Abstract:
A method and system for automatically activating a train warning device that uses a positioning system such as a global positioning system (GPS) receiver or an inertial navigation system (INS) to determine the train&#39;s position. The system further includes a database containing locations of grade crossings and other locations at which a train is required to give a warning signal and what regulations govern activation of the warning device at such locations.

Description:
This application claims priority and is a Continuation of U.S. patent application Ser. No. 10/184,929 filed Jul. 1, 2002, now U.S. Pat. No. 6,609,049, issued Aug. 19, 2003. The entirety of this patent is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to automated railroad operation generally, and more particularly to a system and method for automatically activating a train warning device at a location for which a warning is required or desirable, such as a grade crossing. 
     2. Discussion of the Background 
     More than 4,000 collisions between trains and vehicles occur at public and private highway-rail grade crossings every year, resulting in more than 400 deaths annually. Approximately 50% of these accidents occur at grade crossings with active warning devices such as bells, flashing lights, and/or gates. Recently, some state and local governments enacted legislation prohibiting the use of horns at certain location and/or times. The Federal Railroad Administration (FRA) has studied the effect of this legislation. As a result of this study, the FRA determined that the sounding of train horns significantly reduces accidents at grade crossings. 65 Federal Register 2230 et seq. 
     As a result, the FRA promulgated several regulations, including 49 C.F.R. § 222.21, which regulates how and when horns are to be sounded. Under 49 C.F.R. § 222.21, in the absence of a state regulation, a horn must be sounded starting at a position no greater than ¼ mile away from the grade crossing. Furthermore, the railroad must place a whistle board (a wayside sign telling the conductor to begin sounding a horn) at a location such that a train traveling at the maximum speed will begin sounding its horn 20 seconds before the crossing, or the railroad must ensure by other methods that the horn is sounded no less than 20 seconds, but not more than 24 seconds, before the locomotive enters the grade crossing. If a state regulation is currently in place, the rule does not disturb the state regulation until a change in the maximum allowable speed is made, at which time the requirement of 49 C.F.R. § 222.21 become effective. It will be readily apparent from the above discussion that precisely determining when to begin sounding a train horn is not a trivial task. 
     Even if a device such as a whistle board is present to inform an engineer as to the precise location to begin sounding a train horn, engineers sometimes make mistakes and don&#39;t begin sounding the horn at the right time. In many court cases brought against the railroad operator relating to grade crossing accidents, the engineer is accused of causing the accident by failing to blow the horn correctly. 
     What is needed is a method and system that will automatically activate a horn in a prescribed manner at an appropriate place and time. 
     SUMMARY OF THE INVENTION 
     The present invention meets the aforementioned need to a great extent by providing a method and system for automatically activating a train warning device that uses a positioning system such as a, global positioning system (GPS) receiver or an inertial navigation system (INS) to determine the train&#39;s position. The system further includes a database containing locations of grade crossings and other locations at which a train is required to activate a warning device, as well as what regulations govern activation of the warning device at such locations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the invention and many of the attendant features and advantages thereof will be readily obtained as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
     FIG. 1 is a logical block diagram of a train control system according to one embodiment of the invention. 
     FIG. 2 is a flowchart showing an automatic horn sounding method according to one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention will be discussed with reference to preferred embodiments of train control systems. Specific details, such as regulations, distances and times, are set forth in order to provide a thorough understanding of the present invention. The preferred embodiments and specific details discussed herein should not be understood to limit the invention. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, FIG. 1 is a logical block diagram of a train control system  100  according to the present invention. The system  100  includes a control unit  110 , which typically, but not necessarily, includes a microprocessor. The control unit  110  is connected to a positioning system such as a GPS receiver  120 . The GPS receiver  120  can be of any type, including a differential GPS receiver. Other types of positioning systems, such as inertial navigation systems (INSs) can also be used. The GPS receiver  120  provides position and speed information to the control unit  110 . 
     A database  130 , which contains the locations of all grade crossings in the system (or in the area in which the train is to operate) is also connected to the control unit  110 . In some embodiments, the database  130  can be updated through wireless communication (via wireless transceiver  140 ) or other means to accept changes in grade crossing information. The control unit  110  uses the position information from the GPS receiver  130  as an index into the database  130  to determine the nearest grade crossing being approached by the train. 
     The control unit  110  is also connected to an electrically activated horn  140 . Although a horn  140  is used in the embodiment of FIG. 1, it should be understood that any type of warning device, or combination of warning devices, including visual and audio warning devices, could be used. 
     Referring now to FIG. 2, a flowchart  200  illustrates operation of an automatic warning device activation method according to one embodiment of the present invention. The control unit  110  determines the next grade crossing based on the location of the train as reported by the GPS receiver  120  by indexing the database  130  at step  210 . If the next grade crossing is subject to state regulations at step  220 , the warning device (e.g., horn) is activated in accordance with state regulations at step  230  and the process starts over at step  210 . 
     If the next grade crossing is not subject to state regulations, then the system treats the grade crossing as subject to the aforementioned FRA regulation, 49 C.F.R. § 222. The control unit  110  then determines whether the train is within ¼ mile of the grade crossing at step  240 . If not, step  240  is repeated. When the train is within ¼ mile of the grade crossing at step  240 , the control unit  110  next calculates the estimated time of arrival of the train at the grade crossing, based on the position and speed of the train as reported by the GPS receiver  120 , at step  250 . If the estimated time of arrival is less than 24, seconds, step  250  is repeated using updated speed and position information at step  250 . If the estimated time of arrival is less than 24 seconds at step  260 , the warning device is activated at step  270 . In some embodiments in which the warning device includes a horn, the horn is sounded in a two long, one short, one long sequence. If the control unit determines that the train has not cleared the grade crossing at step  280 , step  270  is repeated. If the grade crossing has been cleared, the process is repeated starting at step  210 . 
     It will be readily understood by those of skill in the art that the aforementioned invention can be practiced as a stand-alone system or may be practiced as part of an automated train control system. The database  130  may be programmed via wireless communications from a dispatcher or central authority, or may be periodically updated by reading data from a tape or flash memory in a manner well known in the art. 
     The embodiment described above has been discussed with reference to grade crossings. It will be readily understood by those of skill in the art that the invention can be used in connection with any location, temporary or permanent, at which it is required or desirable to activate a warning device. One example of such a temporary location is an area of track being worked on by maintenance personnel. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.