Abstract:
A method and apparatus for actuating a train horn use the speed of the train to determine when to start a horn sequence such that the horn sequence complies with all applicable regulations. In one embodiment, an engineer enters a command, such as by pushing a button, when a predetermined distance from a grade crossing is reached. A processor then determines the speed of the train from a tachometer. The speed is used to determine how long it will take to reach the grade crossing. Preferably, this calculation is repeated until the time to reach the grade crossing is within a window during which the horn sequence must be started. The processor or other device then causes the horn to sound in the required pattern.

Description:
BACKGROUND 
       [0001]    The Federal Railroad Administration (FRA) promulgates regulations for the operation of railroads in the United States. The FRA has promulgated regulations for the sounding of locomotive horns at grade crossings. The regulations, which can be found at 49 C.F.R. § 222.21, require the locomotive horn to be sounded in a particular pattern, sometimes referred to as a “15L” pattern. The pattern may be described generally as two long horn blows followed by one short horn blow followed by one long horn blow. The regulations further require that only one iteration of this pattern be sounded when passing a grade crossing. The regulations still further require that the pattern begin no more than one quarter mile (1,320 feet) prior to the grade crossing. This location is marked by a “whistle board” to inform the engineer when the location has been reached. When the train is traveling greater than 45 mph, the regulations require the engineer to start blowing the horn in the aforementioned pattern at the whistle board (those of skill in the art will recognize that one quarter of a mile will be traveled in 20 seconds at a speed of 45 mph). However, when the train is traveling less than 45 mph, the engineer is required to blow the horn 15-20 seconds before reaching the grade crossing, but not prior to the whistle board. 
         [0002]    Engineers have had difficulty complying with these regulations. Engineers sometimes miss the whistle board and fail to sound the horn at all or sound the horn late. Even when the engineer is aware of the whistle board, it has proven difficult for the engineer to ensure that the sequence starts 15-20 seconds before the crossing is reached and continues until the lead locomotive has passed through the grade crossing while maintaining the proper duration for all on and off portions of the pattern. 
         [0003]    Engineers sometimes blow the horn excessively to ensure that the horn is sounding through the grade crossing as a matter of safety. This is perhaps a result of litigation in which engineers and the railroads that employ them have been accused of causing accidents at grade crossings due to alleged failures to sound the horn or to sound the horn in a manner that provided sufficient notice of the approach of the train. However, excessive horn blowing has led to many noise complaints from residents in the area of the grade crossings. In response to these complaints, the FRA has imposed fines for excessive horn blowing that does not comply with the aforementioned regulations. 
         [0004]    Horn sequencers have been developed to help engineers comply with these regulations. Horn sequencers are devices that, when activated, will produce a single iteration of the horn pattern mentioned above. These devices ensure that the durations of the one and off periods of the pattern are correct. An example of such as device is the 54000 series event recorder sold by Bach-Simpson. However, these devices do not help the engineer determine when to start the pattern. When the train is traveling at speeds below 45 mph, the engineer must estimate when the train is 15-20 seconds from the grade crossing and then activate the horn sequencer. 
       SUMMARY 
       [0005]    The aforementioned issues are addressed to a great extent by a method and apparatus in which the speed of the train is used to determine a delay which precedes the start of a horn sequence such that the horn sequence complies with all applicable regulations. In one embodiment, an engineer enters a command, such as by pushing a button, to start a horn sequence when a predetermined distance (e.g., as indicated by a whistle board) from a grade crossing is reached. A processor or other device then determines the speed of the train from a device such as a tachometer. The speed is used to determine how long it will take to reach the grade crossing. Preferably, this calculation is repeated at a rapid rate (e.g., every quarter second) until the time to reach the grade crossing is within the range at which the horn sequence must be started. The processor or other device then causes the horn to sound in the required pattern. Such embodiments have the advantage of simplicity and a corresponding low cost, but rely on the operator to enter the command at the predetermined distance. In other embodiments, rather than relying on an operator to enter a command to inform the system that the predetermined distance, a combination of a global positioning system and a database that contains locations of the predetermined distances is used to determine when the predetermined distance has been reached. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The aforementioned advantages and features of the present invention will be more readily understood with reference to the following detailed description and the accompanying drawings in which: 
           [0007]      FIG. 1  is a block diagram of a horn activation system according to one embodiment. 
           [0008]      FIG. 2  is a flowchart of the processing performed by the system of  FIG. 1 . 
           [0009]      FIG. 3  is a block diagram of a horn activation system according to a second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    In the following detailed description, a plurality of specific details, such as specific regulations for horn activation, are set forth in order to provide a thorough understanding of the embodiments discussed below. The details discussed in connection with these embodiments should not be understood to limit the present invention. Furthermore, for ease of understanding, certain method steps are delineated as separate steps; however, these steps should not be construed as necessarily distinct nor order dependent in their performance. 
         [0011]    The present invention is believed to be particularly well suited for use in the railroad industry and hence will be discussed primarily in that context herein. The present invention should not be understood to be so limited and may be used in any situation at which it is necessary to sound a horn or other warning device on a vehicle at a predetermined location and/or in a predetermined sequence. 
         [0012]    Referring now to  FIG. 1 , a system  100  according to one embodiment includes a processor  110  connected to a switch  120 . The processor  110  may be any type of logic unit, including hard wired logic units and programmable logic units (e.g., microprocessors) and may include one or more input and/or output ports (which may be separate physical ports or logical ports implemented as a single physical port) for connection to external devices. The switch  120  is preferably of the momentarily closed variety and preferably takes the form of a button that an operator may press. When the system  100  is installed on a train, the switch  120  is preferably installed on or near a control panel in the cab of a lead locomotive. Also connected to the processor  110  is a tachometer  130 . The tachometer  130  outputs a signal indicative of the speed of the train. The specific device used to indicate the train&#39;s speed is not important and a device other than a tachometer is used in other embodiments. For example, in some embodiments, the voltage across a DC traction motor or the frequency driving an AC traction motor on a locomotive is used to determine the speed of the train. A horn  140  is also connected to the processor  110 . The horn  140  is typically an air horn and is suitable to produce an audible sound sufficient to warn motorists and pedestrians of the train as it approaches a grade crossing. 
