Abstract:
A system for remotely monitoring compliance with a railroad signal associated with a section of railroad track includes a remote aspect compliance subsystem for monitoring compliance with an indication for the section of railroad track represented by an aspect of the railroad signal. The remote aspect compliance subsystem selectively generates corresponding compliance messages, which are communicated via a network to server for display and processing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to Provisional Application Ser. No. 60/801,441, filed May 18, 2006. 
    
    
     FIELD OF INVENTION 
     The present invention relates in general to railroad signaling, and in particular, to aspect compliance monitoring systems and methods. 
     BACKGROUND OF INVENTION 
     Almost every railway system worldwide use trackside signals to ensure safety and maintain an orderly flow of traffic. In North America, signaling is typically implemented using green, red, and yellow electric lights a traditional signal can include a single light or multiple lights, which, depending on the given state of illumination, present a given aspect conveying a particular indication. (These signals can use individual incandescent bulbs and lenses in a single housing for each color, or use searchlight units, which change color using mechanical or electrical mechanisms in response to electrical control signals.) 
     There are a number of permissive and absolute indications that can be represented by the signal aspect. For example, in a signal employing two vertically aligned signal lights, an aspect with an illuminated green light above an illuminated green light is typically a “clear” indicating that the train crew can proceed along the upcoming block of track. In contrast, an aspect having an illuminated red light over another illuminated red typically indicates an “absolute stop” to the train crew. For a single light signal, an illuminated green light on a signal stanchion, with or without a numbered plate, is typically also a “clear” indicating that the train crew can proceed. On the other hand, a single illuminated red on a stanchion with a numbered plate typically indicates “stop and precede” at restricted speed, while a single illuminated red on a stanchion without a numbered plate typically indicates “absolute stop”. 
     Given the significant need to maintain safety by ensuring compliance with signal aspects, efficient and accurate techniques are necessary for monitoring train crew signal compliance, and particularly “red aspect” compliance. 
     SUMMARY OF INVENTION 
     The principles of the present invention are embodied in systems and methods that allow remote compliance monitoring of railroad signal aspects. According to one representative embodiment, a system is disclosed for remotely monitoring compliance with a railroad signal associated with a section of railroad track and includes a remote aspect compliance subsystem for monitoring compliance with an indication for the section of railroad track represented by an aspect of the railroad signal. The remote aspect compliance subsystem selectively generates corresponding compliance messages, which are communicated via a network to server for display and processing. 
     Embodiments of the present principles advantageously allow a railroad company to remotely monitor train crew signal compliance, and particularly “red aspect” compliance, and thereby improve safety. These improvements are accurate and very efficient to implement and operate. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a high level diagram of an exemplary networked remote aspect compliance monitoring system embodying the principles of the present invention; 
         FIG. 2  is a high level drawing of a representative section of railroad track and a pair of associated signals, together suitable for demonstrating a typical application of the system of  FIG. 1 ; 
         FIG. 3  is a more detailed diagram of the remote aspect compliance monitor shown in  FIG. 2 ; and 
         FIG. 4  is a flow chart illustrating a representative remote aspect compliance monitoring procedure according to the principles of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The principles of the present invention and their advantages are best understood by referring to the illustrated embodiment depicted in  FIGS. 1-4  of the drawings, in which like numbers designate like parts. 
       FIG. 1  is a diagram of an exemplary networked remote aspect compliance monitoring system  100  suitable for describing one possible application of the principles of the present invention. Remote aspect compliance monitoring system  100  includes a server  101  and associated electronic data storage  102 . A personal workstation or personal computer within a central dispatch or monitoring facility operates in conjunction with server  101  across a local area network (LAN)  104 . 
     In the illustrated embodiment, server  101  also communicates with a wireless communications network  105 , such as a GSM network available through a commercial wireless service provider, such as Cingular. At least one, and normally more, aspect compliance monitors  106  also communicate with wireless communications network  105 . As will be discussed in detail below, aspect compliance monitor  106  includes a wireless gateway  107  and a data processor  108 . 
