The Use of E-ATC as a PTC System By

Size: px

Start display at page:

Download "The Use of E-ATC as a PTC System By"

Louisa Morrison
5 years ago
Views:

1 The Use of E-ATC as a PTC System By Dale Hein, P.Eng. Hatch Mott MacDonald th Avenue SW, Suite 1250 Calgary, AB, Canada T2P-3G2 (587) dale.hein@hatchmott.com And Richard Morris Hatch Mott MacDonald 1809 Barrington Street, Suite 1009 Halifax, NS, Canada B3J-3K8 (902) richard.morris@hatchmott.com Number of words: 2865 Abstract Existing Automatic Train Control (ATC) systems satisfy some of the requirements for a Positive Train Control (PTC) system. This paper provides an overview of one approach to using an Enhanced ATC (E- ATC) system to satisfy all of the requirements for a PTC system compliant with Title 49 CFR It shall specifically identify the challenges associated with using E-ATC to functionally and reliably prevent train to train collisions, over speed derailments, incursions into established work zones and the movement of a train through a main line switch in the improper position. The paper will also elaborate on the extent to which the methodology and challenges differ from those associated with other types of approved PTC systems such as Interoperable Electronic Train Management System (I-ETMS) and Advanced Civil Speed Enforcement System (ACSES). 1 BACKGROUND The Rail Safety Improvement Act of 2008 defined the term Positive Train Control (PTC) system as a system designed to prevent train-to-train collisions, over speed derailments, incursions into established work zone limits, and the movement of a train through a switch left in the wrong position. (US Congress, 2008) These requirements were further expanded upon in Title 49 Code of Federal Regulations Subpart I To satisfy these requirements, AMTRAK is deploying the Advanced Civil Speed Enforcement System (ACSES), the 7 Class 1 freight railroads are deploying Wabtec Railway Electronics Interoperable Train Control System (I-ETMS) and other railroads are selecting a system based on interoperability requirements. The two PTC systems differ in the primary mechanism used to determine train position, with ACSES employing track-embedded transponders while I-ETMS uses Global Positioning System (GPS) information. Railroads that already have a traffic control system (more commonly known as centralized traffic control or CTC) with automatic train control (ATC), already meet some of the requirements for a PTC system. The Portland & Western Railroad has been granted a type approval (FRA-TA , (FRA, 2013)) for the use of an enhanced automatic train control system (E-ATC) to satisfy the requirement for a PTC system. AREMA

2 2 E-ATC As defined in , ATS and ATC provide a means of initiating an automatic brake application in a manner that will allow the train to stop prior to the entrance to a block: Occupied by a train, locomotive or car, Where the points of a switch are not closed in proper position, When an independently operated fouling point derail protecting main track and equipped with a switch circuit controller is not in the derailing position, When a track relay (or device which functions as a track relay) is in the de-energized position (or in its most restrictive state), or When the signal control circuit is de-energized. Automatic train control systems (as defined in ) also initiate a brake application when the speed of the train exceeds the cab signal rate communicated to the train. As employed on Amtrak (Amtrak, 2010), if the speed of the train is determined to be 3 mph or more above the speed permitted by the cab signal, an audible alarm shall sound within 1 second. A penalty brake shall be automatically applied and the traction power removed if the controls are not manipulated to cause the train to decelerate (suppressing the alarm) within 5 seconds of the start of the over-speed condition. An enhanced ATC system is further developed to mitigate hazards associated with PTC. 3 HAZARDS TO BE MITIGATED BY PTC 3.1 Hazards Mitigated by CTC with ATC The combination of a CTC system with ATC mitigates some of the hazards that a PTC system must be capable of reliably and functionally preventing: (a)(1)(i) Train-to-train collisions; (a)(1)(ii) Over-speed derailments (other than those involving temporary slow orders and speed within established work zones); (a)(1)(iv) Movement of a train through a main line switch in the improper position. The system can provide safety-critical integration of all indications of a wayside or cab signal system in accordance with (a)(2). In addition, the combination of CTC and ATC can provide an appropriate warning or enforcement of: (a)(4)(i) Derail or switch protecting access to main line not in protecting position; (a)(4)(iv) Moveable bridge not in position to allow permissive indication; (a)(4)(v) Hazard detector indicates an unsafe condition; (a)(5) Maximum speed in areas without broken rail detection. CTC can be employed to prevent these hazards through the display of a restrictive aspect (the most restrictive of stop, stop and proceed or restricted proceed indication that the signal is capable of displaying) governing entry into a block that: Is occupied by a train; Is protecting a conflicting train movement; Has a mainline switch that is not lined and locked for the route; A derail or switch protecting access to the main line (required by Additional requirements for high-speed service) not in the protecting position; AREMA

