Abstract:
A method and apparatus for determining the real time location of wheeled cars linked together in a train traveling on a fixed track. The method creates a wheel count and a location point for the train by counting the number of wheels on the train in a sequential order as the train passes a first wheel counting station, wherein the wheel counting station is stationary at a fixed location. The wheel count and location point for the train is then recorded in a computer. As the train passes subsequent wheel counting stations positioned along the track, the train is identified by recounting the wheels on the train and matching the number of recounted train wheels to the wheel count. The location point of the train is updated in the computer to correspond to the location of the last wheel counting station and to count the number of wheels on the train. Subsequently, a rail car location in the computer is created, wherein the rail car location corresponds to the last updated location point for the train. Accordingly, the method apparatus use a plurality of wheel counting stations, sensors, and a computer to determine the location of linked cars on a fixed track.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of application Ser. No. 09/235,389, filed Jan. 22, 1999, entitled Automated Railway Crossing, now U.S. Pat. No. 6,241,197, the disclosure of which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a modular communication system that monitors railcar movement along a train line. 
     BACKGROUND OF THE INVENTION 
     Rail is an important method of transporting goods and people to and from populated areas. Rail is often used to ship goods in bulk over long distances in specialized container cars. Due to the variety of different types of goods which can be shipped by rail, a variety of different types of rail cars are often used to carry different types of goods. For example, perishable food items are often transported in refrigerated rail cars, whereas liquified gases are often carried in pressurized liquid container cars. In order to maximize the cost effectiveness of shipping cargo by rail, an individual train may consist of several engines linked to multiple rail cars. Indeed, a train may comprise literally hundreds of different types of cars carrying different types of goods, destined for different destinations. When a train enters a rail yard, several cars may be removed from the train while other cars are added to it, depending on the ultimate destination of the particular rail cars. Hence, the particular composition of a train will change as it moves from rail yard to rail yard. In many cases, a particular cargo item will be placed on a rail car which is assembled into a first train which leaves its departure point in one city. Before that cargo item reaches its ultimate destination in another city, the rail car on which that cargo item rode, may have been part of two or more separate trains. Likewise, the exact composition of a train may vary considerably from rail yard to rail yard as rail cars are removed and additional rail cars are added. 
     Since different rail cars on a train may have different points of departure and different destinations, it becomes vitally important to keep an accurate track of the different cars comprising a train. Traditionally, each rail car has an identification tag which has information concerning that car, including its point of departure, its destination and/or its cargo. To keep track of where particular rail cars are, an operator must first identify each rail car by reading the rail car tags. This can be a time consuming operation. In recent years, rail car tags have been developed which can be read by a wayside computerized optical card reader. In practice, however, since rail cars are being transferred at various customer locations along the track, the composition of the train as it travels from customer location to customer location is very difficult to trace. 
     Keeping track of the location of particular rail cars has also been a problem since rail car tags are generally read when the cars enter and leave a rail yard. Hence, it was only when the rail car was in a rail yard that the precise location of the car could be determined. While automatic wayside rail car tag readers may be used, cost limits their use to a few locations. Customers and/or rail way personnel had no practical method to determine the exact location of particular rail cars when the rail cars were in transit. Since a train may travel literally hundreds of miles from tag reader to tag reader, it is difficult for a rail company to know precisely where any particular shipment may be. As a result, it is very difficult for customers who are having cargo shipped by rail to determine with confidence where their cargo is, and what the expected time of delivery will be for the cargo. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the drawbacks of the prior art by providing a method of monitoring the progress of rail cars linked together in a train. The method comprises the steps of creating a wheel count and a location point for the train by counting the number of wheels on the train in sequential order as the train passes a first wheel counting station having a known location, the location point corresponding the location of the first wheel counting station. The wheel count and location point are then recorded in a computer. The train is then identified as the train passes subsequent wheel counting stations positioned along the track by recounting the wheels on the train and matching the number of recounted train wheels to the wheel count, each of said wheel counting stations having a known location. The location point in the computer is then updated when the train is identified to correspond to the location of the last wheel counting station to count the number of wheels on the train. Then a rail car location is created in the computer, the rail car location corresponding to the last updated location point for the train. 
