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Train Tracking (with occupancy changes) and Dynamic Scheduling

 

Most transit authority office systems track trains on a railway by assigning a unique identifier to the train - such that the progress of a particular train can be observed against it's schedule. Trains are assigned these unique ID's in a number of different formats, however the principal is generally the same. An identifier is used to track the train's progress though the railway, and these ID's are either assigned manually by an operator, automatically based upon a schedule, assigned by the interface of another system, or most often, a combination of all of these.

 

The concept is simple. Once a unique ID is assigned to a train (represented as an occupancy state on an office system), the train ID will stay with the train as it moves through the railway without any further user action. This is accomplished by the sequence of adjacent track occupancies as they change while the physical train progresses through the railway. Though the concept is simple, the reality is a somewhat more complex than might first be imagined. Consider the complexities involved when trains merge together on the same tracks, individual trains separate from the same tracks, or what might occur during the occurrence of "false" occupancies (where an occupancy state changes even though a physical train is not on the track).

 

B&C Transit Consultants, Inc. have considerable experience dealing with all the complexities of train tracking, and have solutions to all such adverse conditions that might occur on a railway in order to maintain the highest possible accuracy.

 

Since yard systems are considerably more complex to track than mainline systems (due to the close proximity of trains, makes, breaks, etc), we will focus on the concepts used in yard systems for the purposes of this discussion.

 Networked Car Tracking (Yard to Central)

Refer to the numbers enclosed within circles in the illustration above: 

 

  1. Track occupancies are sent from the non-vital processor to the Application Terminal Server (ATS). The ATS detects all changes in track occupancies and acts upon them to track trains through the yard. (for a description of ATS, see Networked Office Systems).

  1. CENTRAL main line computers deposit train ID information for tracks entering the Yard into the RDBMS on the Central servers for the yard servers to retrieve when the corresponding yard entrance track becomes occupied.

 

  1. CENTRAL main line computers retrieve yard group number information for tracks “exiting” the Yard from the RDBMS servers in the yard.

 

  1. Based upon changing track occupancies and resulting calculated train movement, the Application Terminal Server updates the Rail Car tables residing on the Yard servers.

 

  1. The ATS queries the yard Rail Car table only upon startup. The ATS queries the Central servers only when yard “entrance” tracks become occupied.

 

  1. As track occupancies change, cars are reassigned to different tracks. The Application Terminal Server places this information into the Indications table for workstation GUI applications and historical playback. Only cars on occupied tracks are sent to the workstations.

 

  1. Workstation GUI applications receive changing status of track occupancies and associated car information.

 

   8.   Reporting tools, Car Information Window, and the workstation TRACKER function query the yard Car table or Central Car table to find a car either in the yard, the mainline, or another yard.

 

  1. Operators at workstations can manually add, modify, or remove cars from tracks. This change request is sent to the ATS. The ATS provides the work for the request and alerts all workstations of the change.

 

 

The specific reasons for setting up communications in this fashion are explained below. 

 

      Placing cars and group numbers in the indications table ensures that all workstations will receive this information simultaneously with train movement, and this information will be readily available during “playback” operations – along with all other indications. 

 

       If workstations were to be allowed to update the yard Car table directly, then, if a user clicks on a track to change the cars for the track, but the train proceeds to the next track before the user finishes the assignments, the workstation could possibly assign the cars and trains in the yard Car table to a track that is no longer actually occupied. 

 

        If the workstations were allowed to make updates directly to the tables, then the Application Terminal Server would have to continuously query these tables to detect user changes, and this would slow down overall processing time throughout the system considerably.

 

Logical relationship of rail cars to trains on a yard track

The best and most reliable method of train tracking is to track the physical location of the rail cars themselves.

 

To accomplish this, B&C Transit office systems go the extra mile. Rail cars are logically grouped as trains and the trains are assigned ID's so they can be displayed and tracked throughout the system.

 

Since a yard track can physically have more than one train (group of cars) on a single track, and even unlinked cars, logical relationships have been devised to ensure that car tracking is performed with a 100% degree of accuracy. This relationship allows trains to merge onto a single track, and then exit that track without disrupting the train ID's that existed on that track prior to the merge.

Take the following example of a merge operation. The illustration is divided into three different views:

 

LOGICAL

 

GRAPHICAL

 

PHYSICAL

 

 

A train with four cars is approaching an occupied track that also contains a four car train. Observe each view to see how our systems manage to track these trains independently, even though they may eventually exist on the same track circuit.

Four car train on TC3 approaching occupied track TC12

Once track TC3 becomes "unoccupied", it "pushes" its rail cars onto the merge track (TC12).

 

 

Track TC12 now contains two separate trains of 4 cars each as noted by the logical grouping.

 

 

The operator could group all the cars into a single 8 car train (based upon transit capability) by selecting the track icon and performing the function.

 

 

Note in the illustration, that if cars are NOT grouped into a single 8 car train, and TC3 again becomes occupied, then only one train (group AB2) will be pulled off.

 

 

To pull off "all" the cars with this occupancy change, the operator would first group all cars on this track into a single train.

Train merges onto track TC12. Two distinct trains now exist on the same track.

 

Certainly there is more to dynamic car tracking than the examples in this section show. We must keep some of the secrets to ourselves for now. But suffice it to say we can handle any situation, regardless of switch positions and occupancy state changes, and can even track over storage tracks that have no occupancy detection! Such an interface allows yard operators to search not only for trains, but for the individual rail cars themselves. This is considerably a more powerful tracking system than any we've seen in the industry.

 

 

Dispatching to Schedule

 

B&C Transit Office Systems allow schedule files, in any predetermined format, to be loaded into the office systems for dispatch to schedule functions and for status and progress reporting. Schedule files generally exist as weekday, Saturday, Sunday, and Holiday schedules. The Office system determines which day of the week the current day is, and uses the appropriate schedule files for dispatching and reporting.

 
 
Send mail to mkirk@bnctransit.com with questions or comments about this web site.
Last modified: 04/07/06