Positive train control

Metrolink train 2016 with sticker that indicates the new equipment with the system: "PTC - Equipped With Positive Train Control Technology"

Positive Train Control ( PTC ) is the term in the USA for a uniform, modern train control system . It is the nationwide standardization of the FRA railway authority on the basis of several incompatible existing systems. The functional development goal is analogous to ETCS in the EU . The technical implementation differs, however, in the areas of route, vehicle and communication. There is de facto standardization for the introduction of digital train radio with PTC radio on 220 MHz.

history

Studies in the 1990s had shown that in the mixed operation of freight traffic and increasingly fast passenger traffic, safety problems arise that could not be covered by the train protection procedures of the time. The Pulse Code Cab Signaling process was provided with various extensions for both the operation of light rail networks and high-speed traffic, which are, however, incompatible with one another. In 2008, the US Congress demanded that a uniform Positive Train Control System be introduced by 2015 ( Rail Safety Improvement Act 2008 RSIA, published on October 16, 2008). There were discussions afterwards, as the decision is an "Unfunded Mandate" (i.e. it does not include any financial support from the federal budget). However, on January 12, 2010, the FRA railway authority clearly emphasized the positive cost-benefit ratio and obliged the railway companies to implement it.

The railway authority FRA mentions in its objectives

• "Establishment of a National Differential GPS (NDGPS) as a nationwide, uniform and uninterrupted location system that is suitable for train operations",
• "Improvement of the technical standard of planning and train operation systems" and
• "Implementation of security guidelines according to the current FRA standard".

The industrial association of track equipment suppliers AREMA describes the requirements for the PTC with the following points:

• Block control or collision avoidance,
• Speed ​​control and temporary speed reductions,
• Safety when working on the track.

Shortly after the Rail Safety Improvement Act 2008 was passed , several approaches competed for the implementation of the requirement as a PTA system. In the spring of 2009 there were eleven PTC projects at nine different railroad companies in 16 states. To promote standardization, UP , BNSF , CSX and NS founded the Interoperable Train Control Committee (ITC). This then specified the message formats , braking curves , hardware platform and the use of the 220 MHz band.

In a 2012 statement to Congress, the FRA identified two existing systems that could be used as the basis for a PTC system. These included the Advanced Civil Speed ​​Enforcement System (ACSES) from Amtrak , and the I-ETMS ( Interoperable Electronic Train Management System ) defined by the supplier Wabtec . Basically, the technology of the European ETCS was considered a suitable basis for the PTC system, but it was only discussed for the routes of the California High-Speed ​​Rail . Similar to ETCS communication typically takes place with GSM-R , ETCS components should then be connected to PTC radio for communication. Some existing systems that would actually meet the requirements of a PTC system have to be replaced later. In particular, the Electronic Train Management System (ETMS) from Wabtec is incompatible with the I-ETMS and existing locomotives must be converted. The Communication-Based Train Control (CBTC) of the Port Authority Trans-Hudson (PATH) is considered to be similar to the ACSES and can be supplemented. Other companies use the display from the I-ETMS range for retrofitting the locomotives, which results in de facto standardization. The I-ETMS display is installed in addition to the existing display, such as the PCCS display. In terms of track equipment, the ACSES radio stations transmitting at 900 MHz were again supplemented by additional transmitters for the freight trains operating at 220 MHz PTC radio.

The original target of achieving nationwide use of PTC systems on routes with mixed traffic of freight trains and passenger trains by the end of 2015 was not achieved. It is true that Metrolink (Los Angeles) took the first track with PTC into operation in February 2014, but had the previous supplier ARINC through a direct contract with Wabtec replace to provide during the year 2015, the total power and the locomotives still in time with PTC to . In June 2015, only seven companies that are organized in the Association of American Local Transport Companies ( APTA ) announced that they would make the date. At the beginning of 2017, nationwide only 456 miles of routes were fully equipped. By the end of 2018, at least 50% of the routes for passenger traffic should be in PTC operation.

implementation

Overland and branch lines

It is based on a radio-based train control system that communicates with the travel computers of the (freight) trains. These have already extensively saved the route profiles and should be notified of changes such as

• temporary speed restrictions and
• Traffic on the opposite track

be kept up to date. A radio-based system also has the advantage of functioning in the "dark territories" without signaling on the track - even track vacancy reports can then be made via radio releases (movement authorities). Something similar is already common there, but the travel permit is simply sent to the train driver by means of voice announcements; automatic control in the trip computer is not possible.

The application without line signals is comparable to ERTMS Regional (a variant of ETCS Level 3 ) in Europe, which works with GSM-R as a radio system. However, in the USA the TETRA -like APCO-P25 radio system of the US authorities is used. The position report in the "dark territories" should be done by GPS , especially since many routes there are only single-tracked anyway, and if necessary the accuracy is improved by differential GPS so that the track is always clear.

High-speed lines and metropolitan areas

The exclusively radio-supported system does not meet the requirements for high-speed traffic and mixed traffic with frequent trains. A line-side train protection is mandatory there. In a statement by the AAR ( Association of American Railroads ) reference is made to the existing ACSES, which was installed by Amtrak for high-speed traffic in the Northeast Corridor (tested 2000-2002 between New Haven and Boston , subsequently extended to Washington ). The ACSES system is based on Eurobalises , the signal aspects of which, however, differ from the European ETCS. The driving terms of the Pulse Code Cab Signaling currently have priority and GSM-R is not used.

In practice, Positive Train Control uses three systems on the highly frequented routes:

• Pulse Code Cab Signaling for cab signaling,
• Balises for position reporting and automatic track vacancy detection even in the event of radio problems,
• Communication-Based Train Management (CBTM), etc. a. for updates of the route profiles in the trip computers and driving releases after an emergency brake .