     The present invention also directed at a system for determining the real time location of wheeled rail cars linked together in a train travelling on a fixed track. The system includes a plurality of wheel counting stations positioned along the track, the wheel counting stations each adapted to accurately count the wheels of the train as the train passes the station to create a wheel count for the train, the wheel count corresponding to the total number of wheels counted by the wheel counting station, each wheel counting station having a known location. The wheel counting stations are each adapted to transmit an information signal to a first computer operatively coupled to the wheel counting stations when the train passes the stations, said information signal including the wheel count for the train and location information corresponding to the location of the wheel counting station generating the wheel count. The first computer is adapted to store the wheel count and location information in a memory module. The first computer is also adapted to identify the train when it passes a wheel counting station by matching the number of wheels counted by said wheel counting station to the wheel count for the train. The first computer is further adapted to generate a location point corresponding to the location of the last wheel counting station to count the number of wheels on the train. Also, the first computer is adapted to create a rail car location corresponding to the location point. 
     The invention is also directed to a system for minimizing the distance between trains travelling on a fixed track, the trains each having a plurality of wheels. The system includes a plurality of wheel counting stations positioned along the track. The wheel counting stations are each adapted to accurately count the wheels of each train as the train passes the station and generate a wheel count for each train corresponding to the number of wheels on the train counted by the wheel counting station, each wheel counting station having a known location. The wheel counting stations are adapted to transmit an information signal to a remote computer operatively coupled to the wheel counting stations when the trains pass the stations, said information signal including the wheel count for each train and location information corresponding to the location of the wheel counting station generating the wheel count. The first computer is adapted to store the wheel count and location information for each train. The first computer is further adapted to identify each train when they pass a wheel counting station by matching the number of wheels counted by said wheel counting station to the wheel count for the respective trains. The first computer is further adapted to generate and store a location point for each train corresponding to the location of the last wheel counting station to count the number of wheels on the train. The wheel counting stations are also adapted to measure the speed and direction of the wheels and record the time the wheels were counted for each train. Each of the wheel counting stations are also adapted to transmit the speed, direction and time for each train to the first computer. The first computer has a computer program adapted to calculate and store the estimated size of each train from the respective wheel counts of each train. The computer program is adapted to calculate a minimum safe stopping distance for each train from the respective size of the trains, the recorded times the trains have passed the same wheel counting stations, and the respective speed and direction of the trains recorded when the trains passed said same counting stations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a rail monitoring system made in accordance with the present invention. 
     FIG. 2 is a schematic view of the rail monitoring system of the present invention as applied to a rail yard. 
     FIG. 3 is a schematic view of a train passing a monitoring station component of the present invention. 
     FIG. 4 is a schematic view of the train shown in FIG. 3 as it passes a series of rail monitoring stations. 
     FIG. 5 is a schematic view of a train dropping off a rail car at a customer location. 
     FIG. 6 is a schematic view of a train picking up and dropping off additional rail cars at another customer location. 
     FIG. 7 is a schematic view of a wheel counting station of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is a system and method for tracking the real time location of rail cars and trains as they proceed along a fixed track. The system tracks the progress of trains along the track by periodically identifying the trains as they pass monitoring stations having known locations. Each train is identified by first creating a wheel profile for the train consisting of a list of the rail cars forming the train and the known number of wheels on the train. The profile for each train is stored in a central computer which is readily accessible by a user through the internet or the world wide web. A plurality of wheel counting stations are positioned along the entire length of the track. Each wheel counting station has a known location and is adapted to accurately count the number of wheels on passing trains and transmit this information to the computer. The computer is pre-loaded with software which is adapted to identify the train passing a particular wheel counting station by matching the number of wheels counted by the wheel counting station to the recorded number of wheels for each train. Since there will be relatively few trains having identical numbers of wheels, it is possible to identify each train by its number of wheels. When the train passing a particular wheel counting station is identified, its location is then known since the location of the wheel counting station is also known. 