3 Contains a broken rail (subject to the limitations outlined in ); Contains a hazard detector integrated within CTC indicating an unsafe condition. In each instance, the enforcement of the restrictive signal aspect (including signals at a moveable bridge installed in accordance with ) through ATC ensures the mitigation of the hazard (a)(1)(i) is also intended to prevent collisions between trains operating over at grade railway crossings (diamonds). The table of mitigation measures included in the rule is appropriate to an E-ATC application. It is noted that the means of providing PTC for all routes over the at grade railway crossing is different than that in an I-ETMS or ACSES environment but no more technically challenging. CTC with ATC can prevent the occurrence of Over-speed Derailments resulting from exceeding Permanent Speed Restrictions (maximum speed authorized by and 236.0, civil engineering speed restrictions, and speed over switches). To enable the correct enforcement of speed restrictions, these speed restrictions must be revised so that: The zone speed or speed restriction corresponds to a speed code (or, is reduced to the next lower speed code); The limits of the zone speed or speed restriction begins at the nearest controlled signal or cut section that encompasses the limits of the zone speed or speed restriction. ATC is unable to prevent an Over-speed Derailment resulting from exceeding the speed restriction associated with a temporary slow order. Both CTC and ATC are safety-critical systems and, when implemented in accordance with FRA rules and AREMA recommended practices, they reduce the frequency of occurrence of these hazards to Improbable (as defined by AREMA C&S Manual Part ). 3.2 Hazards Requiring Additional Mitigation Features Within E-ATC Additional features are required in E-ATC to mitigate the following hazards: (a)(1)(ii) Over-speed derailments (those involving temporary slow orders and speed within established work zones); (a)(1)(iii) Incursions into established work zone limits without appropriate authority; (a)(2) Safety-critical integration of all authorities and indications of a wayside or cab signal system; (a)(4)(ii) Mandatory directive is issued with a highway-rail grade crossing warning system malfunction as required by , , or These hazards involve a temporary condition and/or require the train to be authorized to proceed in accordance with operating rules. To provide enforcement through ATC, the limits of temporary slow order, work zone or mandatory directive associated with a highway-rail grade crossing warning system malfunction must correspond to a controlled signal or cut section. The temporary slow order or speed within an established work zone must correspond to a cab signal rate. Both of these requirements are more restrictive and can result in negative operational impacts. This is one potential disadvantage of E-ATC in comparison to other PTC systems. Mitigation of these hazards is implemented by the dispatch office providing temporary speed restrictions through a command initiated by the Dispatcher. In this manner, the cab signal rate sent by the wayside signal system is altered, enforcing a 0 mph speed restriction (at the boundaries of an established work AREMA

