Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
' CA 02835657 2013-11-29
..
85549-112D2
TITLE: Railroad switchyard management process and related
infrastructure
FIELD OF THE INVENTION
The invention relates to a process for managing operations in
a railroad switchyard. The invention also encompasses a
technological platform and individual components thereof to
implement the process.
BACKGROUND OF THE INVENTION
A railroad network normally contains one or more switchyards
in which cars are routed from tracks leading from a departure
point to tracks going to a destination point.
A typical
switchyard has four main components, namely receiving tracks, a
car switching mechanism, a set of classification tracks and a set
of departure tracks. Incoming trains deliver cars in the receiving
tracks.
The cars are processed by the switching mechanism that
routes individual cars to respective classification tracks.
Two types of switching mechanisms are in use today. The
first one is a hump switch. Switch yards that use a hump switch
are referred to as hump yards. A hump switch yard uses a hump
over which a car is pushed by a locomotive. At the top of the
hump, the car is allowed to roll on the other side of the hump
under the effect of gravity. Retarders keep the car from reaching
excessive speeds. The hump tracks on which the car rolls down the
hump connect with the classification tracks.
A track switch
establishes a temporary connection between the hump tracks and a
selected one of the classification tracks such that the car can
1
= CA 02835657 2013-11-29
85549-112D2
roll in the classification tracks.
A departure train is
constituted when the requisite number of cars has been placed in a
set of classification tracks. When the departure train leaves the
switchyard, the set of classification tracks becomes available for
building a new departure train.
The second type of switch mechanism is a flat switch. The
principle is generally the same as a hump yard except that instead
of using gravity to direct cars to selected classification tracks,
a locomotive is used to push the car from the receiving tracks to
the selected set of classification tracks.
In order to increase the efficiency of switching operations,
railway companies have developed the concept of car blocking.
Under this concept, a block of cars, hence the name "blocking",
may be logically switched as a unit in a switch yard. A block is
established on a basis of certain properties shared by the cars
belonging to the block.
For instance, cars that have a common
destination point on their route can be blocked together.
A
"block" is therefore a logical entity that helps making switching
decisions. For reference, it should be noted that, generally, two
types of blocks exist. There is the so called "yard block" and a
"train block". For clarity, the term "block" alone in the present
specification encompasses either a yard block or a train block.
The principle of blocking, either yard blocking or train
blocking, increases the efficiency with which cars are processed
at switch yards. However, it also brings constraints.
Very
often, a train block must be assembled from cars that arrive on
different incoming trains. The train block will be complete and
2
CA 02835657 2016-05-06
available for departure only when all the cars that make up the
train block have arrived at the switch yard. If one or more of
the cars are delayed, the train block cannot be completed and the
entire departing train that pulls this train block may leave
without the train block. Such occurrence may create a cascading
effect throughout entire segments of the railroad network and have
significant financial repercussions for the railroad operator.
Specifically, it is not uncommon for an operator to guarantee car
arrival times to customers and delays incur financial penalties
that may be significant.
Against this background, it can be seen that a need exists in
the industry to develop more refined processes to manage
operations in a switch yard such as to increase the efficiency
with which cars are switched.
SUMMARY OF THE INVENTION
As embodied and broadly described herein, the invention also
provides a system for computing car switching solutions in a
railway switch yard that has a switch and a plurality of
classification tracks, the railway switch yard holding a
plurality of empty cars yet to be switched by the switch, said
system comprising:
a. input means for receiving data specifying a particular
empty car to include in a departure train to be built
by the railway switch yard;
b. a processing entity including a CPU and a machine
readable storage encoded with software, the software
being configured for computing car switching solutions
3
CA 02835657 2016-05-06
*
to assemble the departure train, the car switching
solutions including substituting an empty car from the
plurality of empty cars to the particular empty car;
c. output means for releasing data conveying the car
switching solutions.
As embodied and broadly described herein, the invention also
provides a method for computing car switching solutions in a
railway switch yard that has a switch and a plurality of
classification tracks, the switch yard holding a plurality of
empty cars yet to be switched by the switch, said method
comprising:
a. receiving input data specifying a particular empty car
to be included in a departure train to be built by the
railway switch yard;
b. computing with a computer car switching solutions to
assemble the departure train, the car switching
solutions being such as to assemble the departure train
including substituting in the departure train an empty
car from the plurality of empty cars to the particular
empty car;
c. releasing output data conveying the car switching
solutions.
As embodied and broadly described herein, the invention also
provides a method for assembling a train block in a railway
switchyard that includes a section for holding a plurality of
railcars including empty railcars and non-empty railcars to be
classified into a plurality of classification tracks, the method
including:
4
CA 02835657 2016-05-06
a. electronically receiving data from a source, the data
identifying a train block to be assembled at the
railway switchyard, the train block having a plurality
of non-empty railcars and one particular empty railcar;
b. selecting by using a computer among the plurality of
classification tracks a classification track on which
the train block is to be assembled;
c. performing a switching operation to direct non-empty
railcars that belong to the train block from the
plurality of railcars into the selected classification
track;
d. selecting by using the computer an empty railcar among
the plurality of railcars, other than the particular
empty railcar to be substituted to the particular empty
railcar;
e. switching the selected empty railcar into the selected
classification track;
f. whereby the train block is assembled into the selected
classification track with the selected empty railcar in
lieu of the particular empty railcar.