     Referring firstly to FIG. 1, a rail way line which incorporates the rail traffic monitoring system of the present invention is shown generally as item  10 . The railway line consists of rail track  12  upon which train  14  travels. Train  14  consists of a plurality of rail cars  16  linked together to form a train. Each of the rail cars ride on top of rail track  12  via metal wheels  18 . It will be appreciated that train  14  can consist of a number of different types of rail cars. The rail monitoring system includes a plurality of wheel monitors  21  positioned along track  12 , a receiver  25 , a tag reader  100  and a remote computer  90 . Monitor  21  consists of a computer unit  20  operatively coupled to a wheel sensor  22 . Wheel sensor  22  is mounted adjacent to track  12  and is adapted and configured to accurately and precisely count the number of wheels  18  which pass by the wheel sensor. Wheel sensor  22  is adapted to transmit information concerning the passage of each wheel to computer  20  which stores that data as a wheel count. Wheel sensor  22  is also adapted and configured to measure the speed and direction of the wheels  18  as they pass the sensor. Information concerning the wheel speed and direction are transmitted from wheel sensor  22  to computer  20  which stores the information pertaining to the speed and direction of the car. Computer  20  also records the time train  14  passed wheel sensor  20 . Computer  20  is configured to communicate with receiver  25  and to transmit the wheel count, speed, and direction information to the receiver. Preferably computer  20  has a radio modem operatively coupled to a radio antenna  24  for transmitting said information; alternatively, computer  20  may send that information via a communication line  27 . Preferably, there will be several wheel monitors  21  operatively coupled to each receiver  25 , with each receiver  25  acting as a receiving and relay station for transmitting the information collected by the wheel monitors to central computer  90 . 
     Each rail car  16  has a rail identification tag  11 . Rail identification tag  11  contains information identifying the rail car and its contents. Each rail car has a unique identification number which identifies the rail car. This identification number, together with information concerning the contents of rail car, are stored in identification tag  11 . The information stored in a rail car identification tag  11  can be read automatically by tag reader  100  as rail cars  16  pass the tag reader. Tag reader  100  is operatively coupled to communication line  102  which is in turn operatively coupled to remote computer  90 . Several automatic tag readers are available on the market from manufacturers such as AEI. 
     Receiver  25  consists of a computer  26  which is operatively coupled to either radio antenna  28  or communications line  29  and is adapted to receive communication signals from computer  20 . The computer  26  receives the wheel count, speed and direction information from computer  20  either via a radio modem which is operatively coupled to radio antenna  28  or through a communications line  29  which is operatively coupled to communications line  27 . The computer  26  is also adapted and configured to transmit this information to a remote computer  90  via a modem which is operatively coupled to communication line  30 . Preferably communication line  30  is a high speed communication line such as a T3, satellite uplink, a fibre optic cable, a high speed long distance radio modem communication line or some other high speed communication system. 
     The information concerning the wheel count, speed and direction of train  14  and the rail car ID numbers are stored by remote computer  90  in memory  91 . Preferably this information is organized in memory  91  in the form of a database which correlates train  14 , individual rail cars  16 , and the cargo that each car carries. Memory  91  also stores the schedule for train  14 , including the location of customer drop-off and pick up facilities. Each train is identified by a particular train identification code which corresponds to the schedule for that train. 
     Train  14  may have specialized rail cars  17  which have communications transmitters  23 . Specialized rail car  17  may be specialized to carry particular types of cargo such as perishable goods or liquified gases. Transmitters  23  are computer based communication transponders which are configured to obtain information concerning the status of specialized car  17 . For example, if specialized car  17  consists of a refrigerated car having its own power generation system, transmitter  23  may be adapted to receive information concerning the temperature of the refrigeration compartment, the status of the refrigeration unit and how much fuel is in the power generation unit. Monitor  21  is adapted to interrogate transmitter  23  via a radio signal sent through antenna  24 . When interrogated by signal from monitor  21 , transmitter  23  then transmits a radio signal containing information concerning the status of rail car  17 . Computer  20  is adapted to receive this radio signal and transmitted to computer  26  via communication line  27  or through a radio transmission through antenna  24 . Receiver  25  is adapted to receive the information concerning the status of car  17  and transmits this information to remote computer  90  through communications line  30 . The software in computer  90  is adapted to integrate this information into computer memory  91 , which may be made available to remote users via the internet. 
     Referring now to FIG. 7, the construction and operation of a typical wheel counting monitor  120  used in the present invention shall be explained. Wheel monitor  120  includes a central processing unit  129  operatively coupled to memory  133 , real time clock  145 , wheel sensing elements  123  and  125  and power source  135 . Sensing elements  123  and  125  are adapted to sense the presence of a train wheel (not shown) when the wheel comes into close proximity to the sensing element. Preferably, sensing elements  123  and  125  comprise eddy current sensors. Suitable eddy current sensors are available on the market. Alternatively, sensing elements  123  and  125  may comprise photo-switches which are adapted to optically sense the presence of a train wheel. When sensing elements  123  and  125  sense the presence of a wheel, they immediately send an electronic signal to central processing unit  129 . 