       FIG. 2  is a high level diagram drawing of a section of railroad track  200  associated with a pair of signals  201   a  and  201   b . For discussion purposes, signal  201   a  is the “west” signal, which provides indications for westbound traffic, and signal  201   b  is the “east” signal, which provides indications for eastbound traffic. The designations “west” and “east” are labels for discussion purposes, and do not necessarily correspond to actual navigational directions. In the illustrated embodiment, signals  201   a  and  201   b  are single light signals having a number plate. Additionally, for discussion purposes, signals  201   a  and  201   b  are either single lamp or searchlight units capable of generating a red aspect. 
     System  100  also includes a west wheel detector  202   a  and an east wheel detector  202   b . West wheel detector  202   a  is spaced from a centerline running through west signal  201   a  by a distance d w  and east wheel detector  202   b  is spaced from a center line running through east signal  202   b  by distance d e . In the embodiment shown in  FIG. 2 , both west signal  201   a  and east signal  201   b  are disposed along the same centerline, generally shown by dashes; however, in alternate embodiments, west signal  201   a  and east signal  201   b  could be laterally offset with respects to each other. The total distance between west and east wheel detectors  202   a  and  202   b  is represented as d t  in  FIG. 2 . Although they will be discussed in detail below, generally, west and east wheel detectors  202   a - 202   b  each generate an electrical pulse when an axle of a locomotive or railcar passes over them. 
     Generally, aspect compliance monitor  106  is coupled by cables to west and east signals  201   a  and  201   b . For a locomotive traveling in a given direction, an alarm is sounded and a report is generated when a train crew fails to observe a red aspect condition on the corresponding signal  201   a  or  201   b  and/or passes through a red aspect at a speed above a predetermined limit. 
       FIG. 3  is a more detailed diagram of representative aspect compliance monitor  106  of  FIG. 2  and its interface with west and east signals  201   a - 201   b . In the illustrated embodiment, each signal  201   a - 201   b  is associated with a current transducer  301   a - 301   b . Current transducers  301   a - 301   b  detect when the corresponding signal  201   a - 201   b  transitions to or from a red aspect. For single bulb lights, current transducers  301   a - 301   b  directly detect the current flowing to the signal bulb when the red light is illuminated. For searchlight signals, current transducers  301   a - 301   b  sense the control current used to change the color of the signal light. Suitable current transducers are available from CR Magnetics, Inc., St. Louis, Mo. 
     Current transducers  301   a - 301   b  respectively connect through cables  302   a - 302   b  to corresponding west red and east red input ports  303   a  and  303   b  on aspect compliance monitor  106 . 
     The signals generated by current transducers  301   a  and  301   b  couple through ports  303   a - 303   b  to computer system  108 . Computer system  108  also receives inputs from west wheel detector  202   a  and east wheel detector  202   b  through cables  304   a  and  304   b  in corresponding input ports west prox  305   a  and east prox  305   b . In the illustrated embodiment, computer system  108   a  is a BL2600 Wolf Ethernet-enabled single board computer available from Z-World. West and east wheel detectors  202   a - 202   b  are preferably WDS 2  wheel detectors which clamp on to a rail of selected track section  200 , as generally shown in  FIG. 2 . 
     Aspect compliance monitor  106  communicates with a central dispatch office through a wireless gateway/router  109  and antenna  307 . In the illustrated embodiment, wireless gateway/router  109  is a Digiconnect WAM GSM wide area network (WAN) gateway/router. 
     Aspect compliance monitor  106  also includes an internal power supply, which is a DC to DC converter  308 . In the illustrated embodiment, DC to DC converter is a 12V to 24V converter available from Astrodyne, Taunton, Mass. 
       FIG. 4  is a flow chart of a preferred aspect compliance monitoring procedure  400  embodying the principles of the present invention. Preferably, monitoring procedure  400  is performed using aspect monitoring system  106  shown in  FIGS. 1 ,  2 , and  3 , although the principles of the present invention are not necessarily limited thereto. 
