Patent Publication Number: US-6340139-B1

Title: Highway grade crossing vehicle violation detector

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to means and apparatus for detecting a location of a vehicle, and more particularly to detecting the unsafe or illegal presence of a vehicle in a railroad grade crossing. 
     A majority of train-vehicle accidents at grade crossings occur when drivers ignore or do not observe warning systems such as gates, flashing lights, or warning signs. The railroad industry and state transportation authorities regularly engage in construction projects to increase the level of safety as these intersections, particularly drawing on accident statistics as a means of prioritizing potential improvement projects. With the advent of inexpensive monitoring systems that operate over channels on the nation&#39;s cellular telephone infrastructure, a means exists by which data pertaining to crossing violations can be delivered to recipients who would find such information very valuable. Adding an effective means of detecting such an occurrence to a communications device requires a more precise detection device that can withstand wide temperature and environmental extremes faced in such an application while maintaining sharply bounded detection zones. 
     Previous means of accomplishing this task have been hindered by the cost and lack of precision of other detection technologies such as infrared, light beams and photocells, and microwave security intrusion sensors. The accuracy and repeatability of these technologies vary widely over time, temperature, and weather conditions. Ice, snow, rain, and dust can render them inoperative. Buried loops can detect vehicles, but they are costly to install and maintain, and do not detect pedestrian traffic. 
     In addition, it would be desirable if statistics of crossing violations could be accumulated over time for remote grade crossings. If such statistics were known, it may be possible to identify “problem” crossings and to make changes to reduce the occurrence of violations. 
     BRIEF SUMMARY OF THE INVENTION 
     In one embodiment, the present invention is therefore an alarm monitor for a railroad grade crossing, the grade crossing having an island activation relay that is activated in response to an approaching train, the alarm monitor including a micropower impulse radar (MIR) responsive to pedestrians and motor vehicles in a prohibited area of the crossing island during activations of the island activation relay; and a processor configured to generate a warning signal when the MIR detects a pedestrian or a motor vehicle in the prohibited area during an activation of the island activation relay. 
     It will be seen that embodiments of the present invention provide a cost-effective system for detecting and reporting instances of vehicles and pedestrians violating crossing warning systems. Using these embodiments, railroad industry and state transportation authorities can learn of elevated risk situations without waiting to compile accident statistics. With such information, better decisions can be made with respect to increased enforcement, implementation of alternate warning systems, or other remedies to reduce the likelihood of accidents. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified block diagram of one embodiment of an alarm monitor of the present invention. 
     FIG. 2 is a simplified map of a grade crossing having gate arms that drop to warn approaching vehicular and/or pedestrian traffic of an approaching train, showing one technique for mounting an embodiment of an alarm system of the present invention. 
     FIG. 3 is a simplified map of a grade crossing similar to that of FIG. 2, but without gate arms, showing another technique for mounting an embodiment of an alarm system of the present invention. 
     FIG. 4 is a simplified map of a grade crossing having a four quadrant gate, showing still another technique for mounting an embodiment of an alarm system of the present invention. 
     FIG. 5 is a simplified map of a grade crossing similar to that of FIG. 2, but having cantilevers crossing over a portion of a highway near prohibited edge boundaries. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is a simplified block diagram of one embodiment of an alarm monitor  10  of the present invention. Alarm monitor  10  comprises at least one Micropower Impulse Radar (MIR)  12  that is responsive to pedestrians or vehicles in a prohibited area of a railroad grade crossing (not shown), the prohibited area being a region of the grade crossing that is dangerous for a pedestrian or vehicle to occupy during approach and passage of a train. A MIR is a device that produces a short, low power microwave impulse and that has the capability of detecting reflections from objects within a limited distance range. Such radars have the capability of detecting pedestrians and/or motor vehicles at a range of no more than about 30 feet (9 meters) due to power limitations of the radar unit itself. The range limitation is desired to reduce susceptibility to spurious signals outside of prohibited region. The limitation is also used to advantage in some embodiments to avoid reflections from the train itself, as it crosses the grade, and to avoid spurious indications due to animals that may enter a grade crossing from directions other than the highway. One example of a suitable MIR  12  is an RRF24 Rangefinder, available from TEM Innovations, Pleasanton, Calif., which has a maximum range of about 20 meters, but which can be adjusted to detect in a more limited range. Another suitable MIR is described in U.S. Pat. 5,805,110, issued Sept. 8, 1998 to Thomas E. McEwan. 
