may 20, 2008 train detection 1 train detection systems mid-states highway-rail grade crossing safety...

May 20, 2008 Train Detection 1

Train Detection SystemsMid-States Highway-Rail Grade Crossing

Safety ConferenceSession 4

Use of New Technology for Highway-Rail Intersections

John T. Sharkey, P.E.Safetran Systems Corp.


Standards• MUTCD Part 8 - Standard

Standard:Train detection circuits, insofar as practical, shall be designed on the fail-safe principle.


Regulations• FRA Part 234• Sec. 234.227 Train detection

apparatus. (a) Train detection apparatus shall be

maintained to detect a train or railcar in any part of a train detection circuit, in accordance with the design of the warning system.(b) If the presence of sand, rust, dirt, grease, or other foreign matter is known to prevent effective shunting, a railroad shall take appropriate action under Sec. 234.105, ``Activation failure,'' to safeguard highway users.


Train Detection Considerations

• Detection Circuit Length dependent on– Maximum speed of train

– Design warning time

– Equipment reaction and buffer time

– Clearance times

– Advance Preemption Time


Train Detection Considerations

• Method of Train Operation– Maximum Speed of Trains

– Mix of fast and slow trains

– Frequency of switching moves


Train Detection Circuits

• Three types of fundamental operation rely on train shunting track– Discrete Track Circuits

• DC Track Circuits (1871)• AC Track Circuits• AC/DC Track Circuits• Audio Frequency Overlay Track Circuits (1960’s)

– Motion Sensing Systems (1960’s)– Constant Warning Time Systems (1960’s)


MS & CWT Systems• Motion is sensed as a change in EZ• Prediction (CWT) is a function of the Rate of Change in

EZ


Motion Sensing Systems• Advantages

– Maybe appropriate on low density lines or where normal train moves are at the maximum speed

– Cost effective, no special circuitry to detect stopped train

– All active circuitry at crossing (not distributed along the track)

• Disadvantages– Longer or varying warning times– Wayside signals, etc, may cause the need for

coupling insulated joints


Constant Warning Time Systems

AREMA Definition: Constant Warning Time Device• Current :

A device used as a part of a highway-rail grade crossing warning system to provide a relatively uniform warning time.

• Proposed: A motion sensitive device capable of monitoring the speed of an approaching train and predicting the arrival of the train at the crossing to provide a relatively uniform warning time in accordance with a preset value.


Constant Warning Time Systems

• Advantages– Provides relatively uniform warning time, which

improves credibility – Cost effective, no additional special circuitry to detect

stopped train or varying speed trains– Ability to predict to downstream adjacent crossings

(DAX)– Newer systems have many enhancements

• Disadvantages– Wayside signals, etc, may cause the need for

coupling insulated joints– Wayside signals and interlockings may cause the

need for additional units


Enhancement in CWT


Recent Enhancement in CWT

• Complete crossing system - “Crossing in a box”• 6 Track system is the equivalent of having in one

integrated product without all the interconnected wiring that contains the following:– Six CWT track circuits including Intelligent Islands and 9

Prediction Processes (Prime & 8 DAXes per track)– A 40Amp Crossing Controller– CPU Event Analyzer/Recorder and I/O Module– A field-programmable Vital Radio Links for Remote Prediction– Multiple Vital Timers and Vital AND Gates– Embedded PC Display Module for diagnostics and

troubleshooting


Display Interface


Taking Tracks Out of Service

• Advanced options are available to take tracks or groups of tracks out of service to facilitate troubleshooting or track maintenance work


New Design Tools- Office Configuration Editor


Monitoring Philosophy

• The CWT reports its logic states to the Recorder for use in alarm calculations and event storage

• The Recorder monitors the actual I/O points on the back-plane of the CWT

• The Recorder receives information from the trackside equipment through its trackside sensor package


Monitoring Philosophy

• The Recorder knows what the CWT wants to do (LOGIC)

• The Recorder knows what the CWT tried to do (I/O POINTS)

• The Recorder knows what actually happened trackside (SENSORS)


Enhancements in Traffic Signal Preemption

• Preempt Health Input– Provides a “health check” of the interconnect relay in

the RR house– Forces a false activation in the rare event of a false

preemption due to an open interconnect circuit

• Traffic Signal Health Input– Provides a “health check” of the traffic system to the

RR – Forces warning system into Simultaneous Preempt in

the rare event that the traffic signals are in 4-way flash or dark


Enhancements in Traffic Signal Preemption

• Termination of Track Clearance– Advance Preempt Delay Timer

• Fixed time interval between Advance Preempt call and Warning Device Activation, so that slowing train will not cause Track Clearance green to end before Warning Devices activate

– Gate Down Indication• Second output from RR to indicate gate(s) in the

direction of traffic towards the intersection is down allows Track Clearance green to end


Loop Detectors mitigate Shunting Issues


Relative Cost of Sub-Systems AREMA 36-4 Study 2002

Relative Category Costs for non-redundant systems

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Cost Categories


Thank You!

Please Attend the RSSI Exhibition

may 20, 2008 train detection 1 train detection systems mid-states highway-rail grade crossing safety...

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