     Memory  133  will store the software required by the processor to calculate the speed and direction of the train from the electronic signals received by wheel sensing elements  123  and  125 . The distance between sensing elements  123  and  125  is stored in memory  133 , therefore enabling monitor  120  to determine the speed of passing trains by dividing the distance between the sensing elements by the time interval between the signals received from the two sensing elements. Monitor  120  can also calculate the direction the train is travelling by noting which sensing element sends the first electronic sensor. Preferably, sensing elements  125  and  123  are sufficiently precise that they can signal processor  129  with each train wheel that passes, enabling the processor to count the number of wheels passing the sensing elements. The number of wheels counted may be stored in memory  133 , together with the speed and direction of the passing train. Central processing unit  129  may comprise any high speed processor such as a Pentium TM 486 or greater. Central processing unit  129  and memory  133  are mounted on a suitable circuit board. Prefabricated boards having suitable processors and memory as well as additional supporting circuitry, are commercially available. 
     Preferably, central processing unit  129  is operatively coupled to a communications interface  137  which is in turn operatively coupled to wireless modem  132 . Wireless modem  132  comprises a high speed communications radio modem adapted to operate at 19 K baud or higher. Wireless modem  132  has an effective range sufficient to reliably communicate with third processor  134 . Wireless modem  132  is operatively coupled to antenna  138  which is preferably mounted on a tower to increase the effective range of the modem. Alternatively, communications interface  137  may be operatively coupled to a wired modem (not shown), which is in turn connected to a telephone, fibre optic or other suitable communications line. 
     Central processing unit  129 , memory  133 , sensing elements  123  and  125  and wireless modem  132  are all powered by power source  135 . Power source  135  can be a simple rectified transformer coupled to line current. Alternatively, power source  135  can be a battery backed solar energy source. 
     Referring now to FIG. 2, the method of the present invention shall now be discussed in greater detail by way of example. The example starts with the assembly of a train at a rail yard and then follows the train as it travels down the track. Train  40  is assembled from a plurality of rail cars  16  which are coupled together in rail yard  34 . For example, rail cars  42 ,  44 , and  46  may be joined together to be part of train  40 , depending on the instructions given to rail yard personnel. As train  40  passes rail yard exit  41 , tag reader  104  reads tags  11  on each of the cars as they pass the tag reader. The tag information is communicated to remote computer  90  via communication line  106 . In close proximity to tag reader  104  is positioned wheel monitor  48  which counts wheels  18  as train  40  passes. Wheel monitor  48  is operatively coupled to communication line  50  which carries the wheel count information from monitor  48  to remote computer  90 . The wheel count information is also stored in memory  91  and is correlated to the rail car tag information collected by tag reader  104 . Train  40  then moves along track  52  to its final destination. Another train  32  having rail cars  35 ,  36  and  38  can enter rail yard  34 . Wheel monitor  54  counts wheels  18  of each of cars  35 ,  36 , and  38  as the cars pass the wheel monitor. Wheel monitor  54  transmits this wheel count information to remote computer  90  via communication line  56 . This wheel count information is again stored in computer memory  91 . As cars  35 ,  36 , and  38  enter rail yard  34 , their identification tags  11  are read automatically by tag reader  108 . Tag reader  108  transmits this tag information to remote computer  90  via communication line  110 . Again, memory  91  correlates the wheel count information to the tag information for train  32 . 
     Referring now to FIG. 3, as train  40  travels along track  52 , its progress is periodically monitored by monitoring stations positioned along the rail line. For example, as train  40  passes a train monitoring station  58  information concerning the train is read by the monitoring station and transmitted via communications line  64  to remote computer  90 . In this particular example, train  40  consists of locomotive  45 , and cars  42 ,  44 , and  46 . Each of these cars and the locomotive all have particular ID numbers displayed on tags  11 . For this example, locomotive  45  has the identification number L 01 , whereas cars  42 ,  44 , and  46  have ID numbers C 01 , C 02 , and C 03 . As train  40  passes monitoring station  58 , tag reader  60  reads tags  11  as the train passes. At approximately the same time, wheel monitor  62  counts the wheels on train  40  as the train passes. Hence, as train  40  passes monitoring station  58 , wheel counting monitor  62  counts the trains twenty wheels and transmits the wheel count information to remote computer  90 . Tag reader  60  then reads tags  11  which identifies each rail car making up train  40  in sequential order and transmits this identification information to remote computer  90  which stores it in computer memory  91 . The software pre-loaded in memory  91  is adapted to create a wheel count profile for the train by combining the wheel count for the train with the sequential order of the rail cars on the train. Since the number of wheels on each rail car is known, it is possible to adapt the software to specify the wheels corresponding to each of the rail cars in the train. In this particular example, the profile shows that wheels  1  to  8  correspond to locomotive  45  (ID L 01 ), wheels  9  to  12  correspond to car  42 , wheels  13  to  16  correspond to rail car  44  and wheels  17  to  20  correspond to rail car  46 . This wheel count profile is summarized in table 1. 
     