     MIRs  12  are also configured to transmit detection data relating to pedestrians and vehicles in the prohibited area to a nearby processor  14 . Transmission is via a hardwired connection  16 , via a radio link  18 , or via already existing field wiring  20 . Although several transmission modes are shown in FIG. 1, only one is required in any particular embodiment. In one embodiment, a spread spectrum modulator  22 , for example, an I NTELLON ® SSC P200 modulator/demodulator (available from Intellon, Inc., Ocala, Fla.) is utilized to modulate the detection signal before transmission over connection  16 , radio link  18 , or field wiring  20 . In this embodiment, a spread spectrum demodulator  24  (for example, also an I NTELLON ® SSC P200 modulator/demodulator) is used to demodulate transmissions of detection data at processor  14 . (Only field wiring link  20  is shown equipped with modulator  22  and demodulator  24  in FIG. 1.) 
     Various installations of embodiments of alarm monitor  10  in a grade crossing  26  are illustrated in FIGS. 2 through 5. Referring to FIG. 2, grade crossing  26  has a signal bungalow  28  containing equipment that activates gate arms  30 ,  32  when a train (not shown) on either of tracks  34  or  36  activates an island activation relay (not shown). This activation causes gate arms  30 ,  32  to drop, blocking oncoming traffic in both directions on highway  38 . However, as a safety feature, each gate arm  30 ,  32  on a typical grade crossing  26  only extend across a portion of highway  38 . This safety feature allows a vehicle that has already entered a prohibited area  40  of grade crossing  26  to continue through on their side of the road. However, the presence of this safety feature also allows an impatient pedestrian or vehicle driver to circumvent the signaling and protection afforded by gate arms  30 ,  32  by changing traffic lanes and going around the gate arms. Needless to say, this practice is dangerous. 
     In the embodiment of FIG. 2, MIRs  12 A and  12 B are mounted on ends of gate arms  30 ,  32 . MIRs  12 A and  12 B are positioned on these arms so that, when gate arms  30  and  32  are lowered, MIRs  12 A and  12 B are directed to detect objects in a narrow region around boundaries  42 ,  44  of prohibited area  40  on highway  38  that are not blocked by gate arms  30 ,  32 . MIRs  12 A and  12 B are energized when the island activation relay (not shown) is activated, and thus become responsive to pedestrians and vehicles improperly crossing boundaries  42  and  44  when gate arms  30  and  32  are lowered. 
     MIRs  12 A and  12 B provide an advantageous configuration in that they have a combination of a relatively limited range (e.g., no more than about 6 to 9 meters, or no more than about 20 to 30 feet) and a relatively precise zone of coverage (i.e., a relatively precise angular coverage). Thus, alarm system  10  defines rather sharply defined detection zones  46 ,  48  that are more resistant to spurious alarms and more sensitive to actual intrusions into prohibited area  40  from highway  38  than systems using standard microwave security intrusion sensors. Furthermore, the accuracy and repeatability using MIRs  12 A and  12 B is greater than that obtainable using standard microwave security intrusion sensors, or infrared and light beam/photocell sensors. Unlike these sensors, MIRs are resistant to ice, snow, rain, and dust that can render these other sensors inoperative. Also, unlike buried loops, which are difficult to install and maintain, pedestrian (and bicycle) traffic is readily detected. 
     When intrusion into either zone  46  or  48  is detected, a detection data signal is transmitted to processor  14  inside signal bungalow  28 . The transmission path is not shown in FIG.  2 . However, as discussed in connection with FIG. 1, transmission is via a hardwired link, a radio link, or via field wires (not shown in FIG. 2, but shown in FIG. 1) that supply lights and gates  50 ,  52  with their electrical energy. In some embodiments, to ensure a metal path when transmission is via field wires, MIRs  12 A and  12 B contain additional circuitry to synchronize transmission of detection data with the presence of a flashing voltage on the field wires. Transmission via spread spectrum modulation, with repetitions of signals from MIRs  12 A and  12 B enable processor  14  in one embodiment to receive asynchronous transmissions from MIRs  12 A and  12 B. 
     In one embodiment, processor  14  makes a determination that grade crossing  26  is active. This determination is made either directly in response to the activation of the island activation relay by an approaching train (not shown), or indirectly in response to such activation, such as by sensing activity of a flashing relay (not shown). When this determination is made, and during such times that the grade crossing  26  is signaling that the train is approaching or crossing grade crossing  26 , when a signal indicating an intrusion is received from either MIR  12 A or  12 B, processor  14  generates a warning signal. In one embodiment, the generation of a warning signal is conditioned upon the activation of the island activation relay. Also in one embodiment, the warning signal and is used to control transmission of a signal intended for reception at a location remote from grade crossing  26  to alert officials (and/or the train engineer) that a hazardous condition has just occurred. Also, the warning signal is used to increment a counter (not shown separately in FIG. 2) to keep track of the occurrences of such hazardous conditions. In one embodiment, the warning signal and the counter are both internal to processor  14  and are implemented using software or firmware. In this manner, processor  14  can be accessed at a later time to determine how many times hazardous attempts have been made to cross grade crossing  26 , and a decision made to further action taken to reduce such hazardous crossing attempts based upon the stored count. 