     At block  401 , operating parameters, such as the time, the total distance (D 1 ) between west and east wheel detectors  202   a  and  202   b , and the selected alarm speed are input into computer system  108 . The alarm speed represents the maximum speed a train crew may run by a signal  201   a  or  201   b  with a red aspect. West and east signals  201   a  and  201   b  are then monitored at block  402  for a change of aspect. 
     When, at decision block  403 , a change in signal aspect occurs for one or both of west and east signals  201   a - 201   b , the event is time-stamped and the new states for both of east and west signals are recorded. After the time stamp and aspect states are recorded at block  404 , or when no change of signal aspect has occurred at decision block  403 , procedure  400  continues to block  405  and wheel detectors west and east  202   a  and  202   b  are monitored for electrical pulses. 
     If no input is detected from either wheel detector  202   a  or  202   b  at decision block  406 , procedure  400  continues to loop back to decision block  403 . Otherwise, as each pulse is detected for given west or east wheel detector  202   a  or  202   b , the time is recorded. Assuming that at least one train axle crosses both detectors  202   a  and  202   b , the first detector generating a pulse is the origin detector, and the second detector generating a pulse is the destination detector. The direction of movement is determined by the origin detector  202   a  or  202   b . For example, the first axle on a westbound train will first trigger west wheel detector  202   a.    
     Pulse times continue to be recorded at block  407  as long as pulses continue to be generated for a given period of time (e.g. 30 seconds) at decision block  408 . Otherwise, when no pulses have been detected for the selected period of time it is assumed that the train has either stopped or passed by wheel detectors  202   a  and  202   b.    
     Thereafter, at decision block  409 , a determination is made as to whether the pulses for at least four axles have been detected by both east and west detectors  202   a  and  202   b . If this condition is not met, then procedure  400  jumps to block  415 , and the accumulated data are discarded. On the other hand, if at least four axles have crossed both detectors  202   a  and  202   b , then a determination is made as to whether the signal for the direction of travel is clear (block  410 ). If the aspect for signal  201   a - 201   b  corresponding to the direction of travel indicates clear, then procedure  400  again jumps to block  415  and the data are discarded. On the other hand, if the corresponding signal has a red aspect, then at block  411 , the average speed is calculated. From the calculated average speed, a determination is made at decision block  414  as to whether the calculated average speed exceeds the selected alarm speed. If it has not, then the data are again discarded at block  415 . Otherwise, at block  416 , a non-compliance event has been detected and alarm message is generated. 
     The alarm message includes such information as a time stamp; the estimated speed of the train, whether the movement was either an east move or a west move, and the total axle count. The alarm message is then sent to the central office, preferably via network  105  of  FIG. 1 . 
     The calculation of the average speed at block  411  can be performed using a number of different methods. In the preferred method, two software arrays are generated, one for the original detector and one for the destination detector. The entries in each array are indexed in accordance with the order in which pulses are received from the corresponding detector and store the time accumulated since the first pulse generated by the origin detector. Hence, the first entry in the origin array represents the time that the first pulse was generated when the first axle crosses the origin detector, and is always populated with a zero. The first entry in the destination array, which is paired with the first entry in the origin array, is populated the time the first axle crosses the destination detector. Similarly, the second entry in the origin array is populated with the time the second axle crosses the origin detector and the second entry in the destination array represents the time the second axle crosses the destination detector, and so on. 
     In the illustrated embodiment, the average speed is calculated when at least four pairs of entries have been generated (i.e. at least four axles have crossed both the origin and destination detectors, as discussed above). For each pair of entries, the difference between the populated times is taken. The average speed is then calculated by dividing the sum of all the calculated time differences by the total number of axles (i.e. the number of pairs of entries). 
     While the principles of the present invention have been described using red aspect compliance monitoring as an example, these principles are equally applicable to monitoring compliance with all signal aspects, including green and yellow. 
     Although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed might be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     It is therefore contemplated that the claims will cover any such modifications or embodiments that fall within the true scope of the invention.