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 ID Number 
                 Wheel position 
               
               
                   
                   
               
             
             
               
                   
                 L01 
                 1-8 
               
               
                   
                 C01 
                  9-12 
               
               
                   
                 C02 
                 13-16 
               
               
                   
                 C03 
                 17-20 
               
               
                   
                   
               
               
                   
                 Number of wheels on train 40 (wheel count) = 20 wheels  
               
             
          
         
       
     
     The software loaded into memory  91  is adapted to organize the wheel profile for the train into a relational database which references each rail car to its corresponding train. The database is also adapted to permit the software to search for particular rail cars by a variety of identifying factors such as identification number, customer name, destination, starting point and any other identifying factor which may be required by users. The software is further adapted to create a location point for the train as soon as the train passes wheel monitor  62 , the location point for the train corresponding to the known location the wheel monitor. The software is adapted to store the location point for the train in the database. Since each rail car is part of the train, the location of each rail car (i.e. the rail car location) will correspond to the location point for the train. As will be explained below, the software is further adapted to update the location point for train  40  as the train passes wheel counting stations along the track. 
     Each train has a schedule summarizing the identification of each of the cars in the train, the route the train is to take and the location of customer drop off and pick up points. It will be appreciated, that as rail cars are added to or removed from the train, the number of wheels on the train will change as the train progresses from customer location to customer location. The train schedule is, in effect, a list of predicted changes in the wheel profile of the train. The software is adapted to use the schedule for each train to generate a list of predicted wheel counts for the train corresponding to the number of wheels on the train at various locations along the track and to match those predicted wheel counts to the actual number of train wheels counted by the wheel counting monitors. In this way, the software can continuously update the database to reflect the last recorded location of the train as the train passes progressive wheel counting monitors. 
     Referring now to FIG. 4, as train  40  continues along track  52  the train will pass a series of wheel counting (monitoring) stations placed along the track. The exact location of each wheel counting station is known and is preferably pre-loaded in computer memory  91 . As train  40  passes wheel counting monitors  72 ,  74 , and  76 , the wheel counting monitors will transmit the time the train passes each monitor, the number of wheels counted at each monitor (the updated wheel count) and the speed and direction of the wheels measured at each wheel monitor. This information is immediately relayed to computer  90  where it is stored in memory  91 . The software loaded into memory  91  is preferably adapted to identify train  40  by its wheel count. Since only a relatively few number of trains will have the exact same number of wheels at any given time, the software loaded in memory  91  can identify train  40  by matching the updated wheel counts to the number of wheels on the train recorded in memory  91 . Hence, when wheel counting monitor  74  reports the passage of a train having an updated wheel count matching the number of wheels on train  40 , the software in memory  91  will identify the train passing monitor  74  as train  40 . The software is preferably further adapted to update the location point for the train to correspond to the location of the wheel monitor which generated the last matching wheel count (in this case monitor  74 ). 
     Preferably, the software in memory  91  is further adapted to calculate a predicted rail car and train location at any given time by adding to the last location point the product of multiplying the last recorded speed of the train by the time interval since the train was last identified. In this way, computer  90  can generate not only the last confirmed position of train  40  (and therefore, the last confirmed position of any rail car on the train) but also the predicted location of the train. This provides accurate information as to the exact real time location of train  40  and, therefore, accurate information on the real time location of any rail car on the train. 
     As train  40  passes monitoring stations  66 ,  68  and  70 , the wheel count profile for the train is verified and the information concerning the train is updated. Since the positions of train monitoring stations  66 ,  68  and  70  are known, the location of car  46  is updated periodically as train  40  progresses down track  52 . Hence a user logging on to computer  90  from computer terminal  96  via the internet  94 , can display information on computer screen  98  relating to the progress of car  46  as the car travels down track  52 . Since the train monitoring stations also measure the speed and direction of the wheels, and therefore the rail car, the database loaded into memory  91  can display for the user the estimated time of arrival of car  46  at the next monitoring station or at the final destination. Hence, the user can have current and accurate information concerning the exact location of any rail car. 
     In the event rail car  46  is inadvertently decoupled from train  40 , the wheel count of the train at the next wheel monitoring station will not correspond to the wheel count information contained in memory  91  of computer  90 . Personnel monitoring the progress of train  40  can then note the discrepancy and inform the train&#39;s conductor that a rail car has been decoupled. Furthermore, since the profile and location point information are periodically updated, the approximate location of the missing rail car can be elucidated and the appropriate action may be taken to collect the missing rail car. 
     Preferably the rail monitoring stations are spaced every five kilometers or so along track  52 . The relatively close spacing of monitoring stations permits very accurate information to be relayed to users as to the progress of train  40  and any particular rail car on that train. Since the method of the present invention uses relatively inexpensive wheel monitors to identify trains, and since it is possible to link several wheel monitors to a relay station via radio modems, the entire system may be relatively inexpensive to construct and maintain. 
     Referring now to FIG. 5, after train  40  passes rail monitoring station  70 , it passes customer facility  84  where it drops off rail car  46 . Train  40  then continues down track  52  where it passes monitoring station  78 . Wheel monitor  80  of monitoring station  78  then counts wheels  18  of train  40  and transmits the updated wheel count to computer  90 . The wheel count profile for train  40  is then updated as summarized in Table 2. 
     