4 zone or mandatory directive associated with a highway-rail grade crossing warning system malfunction) or the speed associated with the temporary slow order. The process flow for passing a signal displaying stop, work zones and crossing system malfunctions are discussed further below. 3.3 Restricted Speed E-ATC can enforce the maximum permissible speed for Restricted Speed however, as with all other PTC systems, it is not possible to ensure that the train is operated in a manner that is safe and consistent with the definition of Restricted Speed. 4 TEMPORARY SPEED RESTRICTIONS FROM THE DISPATCH OFFICE Employing the CTC control system to alter the cab signal rate involves a non-vital system in a safety critical process. The Portland & Western Railroad (PNWR, 2012) elected to employ an initial temporary speed restriction release request followed by a second speed restriction release request that is sent when the wayside equipment returns the correct acknowledgement indication. It is only after the second request that the vital wayside equipment releases the temporary speed restriction. It is also important for the vital wayside logic to ensure that: A temporary speed restriction does not override the normal maximum cab signal rate when it is more restrictive; Only one temporary speed restriction is sent for each block. To confirm that temporary speed restrictions are in place, the wayside signal equipment must indicate the current temporary speed restrictions to the office on periodic basis. Any mismatch in the indicated and requested temporary speed restrictions or the failure to indicate the temporary speed restrictions within the time-out interval must cause the automatic attempt to re-apply the temporary speed restrictions and generate an alarm to the Dispatcher. 5 KEY PROCESS FLOWS As with other PTC systems, there are areas where the simplest solution does not provide an adequate level of safety. 5.1 Passing a Signal Displaying Stop When a signal is displaying Stop resulting in a 0 mph speed restriction, a means of proceeding safely by the signal is required for system reliability. After first receiving authority to pass the signal displaying Stop from the Dispatcher in accordance with GCOR Rule 9.12, the simplest solution would be to have the engineman employ the stop release or no code proceed feature associated with the ATC system. This which would allow the train to proceed to the next controlled signal or cut section at Restricted Speed. Such an approach is inadequate (FRA, 2013) as a single point of failure (the decision of the crew to employ the stop release feature without authority from the Dispatcher) can lead to a collision. The frequency of occurrence would remain at Occasional or, at best, Remote. AREMA

5 5.2 Entry into Established Work Zones As E-ATC protects the Work Zone by setting the signals governing entry to stop, there is once again an issue of authorizing the train to proceed. Once again, after first receiving the authority to proceed from the Employee in Charge in accordance with GCOR Rule 15.2, the simplest solution would be to have the engineman engage the stop release feature of the ATC system and proceed at Restricted Speed. Such an approach is inadequate as a single point of failure (the decision of the crew to employ the stop release feature without authority from the Employee in Charge) can lead to a collision. It should also be noted that there are negative operational impacts associated both with the use of work zone limits as defined by controlled signals or cut sections and by only allowing the train to proceed through the Work Zone at Restricted Speed. 5.3 Highway-Rail Grade Crossing with a Warning System Malfunction As E-ATC ensures that a train will not operate over a high-way rail grade crossing for which a mandatory directive has been issued due to a warning system malfunction by setting the signals governing entry to the block in which the crossing is located to stop, there are a series of issues. As there is no mechanism of enforcing a stop at the crossing, the system is unable to facilitate compliance with (c)(3). In addition, unless the maximum speed permitted for Restricted Speed is reduced to 15 mph, the system would not be able to enforce a speed appropriate for compliance with (c)(3). As such, compliance with , , or will require the presence of an appropriately equipped flagger for each direction of highway traffic or at least one uniformed law enforcement officer providing warning before the train is allowed to proceed. When communications with a flagger has occurred in accordance with GCOR Rule A and the authority to proceed is received from the Dispatcher, the simplest solution would be to have the engineman engage the stop release feature of the ATC system and proceed at Restricted Speed. Once again, such an approach is inadequate as a single point of failure (the decision of the crew to employ the stop release feature without authority from the Dispatcher) can lead to a collision. It should also be noted that there are negative operational impacts associated both with stopping the train at controlled signals or cut sections, requiring the crossing to have warning provided only in accordance with (c)(1), and by only allowing the train to proceed through the block at Restricted Speed instead of allowing it to proceed at normal speed once the locomotive has passed the crossing when permitted by rule. 5.4 Alternatives to Stop Release Usage To provide a greater reduction in the frequency of occurrence, the Dispatcher could lift the 0 mph speed restriction by requesting the controlled signal to clear to display a Restricted Proceed Aspect. This would result in the signal system providing a valid cab signal rate to the train. Issues to be considered in the design of such a solution include the need for maintaining the temporary speed restriction request from the Dispatcher without modification; this is essential to ensuring that subsequent trains are stopped as required. The involvement of the Dispatcher in the process through the non-vital CTC control system would improve the probability of occurrence of the relevant hazards to Remote. The exact implementation would be a function of the CTC control system and cab signal equipment employed. The workload implications AREMA

