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IEEE 1570-2002
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Foreword?(This introduction is not part of IEEE Std 1570-2002@ IEEE Standard for the Interface Between the Rail Subsystem and the Highway Subsystem at a Highway Rail Intersection.)A highway rail intersection (HRI) is the name given by the National Intelligent Transportation System (ITS) Architecture to a highway-rail grade crossing. The Federal Railroad Administration (FRA) defines a highway-rail grade crossing as ??a location where a public highway@ road@ street@ or private roadway@ including associated sidewalks and pathways@ crosses one or more railroad tracks at grade.?? This applies equally to whether the rail subsystem is part of the general system of freight railroads or part of the general passenger rail system including intercity passenger and commuter rail and rapid transit. The Federal Highway Administration (FHWA) defines a highway-rail grade crossing as ??the general area where a highway and a railroad??s right of way cross at the same level@ within which are included the railroad tracks@ highway@ and traffic control devices for highway traffic traversing that area.?? The FHWA continues on to define a train as ??one or more locomotives@ with or without cars@ that operate on rails or tracks and to which all other traffic must yield the right-of-way by law at highway-rail grade crossings.?? This definition also applies to either mainline railroads or rail rapid transit systems. This standard defines the interface between the railroad side and the highway side of a highway-rail grade crossing. One of the prime purposes of this interface has been to preempt traffic signal operation when a train is approaching in order to allow traffic to clear from the vicinity of the crossing. Historically@ this has been done with a voltage conveyed by a pair of wires where the absence of the voltage causes the highway traffic signal to begin its preemption operation. This interface is designed according to both fail-safe and closed-loop principles (and is required to be so designed by federal regulations). This standard prescribes a digital communications interface providing equivalent functions while maintaining the required safety attributes. Within the defined interface@ flexibility has been provided for information to be provided that has not historically been available. As a minimum@ this interface will support preemption operation as is presently done by an interconnection circuit. Future upgrades in functionality are supported by this interface but the user must be aware that this may increase the overall cost of the systems. This standard only allows for the possibility of additional functionality on either side of the interface; it does not mandate that functionality. This standard also follows the architecture defined in the National ITS Architecture. Figure INT-1 shows a typical installation of equipment at a highway-rail grade crossing. There was substantial discussion on the allocation of components within either the roadway or the railroad subsystem. Since this standard focuses on the interface between the railroad wayside equipment terminator and the roadway subsystem@ actual allocation of components is irrelevant as the interface is flexible enough to support alternative placements should they prove viable in the future. Figure INT-1 shows the predominant configuration for existing equipment (supported by existing or in-process standards). Clause 2 of this standard identifies existing standards for these interfaces. All direct digital communications between the railroad and roadway systems take place via wayside equipment terminators in the railway system and advanced transportation controllers (or highway traffic signal controllers) in the roadway system. This HRI interface standard specifies direct communications only between wayside equipment terminators and advanced transportation controllers and does not cover communications to/from/between rail operations terminators and traffic management systems@ which will be the subject of a separate standard.Wayside equipment terminators consist of numerous railway control functions such as crossing controllers@ grade crossing predictors@ event recorders@ etc. These functions typically reside in physically separate devices and communicate with one another via an internal communications network. This standard makes no assumptions about technologies used to implement any of the functions. Likewise@ the advanced transportation controller may consist of numerous roadway control functions such as vehicle presence detectors@ traffic controllers@ etc. The advanced transportation controller is the National ITS Architecture definition for the device that controls a variety of roadway functions. For this standard@ it is intended that this ATC definition also apply to highway traffic signal controllers. Like the railroad wayside functions@ these roadway functions also communicate to one another via an internal communications network. The HRI interface provides the means for control functions in either the wayside equipment terminators or the advanced transportation controllers to communicate with one another.The HRI interface can be thought of as consisting of both a virtual (logical) component and a physical component. The virtual component provides the communications channel between functions in the wayside equipment terminators and the advanced transportation controllers. This component consists of the message formats and information content that flow between the two systems. The physical component of the HRI interface facilitates the transfer of data between the internal data network within the wayside equipment terminators and the internal network within the advanced transportation controllers. This physical component acts as a bridge between these two independent networks. The virtual and physical HRI interfaces are illustrated in the point-to-point HRI interface configuration shown in Figure INT-2. The HRI physical interface may consist of either a simple point-to-point configuration as illustrated@ or as a multipoint-to-multipoint interconnection (i.e. network) of wayside equipment gateways and ATC gateways. As shown in Figure INT-2@ the HRI interface architecture consists of four functional entities:??Wayside functions: These are the functions within the railroad wayside equipment terminator that obtain@ calculate@ or otherwise generate the railroad system information that is to be transmitted across the HRI interface to the roadway system. These functions may also process data received from the roadway system over the HRI interface. There are typically multiple wayside functions within a single wayside equipment terminator.??ATC gateway: The roadway ATC gateway function is the companion function to the wayside gateway on the roadway side of the HRI physical interface. It routes incoming messages received over the HRI interface to the appropriate ATC function over the internal ATC network. Likewise@ the ATC gateway also routes outgoing messages from the source ATC function to the appropriate wayside gateway. ??ATC functions: These functions are the companion functions to the wayside functions in the railroad system. The ATC functions are the functions within the advanced traffic controller that obtain@ calculate@ or otherwise generate the roadway system information that is to be transmitted across the HRI interface to the railroad system. Likewise@ these functions may also process data received from the railroad system over the HRI interface. There are typically multiple ATC functions within a single advanced traffic controller.The selection of the protocol standards for the HRI interface was driven by the following high-level considerations:??Wayside gateway: The railroad wayside gateway function acts as both an internal router and an interface bridge controller. The wayside gateway is responsible for interfacing to the individual wayside functions within a wayside equipment terminator and routing outgoing HRI messages across the HRI interface to the appropriate ATC gateway. Likewise@ the wayside gateway function routes incoming information received from an ATC gateway to the appropriate wayside function within the wayside equipment terminator. ??Railroad and roadway system independence: Railroad and roadway data communication systems have evolved essentially independently of one another@ driven by requirements unique to their respective applications. The HRI interface architecture is specified in such a manner as to not unduly impact existing communication protocols currently used in railway and roadway data communication systems.??Multiple interface options: More than one set of protocols is specified for the HRI interface to provide equipment manufacturers the flexibility to implement the HRI interface in a manner that best fits the circumstances of a particular installation.??Cost effectiveness: The HRI interface protocols have been selected in large part due to their common use throughout the communications industry. Large market acceptance of these protocols assures availability of cost-effective hardware and software components needed to implement these protocols.??Limited system administration: The HRI interface protocols have been specified in such a manner as to limit the overall system administration required to implement data communications between wayside and ATC equipment. Given that different administrative authorities control railroad and roadway equipment@ the HRI interface architecture is designed to minimize coordination and administration (e.g.@ device addressing) of existing equipment on both sides of the HRI interface. Scope This standard defines the logical and physical interfaces@ and the performance attributes for the interface between the rail subsystem and the highway subsystem at a highway rail intersection.
IEEE 1570-2002 history
2002IEEE 1570-2002 The Interface Between the Rail Subsystem and the Highway Subsystem at a Highway Rail Intersection