         [0013]    A flowchart  200  of the operations performed by the system  100  in some embodiments is illustrated in  FIG. 2 . The processor  110  determines whether the switch  120  has been depressed at step  202 . If no switch depression has been detected at step  202 , the step is repeated until a switch depression is detected. (Those of skill in the art will recognize this implementation as employing a polled technique and will readily understand that implementation as an interrupt service routine or other implementations are also possible). As discussed above, an operator of the train will be instructed to depress the switch  120  when the train reaches a location one quarter mile away from the grade crossing as indicated by a whistle board. Thus, the detection of a switch depression at step  202  signifies to the processor  110  that the train is now one quarter of a mile from the grade crossing. 
         [0014]    The processor  110  next obtains the speed of the train and the current time at step  204 . The speed may be obtained from the tachometer  130  or any other device on the train that is capable of reporting speed. The time may be obtained from a clock maintained in the processor  110 . If the speed is greater than 45 mph at step  206 , the processor starts the “15L” horn sequence at step  212 . In the embodiment shown in  FIG. 1 , the processor  110  is connected to activate the horn  140  directly (those of skill in the art will recognize that a relay may be present between the processor  110  and the horn  140 ) and therefore the processor  110  outputs a signal having a time varying pattern corresponding to the “15L” pattern. In alternative embodiments such as the system  300  shown in  FIG. 3 , a horn sequencer  141  may be present between the processor  110  and the horn  140 . In such embodiments, the processor  110  need only output a start signal to the horn sequencer  141 , and the horn sequencer  141  generates a driver signal having the “15L” pattern to drive the horn  140 . 
         [0015]    Referring now back to  FIG. 2 , if the speed of the train is less than 45 mph at step  206 , the processor  110  calculates at step  208  the time in which the train will reach the grade crossing using the train speed obtained in step  204 . If the time is less than a threshold corresponding to a time at which horn sequence is to start (e.g., 17.5 seconds) at step  210 , the horn sequence is started at step  212  and the process ends when the horn sequence has completed. 
         [0016]    If the time in which the train will reach the grade crossing is greater than the threshold at step  210 , the processor  110  then delays for a short period of time (e.g., a quarter of a second) at step  214 . Next, the processor  110  calculates a new train position at step  216 . The new position of the train is calculated by calculating the difference between the current time and the time obtained at which the previous train position was calculated, and multiplying the difference in time by the current speed of the train as reported by the tachometer  130 . Preferably, the delay period of step  216  is short relative to the maximum possible acceleration/deceleration of the train. Step  208  is then repeated using the updated position and time from step  214 . 
         [0017]    The embodiment discussed above in connection with  FIG. 2  employs a relatively simple algorithm that is simple to implement but suffers from a somewhat decreased accuracy. Those of skill in the art will recognize that more sophisticated algorithms that determine and account for train acceleration may also be employed. 
         [0018]    Those of skill in the art will also recognize that the embodiment described above relies on a train operator or some other personnel onboard the train to activate the switch  120  to signal to the processor  110  that the train has reached a location one quarter of a mile in advance of the grade crossing. Such embodiments, while advantageous in that they minimize necessary additional onboard and wayside equipment suffer from the drawback of reliance on a human being. In some other embodiments, wayside equipment such as a transponder or an axle detector may be used to send a signal to the processor  110  to indicate that the train has reached the quarter mile location. Such embodiments have increased reliability, but also require additional wayside and onboard equipment (i.e., a receiver to receive the signal from the wayside equipment) and a corresponding increase in cost. 
         [0019]    In other embodiments, an onboard position system such as a global positioning system (GPS) receiver is used to determine the train&#39;s position and a database that contains positions of grade crossings is used to determine when the train has reached a location a quarter mile prior to the grade crossing. Such a system is described in commonly owned U.S. Pat. No. 6,609,049, the contents of which are hereby incorporated by reference herein. The GPS receiver may also be used to determine speed, but a tachometer is generally more accurate. 
         [0020]    In some of the embodiments discussed above, the lengths of the long horn blasts are the same throughout the “15L” pattern. In other embodiments, the last long blast is slightly longer than the first two long horn blasts to increase the likelihood that the horn will be sounding at the moment the locomotive reaches the grade crossing. In still other embodiments, there is a minimum speed below which the system will not sound at all, which relies on the operator to sound the horn in accordance with the situation. For example, if a train is traveling extremely slowly (e.g., 1 mph), sounding the horn 20 seconds before the grade crossing is reached will result in the horn blowing for the first time when the train is very close to the grade crossing, which may startle a motorist or pedestrian in the grade crossing. 
         [0021]    Various embodiments of methods and systems for activating a warning device on a train have been discussed above. It should be understood that the detailed description set forth above is not intended to limit the present invention and that numerous modifications and changes to the specific embodiments set forth above can be made without departing from the spirit and scope of the invention. Rather, the present invention is only limited by the following claims. 
         [0022]    Further, the purpose of the Abstract of the Disclosure is to enable the U.S. Patent and Trademark Office and the public generally, and especially the scientists, engineers and practitioners in the art who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of the technical disclosure of the application. The Abstract of the Disclosure is not intended to be limiting as to the scope of the present invention in any way.