6 associated with the involvement of the Dispatcher in the process would need to be reviewed to ensure that human factors issues do not offset any gains in safety. It should be noted that, since cab signal rates are transmitted through the rail, failures of the cab signal system and broken rail will result in no code being received by the train. In these instances, use of the stop release function provides a best alternative for passing the area with the defect as it does not require the ATC system to be disabled. Analysis will be needed to validate that the reduced frequency of the use of the stop release in combination with the single point of failure can produce an acceptable level of safety. Finally, it should be noted that other acceptable process flows are possible. As an example, highway-rail grade crossings could be equipped as cab signal rate cut sections, allowing the 0 mph speed restriction to be applied to the crossing by the Dispatcher. This would also allow a flagging switch operated by the railway flagger(s) at the crossing to override the 0 mph speed restriction as appropriate to the condition of the crossing warning system and the rules. 5.5 Other Process Flows and Interoperability Process flows associated with switching operations, entering main track, leaving main track and degraded operating modes need to be addressed in the PTC Development Plan and PTC Safety Plan. As these process flows will be unique to each railway s operations or may not be relevant to all railways, they will not be addressed within this paper. Interoperability also needs to be considered as an E-ATC system will not be compatible with some of the other PTC systems on the market. 6 CONCLUSIONS Enhanced ATC has been successfully proposed by the Portland & Western Railroad as system to satisfy all of the requirements for a PTC system compliant with Title 49 CFR , and, as such, it is a useful alternative to systems such as ACSES and I-ETMS. Passing signals at stop, entering work zones, and the operation of the system in conjunction with highway-rail grade crossing are problematic for E- ATC as is the case for other PTC systems. Ensuring that E-ATC satisfies the requirements for a PTC system will cause some negative operating impacts. As E-ATC does not require the complexity and cost of office to on-board segment and wayside to on-board data radio communications links or a track database, the trade-offs between these operating impacts and the simplicity of E-ATC are worth examining. 7 WORKS CITED Amtrak. (2010). Draft Specification for Single Level Passenger Cars. FRA. (2013). FRA Type Approval (FRA-TA ) for the Enhanced Automatic Train. PNWR. (2012). PNWR Positive Train Control Development Plan. US Congress. (2008). Rail Safety Improvement Act of 2008, Pub. L. No , div. A, 122 Stat AREMA