       
         
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 ID Numbers 
                 Wheel Count 
               
               
                   
                   
               
             
             
               
                   
                 L01 
                 1-8 
               
               
                   
                 C01 
                  9-12 
               
               
                   
                 C02 
                 13-16 
               
               
                   
                   
               
               
                   
                 Predicted wheel count for the train at wheel monitor 80 = 16 wheels  
               
               
                   
                 Actual number of wheels counted on the train at monitor 80 = 16 wheels  
               
             
          
         
       
     
     Since the train was scheduled to drop off a car having 4 wheels at customer location  84  located between monitoring stations  70  and  78 , the software loaded into memory  91  calculates the predicted wheel count for the train at monitor  80  (in this case 16 wheels). If the actual wheel count at wheel counting monitor  80  corresponds to the predicted wheel count, then the software confirms that car  46  was dropped off at customer location  84 . A remote user logging on to computer  90  from computer terminal  96  can then verify that car C 03  was dropped off at customer location  84  and that car C 02  is still aboard train  40 . 
     Train monitoring station  78  will have wheel monitor  80 , but may or may not have tag reader  82 . Even if monitoring station  78  does not have tag reader  82 , the monitoring station can update computer  90  on the progress of train  40  as it passes the monitoring station. The software is adapted to identify the train by matching the number of wheels counted at monitor  80  to the predicted wheel count for train  40  as derived from the train schedule. If a second train (not shown) passes monitor  80  before train  40  reaches it, the software will not identify the second train as train  40  since there will most likely be a different number of wheels on the second train. When the software identifies train  40 , it amends the database to update the location point of the train to correspond to the location of the last wheel counting station to count the number of wheels on the train (in this case, monitor  80 ). 
     An alternate method of identifying the train as it passes a monitoring station is to query an identification transponder (item  40 ) on the train. Many trains are equipped with radio transponders which transmit radio signals identifying the train. These transponders are generally located in the locomotive. When triggered, these transponders send out an electromagnetic signal containing an identification sequence particular to that locomotive. Monitoring station  78  communicates with transponder  43  and transmits the identification information received from transponder  43  to remote computer  90 . Wheel monitor  80  then counts the wheels on train  40  and transmits the updated wheel count information to computer  90 . Since memory  91  contains the train identification number as well as the updated wheel count information and the list of drop offs and pick ups for that train, computer  90  can monitor the progress of the train to ensure that it is dropping off and picking up cars as scheduled. 
     Referring now to FIG. 6, as train  40  continues down track  52 , it will drop off rail cars  42  and  44  at another customer location  86  as specified in the schedule. While at customer location  86 , train  40  may pick up rail cars  112 ,  114  and  116 , again according to the schedule for the train. When train  40  passes monitoring station  87 , wheel monitor  88  counts wheels  18  on train  40  and transmits this information to computer  90  which stores the information in memory  91 . Computer  90  then compares the wheel count for train  40  to the predicted wheel counts to ensure that the correct cars have been dropped off and picked up. For example, on the train schedule corresponding to train  40 , cars  42  and  44  (corresponding to car ID #C 01  and C 02 ) were to be dropped off at customer location  86 . Also according to the schedule for train  40 , cars  112 ,  114  and  116  were