     In one embodiment, the violation detection capabilities of outer MIRs  12 A and  12 B are augmented by one or more additional central MIRs  12 C,  12 D positioned and directed to be responsive to pedestrians and vehicles only within a central portion  54  of prohibited area  40 . Processor  14  receives detection data from the one or more central MIRs  12 C,  12 D and is configured to present its alarm signal only if a central MIR  12 C and/or  12 D detects the presence of a pedestrian or vehicle after an outer MIR  12 A or  12 B has detected the pedestrian or vehicle. This further requirement for an alarm indication further reduces false alarms that may occur when a vehicle or a pedestrian is detected only when leaving grade crossing  26 , or in the event a portion of vehicle or pedestrian grazes a detection zone  46  or  48  but does not cross either track  34  or  36 . In one embodiment, such events are noted and recorded by processor  14 , but are given a lower priority and/or are counted separately. Although central MIRs are illustrated in FIG. 2 in conjunction with an embodiment in which outer MIRs are mounted on gate arms, central MIRs are also used in other embodiments having outer MIRs having different mountings. 
     FIG. 3 is an illustration of an embodiment of alarm system  10  mounted on a grade crossing  26  that does not use gates or gate arms. Instead, grade crossing  26  signals the approach of a train by activating flashing lights  56  mounted on masts  58 A,  58 B,  58 C and  58 D that are located near corners of prohibited area  40 . In this embodiment, MIRs  12 F,  12 G,  12 H and  12 J are mounted on masts  58 A,  58 B,  58 C, and  58 D, respectively, and are configured to detect pedestrians and vehicles in detection regions  60 ,  62 ,  64  and  66 . Thus, MIRs  12 F,  12 G,  12 H and  12 J detect intrusions that occur by pedestrians and vehicles that cross a boundary of prohibited area  40  in a traffic lane nearby a corresponding mast  58 A,  58 B,  58 C and  58 D. As used herein, being “mounted on a mast” is not intended to exclude being mounted on one of the flashing lights  56  mounted on a mast. 
     FIG. 4 is an illustration of an embodiment of alarm system mounted on a grade crossing  26  in a manner similar to that shown in FIG.  3 . The example of FIG. 4 differs in that grade crossing  26  is provided with a four quadrant gate having four gate arms  30 A,  30 B,  32 A, and  32 B, where gate arms  30 A and  32 A are entrance gate arms and gate arms  30 B and  32 B are exit gate arms. Interference with detection regions  60 ,  62 ,  64  and  66  of MIRs  12 F,  12 G,  12 H and  12 J by gate arms  30 A,  30 B,  32 A, and  32 B is minimized because MIRs  12 F,  12 G,  12 H and  12 J are configured to have limited range and well-defined and delimited detection coverage. 
     The embodiment illustrated in FIG. 5 is similar to that shown in FIG. 2, except that in FIG. 5, MIRs  12 K and  12 L are mounted on cantilevers  68  and  70  that cross above a portion of highway  38  near prohibited area  40  boundaries  42 ,  44 , respectively. Also, MIRs  12 K and  12 L are configured to have broad, but limited distance, detection regions  72  and  74  directed towards highway  38  from cantilevers  68  and  70 , respectively. 
     It will thus be seen that embodiments of the present invention provide a cost-effective system for detecting and reporting instances of vehicles and pedestrians violating crossing warning systems. Using these embodiments, railroad industry and state transportation authorities can learn of elevated risk situations without waiting to compile accident statistics. With such information, better decisions can be made with respect to increased enforcement, implementation of alternate warning systems, or other remedies to reduce the likelihood of accidents. 
     The use of MIR technology by the various embodiments renders the alarm monitor impervious to rain, snow and dust, and allows it to operate in a very precise manner, maintaining very sharply defined detection zones over a wide range of environmental extremes. In embodiments in which the island activation relay is also monitored, the alarm monitor makes accurate determinations that the warning system is activated and that an object is present where it should not be. Advantageously, in some embodiments, signals from the MIR are superimposed on the power conductors that supply the lights and gates with their electrical energy or transmitted via radio, so that the requirement for additional wiring that might be exposed to the elements or have to be buried is minimized. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.