7 AREMA

8 POTENTIAL PTC SYSTEMS INCLUDE WRE INTEROPERABLE TRAIN CONTROL SYSTEM (I-ETMS) ADVANCED CIVIL SPEED ENFORCEMENT SYSTEM (ACSES) GETS INCREMENTAL TRAIN CONTROL SYSTEM (ITCS) ENHANCED AUTOMATIC TRAIN CONTROL (E- ATC) WHY E-ATC? E ATC I ETMS PREVENT TRAIN TO TRAIN COLLISIONS YES YES PREVENT CIVIL OVERSPEED DERAILMENTS YES YES PREVENT MOVEMENT OF A TRAIN THROUGH A MAIN LINE SWITCH IN THE IMPROPER POSITION YES YES PTC TYPE APPROVAL YES YES WHY E-ATC? E ATC I ETMS TRACK DATABASE NO YES HIGH ACCURACY POSITION INFORMATION NO YES REQUIRED OFFICE TO ONBOARD DATA RADIO NO YES COMMUNICATIONS WAYSIDE TO ONBOARD DATA RADIO COMMUNICATIONS NO YES THE CHALLENGES ENFORCEABLE SPEEDS DISPATCHABLE POINTS MANDATORY DIRECTIVE ASSOCIATED WITH A SPEED RESTRICTION PASSING SIGNAL DISPLAYING STOP ENTRY INTO ESTABLISHED WORK ZONE MANDATORY DIRECTIVE ASSOCIATED WITH A HIGHWAY-RAIL GRADE CROSSING SPEED INFORMATION NORMALLY CAB RATES FOR ATC ARE GENERATED BASED ON THE SIGNAL ASPECT DISPLAYED. CAB RATES CAN ALSO BE IMPLEMENTED TO ALLOW FOR THE ENFORCEMENT OF THE MAXIMUM SPEED AUTHORIZED BY AND 236.0, CIVIL ENGINEERING SPEED RESTRICTIONS, AND SPEED OVER SWITCHES. ENFORCABLE SPEEDS SPEED RESTRICTIONS CAN BE ENFORCED SO LONG AS THEY CORRESPOND TO A CAB SIGNAL RATE AS AN EXAMPLE, A RAILROAD MAY ELECT TO ASSIGN A CAB RATE FOR 20, 30, 40, 50 AND 60 MPH A DESIRED 45 MPH CIVIL SPEED WOULD THEN NEED TO BE IMPLEMENTED AS 40 MPH AREMA

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

10 ENTRY INTO ESTABLISHED WORK ZONE WHAT IF THE ENGINEMAN PRESSES THE STOP RELEASE WITHOUT AUTHORITY FROM THE EIC? THE FRA HAS CONSISTANTLY DEMANDED THAT PTC SYSTEMS EMPLOY MORE THAN A BUTTON PRESS IN THIS SITUATION THE DISPATCHER COULD MAKE A RESTRICTING SIGNAL REQUEST AND THE TRAIN COULD PROCEED ON THE CAB RATE RECEIVED MANDATORY DIRECTIVE ASSOCIATED WITH A HIGHWAY-RAIL GRADE CROSSING THERE IS NO COST EFFECTIVE MECHANISM OF ENFORCING A STOP AT THE CROSSING, AS REQUIRED BY (c)(3) COULD PLACE A 0 MPH SPEED RESTRICTION AT THE NEAREST CONTROLLED SIGNALS OR CUT SECTIONS MANDATORY DIRECTIVE ASSOCIATED WITH A HIGHWAY-RAIL GRADE CROSSING THE ENGINEMAN WOULD PRESS THE STOP RELEASE BUTTON WHEN COMMUNICATIONS WITH A FLAGGER HAS OCCURRED IN ACCORDANCE WITH GCOR RULE A AND PROCEED AT RESTRICTED SPEED THE PTC TYPE APPROVAL GRANTED FOR E-ATC DID NOT FIND THIS SOLUTION ADEQUATE IN THE LONG TERM CONCLUSIONS TO ACCOMPLISH ALL OF THE PTC OBJECTIVES, E-ATC REQUIRES THE RAILROAD TO MAKE SOME OPERATIONAL AND VELOCITY TRADE OFFS NONE OF THE CHALLENGES DISCUSSED ARE UNIQUE TO AN E-ATC SYSTEM. ACSES AND I-ETMS USERS ARE FACED WITH SIMILAR CHALLENGES FOR THOSE RAILROADS THAT CAN ACCEPT ITS LIMITATIONS, E-ATC PROVIDES BIG BENNEFITS IN TERMS OF SIMPLICITY THANK YOU AREMA

Positive Train Control (PTC) Amtrak s Northeast Corridor

Positive Train Control (PTC) Amtrak s Northeast Corridor Positive Train Control (PTC) on Amtrak s Northeast Corridor 12 July 2012, Session: Infrastructure 3 - Power Supply & Signaling Requirement for PTC The Rail Safety Improvement Act of 2008 requires that