to picked up at customer location  86 . Since the schedule will specify the type of cars that are being picked up at customer location  86 , computer  90  will be able to calculate that train  40  should have dropped off 8 wheels (corresponding to cars C 01  and C 02 ) and gained 12 wheels (corresponding to cars  112 ,  114 , and  116 ) for a predicted wheel count of 20 wheels. As train  40  passes monitoring station  87 , wheel monitor  88  counts the number of wheels and transmits the latest wheel count information to computer  90  which compares the counted number of wheels to the number of wheels predicted from the schedule. If the latest wheel count matches the predicted number of wheels on the train, then computer  90  verifies that the train is progressing as scheduled. Computer  90  then updates the location point for the train to correspond to the location of the last wheel monitor to count the number of trains on the wheel (in this case, monitoring station  87 ) and can therefore calculate the location point of the rail cars riding in the train. Again a user can verify the location of cars  42  and  44  by using a computer terminal  96  which is operatively coupled via internet  94  to remote computer  90 . If monitoring station  87  also has a tag reader  89 , then the tag reader will read tags  11  on newly configured train  40  and transmit the tag information to computer  90 . Computer  90  then updates the wheel count profile for train  40  in memory  91 . 
     The system of the present invention is also useful in maximizing the train traffic on a track. The maximum train traffic on a track is governed by the average separation between the trains. Decreasing the distance separating trains will increase the number of trains on the track. The distance separating each train is preset to exceed the minimum safe stopping distance of each train. Since the wheel counting system disclosed herein keeps track of the speed and direction of the train as well as the number of wheels on the train and the identity of the rail cars, it is possible for the computer to calculate a minimum safe stopping distance for each train. By calculating a minimum safe distance for each train, the separation between trains can be tailored to maximize the number of trains on the track. 
     Generally speaking, the larger a train is, the more it will weigh, and the longer the stopping distance required. Likewise, the faster a train is travelling, the greater the stopping distance required for the train. Calculating a safe stopping distance for a train is simply a mater of plugging the mass and speed of the train into an equation. Hence, by estimating the weight of the train, the computer can calculate a safe stopping distance for the train from the known speed of the train. The weight of the train can be estimated from the wheel count of the train simply by multiplying the number of wheels on the train by a weight factor. The weight factor can be predetermined to represent the estimated maximum weight of a train per wheel. For example, if we assume the weigh factor to be 5 tons/wheel, the weight of a train having twenty wheels can be estimated to be no more than 100 tons. If the speed of the train is known, then an acceptable stopping distance for the train can be calculated. 
     A more accurate safe stopping distance can be calculated if the identity of the rail cars are known. The identification information for each rail car should include the approximate weight of the rail car. If all of the rail cars on a train are identified, then the computer can calculate a fairly accurate weight for the train by summing all of the weights of the rail cars. The computer can then calculate a more accurate minimum safe stopping distance for the train. 
     With the minimum safe stopping distances for each train on the track calculated, an operator can instruct to various trains to adjust their speeds to minimize the separation between trains. The central computer can be pre-loaded with software adapted to automatically calculate the minimum safe stopping distance for each train from the wheel count, speed, direction and composition of the train. 
     Specific embodiments of the present invention have been disclosed; however, several variations of the disclosed embodiments could be envisioned as within the scope of this invention. It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.