Positive Train Control

Positive Train Control (PTC ) is a train control system which is developed in the United States to supplement the train control systems.

History

Studies of the 1990s have shown that it comes in mixed operation of freight and passenger traffic growing fast to security issues that can not be covered by the existing Zugsicherungsverfahren. The Pulse code cab signaling procedure was indeed provided with different extensions, both for the operation of urban rail networks as well as high-speed traffic. However, these extensions are incompatible with each other. The U.S. Congress has demanded in 2008 that by 2015 a single " Positive Train Control " system will be introduced ( Rail Safety Improvement Act, published on October 16, 2008 ). There was then still discussions since the decision an " unfunded mandates " (that is no financial support from the federal budget includes ), but the railway authority ( Federal Railroad Administration ) has clearly emphasized the positive cost -benefit ratio on 12 January 2010 the railway companies committed to implementing.

The railway authority FRA mentions in its objectives: " the establishment of a National Differential GPS ( NDGPS ) a nationwide, uniform and uninterrupted tracking system that is suitable for the operation of trains ", " improvement of the technology standards of the planning system and the Zugbetriebsysteme " and " reacting. security policies according to the current standard of the FRA. " The industry association of the track equipment AREMA describes the requirements for the Positive Train Control with the following points: Block control or collision avoidance; Speed ​​control; temporary speed reductions; Security at track work.

Implementation

, There are two methods which are under development.

On the one hand there is a radio-based train control system that communicates with the drive computers of freight trains. These have now been widely saved the route profiles, and should be lifted by radio messages with changes such as temporary speed limits and traffic on the opposite track on the respective date. A radio-based system also has the advantage of working in the "dark territories " without trackside signaling - even the track circuits can then be carried on radio releases ( Movement Authorities). Like is there already been common for the trip permit is simply notified by intercom announcements to the platoon leader, an automatic control in the travel computer is not so.

The use case without wayside signals is similar to the ERTMS regional expression in Europe, which operates in the GSM -R radio system. However, use is made in the USA on the TETRA -like APCO P25 radio system of the U.S. authorities. The position report is expected in the "dark territories " by GPS, as many routes are in any case only a single track there, and by differential GPS if necessary, the accuracy is improved, so that uniqueness is always given to the track.

However, a radio-based train control has only limitation in mixed traffic with high-speed trains and at very high clock rates. There trackside command is mandatory. In a statement, the Union of Railways AAR ( Association of American Railroads ) in this respect to the existing Acses (Advanced Civil Speed ​​Enforcement System) is referenced, that was installed by Amtrak for the high-speed rail in the Northeast Corridor (tested from 2000 to 2002 between New Haven and Boston, subsequently to Washington extended ). That system is based on eurobalises, but it is to be distinguished from the European ERTMS, as the driving terms of the Pulse code cab signaling currently have no precedence and GSM -R will be used.

In practice, three systems are in Positive Train Control on the high -density lines mesh, the pulse code cab signaling for cab signaling, beacons for position reporting and automatic track vacancy detection even with radio problems, as well as a Communication Based Train Management ( CBTM ) share for updates of the line profiles in the trip computers and movement authorities after an emergency brake ( Automatic Train Stop).

Criticism

The Positive Train Control System is particularly criticized because it relies in substantial parts not on the experience of the European Rail Traffic Management System ( ERTMS). The experience with ERTMS have revealed many difficulties, so it can not be assumed that a speedy implementation. On the other hand, was the European Train Control System ( ETCS) in the U.S. is in the criticism that it is very expensive with its rich haul equipment (compare also the reasons for the introduction of ERTMS Regional).

The implementation of PTC is already, the current estimate cost at least 10 billion U.S. dollars. At the same time purely private implementation is seen as problematic because of the Unfunded Mandates the Railway Inspectorate FRA has no influence when and which routes will be equipped with a certain extent with PTC elements, and it may lead to severe imbalances in the market, where it has been held at the old train control systems.

There are also technical limitations, as the satellite tracking may be affected by such bad weather conditions. The railway authority FRA has already confirmed that the safety distances must be increased. The European LOCOPROL / LOCOLOC project had shown earlier that with EGNOS -assisted satellite positioning alone the barriers of SIL 4 safety criteria are missed, which are necessary for train operation.