Radio standards

Several proposals have been made for the radio frequency of the PTC radio, including a multi-band solution to the Association of American Railroads' Advanced Train Control System (ATCS) with multiple frequencies at 160 MHz and 900 MHz (the old EMTS used 160 MHz, ACSES used 900 MHz). However, this introduction was stopped when the frequency of 220 MHz for national freight traffic was anchored in the Rail Safety Improvements Act of 2008 through the operation of the FRA . This frequency is based on a private initiative of two railway companies that founded a joint company PTC 220 LLC in 2007 in order to buy rights in this frequency spectrum . The other Class 1 AAR freight railways later participated and made some of the frequencies of their operating radio available. Some of the PTC-220 frequencies are available nationwide (18 channels in the 220–222 MHz range), others can currently only be used regionally (in the 217–220 MHz range). Since in some cases the spectrum will not be sufficient (20–40 channels are required regionally), FRA and railway companies are in the process of relocating other uses in order to provide more frequencies for freight traffic with PTC. Another difficulty is that in Canada the upper 1.25 meter band (222–225 MHz) is still completely available for amateur radio , but more bandwidth could be drawn from this frequency range.

Communication protocols

The transport level of the message exchange was determined under the leadership of the company Meteorcomm . They provided a Software Defined Radio Module (MCC SDR) at an early stage , which was used in locomotives, on signals and in interlockings to test the radio paths. Meteorcomm has also set up the Interoperable Train Control Network (ITCnet), which connects the operations centers of all major railway companies in the USA. The ITCnet also has interfaces to the radio network (ITCR - 220 MHz ITC Radio Network), the systems of the Systems Management Framework (ITCSM) and other transport channels (IP, 3G, satellite, WLAN). The ITC messaging (ITCM) protocol stacks allow all systems to be linked regardless of the type of connection used. Apart from the ITCR radio interface, the ITC messages are provided with an Edge Message Protocol header (EMP) for transport through an IP network. The EMP / IP messages can be distributed point-to-point (Class D - TCP / IP) or using a message broker (Class C - AMPQ ).

For addressing, IDs in the format of the existing ACSES definition are used in the EMP header for all trains. This allows direct further use of the ACSES track equipment. The ACSES trains receive shares and temporary speed restrictions ( Temporary Speed Restriction , TSR) by radio (no use of transparent data balises). The main difference to messages via I-EMTS-PTC radio is that in ACSES areas the location information relates to distances to the nearest balise, but otherwise to GPS coordinates.

criticism

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

The Positive Train Control System is particularly criticized because it does not rely on the experience of the European Rail Traffic Management System (ERTMS) to a large extent . The experience with ERTMS has revealed many difficulties which made such rapid development, testing and implementation (planned for 2009–2015) unlikely. On the other hand, the European Train Control System (ETCS) in the USA was criticized at the beginning of the legislation for being very expensive with its extensive line equipment (e.g. ETCS Level 1 Modus Full Supervision (FS) in Spain ). No operational experience and no secure standards were available for the "LowCost" version of ERTMS Regional .

PTC is estimated to cost more than $ 10 billion to implement. At the same time, the purely private implementation is viewed as problematic. Due to the unfunded mandate , the FRA railway supervisory authority has no influence on which routes are equipped with standardized PTC elements and when. Sticking to the old train control systems could therefore lead to market foreclosure and thus to considerable imbalances.

There are also technical limitations, as poor weather conditions can affect satellite positioning. The FRA railway authority has confirmed that the safety distances will then have to be increased. The European LOCOPROL / LOCOLOC project had already shown earlier that with EGNOS- supported satellite positioning alone the limits of the SIL 4 safety criteria that are necessary for train operation are missed.

See also

• KLUB-U - Russian train protection with integration of GLONASS satellite positioning and electronic route maps

Individual evidence

1. ↑ ^{a b} Archived copy ( memento of the original from January 19, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. 
2. ↑ ^{a b c} "Railroad Research and Development Program - Section 4.6 Train Control" ( Memento of the original from September 14, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , Federal Railroad Administration: Freight Railroading, "Objectives of this program will be: (*) To apply the state of the art of safety review and assurance for safety-critical systems within the FRA's regulatory environment. (*) To deploy the Nationwide Differential Global Positioning System (NDGPS) as a nationwide, uniform, and continuous positioning system, suitable for train control. (*) To advance the state-of-the-art in tactical and strategic planning and railroad network control systems. " 
3. ↑ http://www.arema.org/eseries/scriptcontent/custom/e_arema/comm/c37/05-01-08/AREMA_MP_23-2-1_New_2008_Mar_F.doc
4. ↑ ^{a b} Positive Train Control - White Paper . Transit Wireless Communications. May 2012. Archived from the original on June 11, 2016. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved May 23, 2016. 
5. ↑ ^{a b} Positive Train Control - Implementation Status, Issues, and Impacts . Federal Railroad Administration. August 2012.
6. ^ Dan Weikel: Metrolink to replace contractor to avoid train control project delays . In: Los Angeles Times . 23rd January 2014.
7. ↑ James Rainey: 'Positive Train Control' ordered by Congress, but not yet in place . NBC News, Dec. 19, 2017.
8. ↑ http://www.aar.org/NewsAndEvents/PressReleases/2008/09/092408_Statement_on_railsafety_bill.aspx  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.  
9. ^ PTC-220 LLC, Overview. (PDF) National Transportation Safety Board, USA, February 26, 2013, accessed January 24, 2017 . 
10. ↑ PTC on Amtrak? . Federal Railroad Administration. Retrieved June 22, 2016.