function of freight train braking Typically 2 – 3 miles length
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Block A5
Signal A4Train 2
Block A3
Directionof Travel
Signal A1
Block A1
Train 1Signal A3 Signal A2
Block A4 Block A2
Block is occupied by train
Normal Speed
Zero SpeedCaution Speed
NormalSpeed
NoCode
G Y R G
Block length fixed by maximum speed, civil limits, grade, and worst train braking distance.
Wayside Signal Spacing
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Additional aspects provide finer control of train movement, at additional cost and complexity. Trains operating at different
speed limits may require different rules.
Block A6
Signal A5Train 2
Block A3
Signal A1
Block A1
Train 1Signal A3 Signal A2
Block A5 Block A2
Normal SpeedZero
Speed
G/RSignal A4
Y/G
Block A4
G/RR/R
Y/R
CautionSpeed
NormalSpeed
NoCode
AdvancedApproach
Block is occupied by train
Signal Spacing - Options
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Automatic Systems Most conventional systems rely on
engineer compliance with signals and operating rules
Automated systems provide in cab displays and may enforce compliance
Principal systems are: Automatic Train Stop – ATS
Enforce braking if engineer fails to respond to signals
Normally 8 second delay before enforcement Automatic Cab Signals - ACS Automatic Train Control – ATC Civil Speed Enforcement – NEC and some NJT
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Aspect transmitted display in engineer’s cab
Brakes apply automatically if authority is exceeded
Used on NEC, LIRR, MNCR, NJT, limited elsewhere
Direction of TravelTrain
Signal
SignalData
DataCode
CodeGenerator
Code Transmission in Rails
Code Pick-UpCoils
Speedo
BrakeInterface
Processor Signal Data
Driver’s Panel
Two types:
• Intermittent• Continuous
Cab Signals
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No changes can occur while trainis outside of limited intervals.
• Speed authorization is passed to train at limited intervals, typically at signal locations.• Train stores information until next authorization is received.
Intermittent , ATS, ACS, ATC
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• Speed authorization is continuously updated to vehicle.• Changes in speed authority can be made at any time, and are visible to operator immediately.• Capability to increase traffic; immediate recognition of aspect upgrades allow quicker response.• Loss of signal is most restrictive, stopping train.• Train requires no ‘memory.’
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Continuous ATS, ACS, ATC
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Signal A2Signal A4 Signal A1Train 2 Train 1G Y R G
Signal A3
Without ATP, Train 2 continues to slow throughout block, even though Train 1 proceeds past Signal A1.
Y
Signal A2Signal A4 Signal A1G Y R G
Signal A3
With ATP, Train 2 can resume normal speed as soon as Train 1 proceeds completely past Signal A1, increasing capacity
Y G
Train 2 Train 1
Advantages of Continuous Automatic Systems
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Home Signal - Controls entrance into interlockings.Most restrictive display is “STOP.”
Distant Signal - Last automatic signal beforea home signal. Most restrictive display is
usually “Stop and proceed.”
Intermediate Signals - Non-controlled signals other than distant signals –Aspect display cascades from next signal aspect. Most restrictive
display is “Stop and Proceed.”
Types of Signals
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Signals indicate authorized speed:
Speed Signaling Displays speed at this and next signal Turnouts speeds displayed where
applicable Requires many signal aspects Applied on the NEC
Types of Signal – Speed Signaling
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Route Signaling Displays 3 or 4 Aspects
Clear , (double Approach), Approach to Stop & Stop
Diverging route, where applicable Turnout speed is shown in timetable
Signaling indicates selected route:
Signal Systems – Route Signaling
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Minimum warning time by state regulation or FRA is 20 seconds.
>20 Seconds
Highway Crossing Protection
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20 seconds – Any Speed
Constant Warning - Grade Crossing PredictorMeasures train speed and adjusts warning for
constant warning time
20 seconds = 2933 feet at 100 MPH
20 seconds = 733 feet at 25 MPH
Fixed Track Circuit Approach - Varies with train speed
80 seconds at 25 MPH
Highway Crossing Protection
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Highway traffic signal pre-emption at nearby intersections.
When train approaches, highway traffic signals prevent turns towards crossing , while allowing cars to clear
crossing.
Highway Crossing Protection
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