As embodied and broadly described herein, the invention also
provides a method for assembling a departure train in a railway
switch yard, the railway switch yard including receiving tracks,
the receiving tracks holding a plurality of railcars including
empty railcars and non-empty railcars, the method comprising;
a. electronically receiving by a computer data
describing the departure train to be assembled,
the
data identifying at least one empty railcar to be
included into the departure train;
5
CA 02835657 2016-05-06
b. identifying by using the computer an empty railcar
among the plurality of railcars in the receiving tracks
to be substituted to the empty railcar identified by
the data;
c. switching railcars from the receiving tracks to
assemble the departure train, including the empty
railcar identified by the computer as a substitution
for the empty railcar identified in the data;
d. generating by the computer a message conveying
that the departure train has been assembled with an
empty railcar other than the empty railcar identified
in the data.
BRIEF DESCRIPTION OF THE DRAWINGS
A detailed description of examples of implementation of the
present invention is provided hereinbelow with reference to the
following drawings, in which:
Figure 1 is a schematical illustration of a hump switch
yard;
Figure 2 is a high level block diagram of a prior art
computer based switch yard management system;
Figure 3 is a high level block diagram of a computer based
switch yard management system according to a non-limiting example
of implementation of the invention;
Figure 4 is a more detailed block diagram of the system
shown in Figure 3;
6
CA 02835657 2016-05-06
Figure 5 is a graph illustrating the process of allocating
two separate train blocks of cars to a single classification
track;
Figure 6 is a flowchart illustrating an iterative process
for computing car switching solutions according to a non-limiting
example of implementation of the invention;
Figures 7 and 8 are more detailed flow charts of the general
process illustrated in Figure 6;
Figure 9 is a flowchart illustrating a logical process for
selecting an occupied classification track in which to switch a
car;
Figure 10 is a flowchart illustrating a logical process for
determining if a car should be rehumped based on small train
block size;
Figure 11 is a flowchart illustrating a logical process for
determining if a car should be rehumped based on arrival rate;
Figure 12 is a flowchart illustrating a logical process for
selecting a classification track to receive only a portion of a
train block;
Figures 13 and 14 illustrate logical processes for
performing empty car substitution.
In the drawings, embodiments of the invention are
7
CA 02835657 2016-05-06
illustrated by way of example. It is to be expressly understood
that the description and drawings are only for purposes of
illustration and as an aid to understanding, and are not intended
to be a definition of the limits of the invention.
DETAILED DESCRIPTION
Figure 1 is an illustration of a hump switching yard in
which the management process of the invention can be implemented.
The hump switching yard 10 has four main components namely
receiving tracks 12, a hump 14, classification tracks 16 and
departure tracks 17.
The receiving tracks 12 include railway
sections in which an incoming train delivers cars to be switched.
The receiving tracks 12 lead to the hump 14. The hump 14
includes a set of tracks 20 that lead to the hump crest 18 that
is the highest elevation of the hump 14. Cars are pushed by a
locomotive on the tracks 20 up to the hump crest 18 at which
point the car rolls down the hump 14 by gravity toward the set of
classification tracks 16.
The car passes through retarders 22
that will reduce its speed allowing it to gently coast in anyone
of the selected classification tracks 16.
A track switch 24,
located downstream the retarders 22 temporarily connects the hump
track 12 to a selected one of the classification tracks 16 such
as to direct the car to the desired classification track 16.
The receiving tracks 12, therefore, form a switching queue
in which cars that are delivered to the switching yard 10 await
to be switched.
8
CA 02835657 2016-05-06
The classification tracks 16 lead to the departure tracks
17.
Specifically, the classification tracks are arranged into
groups where each group leads to a departure track 17. The hump
switch yard 10 shown in the drawings includes 10 classification
tracks organized into two groups of five tracks. Each group of
five tracks connects to the departure track 17.
Generally, the classification tracks 16 are used to assemble
train blocks. Train blocks are pulled out of the classification
tracks into the departure tracks 17 where the actual departure
train is built. The departure tracks 17 allow assembling trains
having more cars than a single classification track can hold.
When a complete train (short train) is assembled into a single
classification track 16, the departure train leaves that track
directly by passing through the departure track 17.
It should be appreciated that Figure 1 is a very simplified
illustration of a hump switch yard in that the number of tracks
shown has been significantly reduced for clarity purposes. An
average size hump yard typically contains many more
classification tracks than what is shown in Figure 1.
For
example it would not be uncommon for a switchyard to have 80 or
more classification tracks organized into physical groups of
tracks, where each group connects to a departure track.
In
addition, there will normally be a larger number of departure
tracks 17 than what appears on the drawing.
The hump switch yard 10 also includes a reswitching track
that allows to "recirculate" cars from a position downstream the
switch 24 to a position upstream the switch 24.
In a typical
9
CA 02835657 2016-05-06
,
hump switch yard, such as the yard 10, the reswitching track is
called "rehump track". The rehump track is shown at 26 in Figure
1. The rehump track 26 originates downstream the track switch 24
and lead to the hump tracks 20 at the base of the hump 20. The
purpose of the rehump tracks 26 is to provide a buffering
mechanism where one or more cars can be temporarily put in
storage without blocking the flow of other cars through the hump
switch yard 10. For instance, situations may arise where one or
more cars in the receiving tracks 12 cannot be switched in any
one of the classification tracks 16.
This may be due, for
example, to the lack of space availability in the classification
tracks 16. It is common practice for a hump switch yard 10 to
periodically hump the cars in the rehump tracks 26.
Such
rehumping involves pushing the cars over the hump 20 such that
they can be switched to a selected classification track 16. If a
car cannot be routed to any one of the classification tracks 16,
it is put back in the rehump tracks 26 for a new humping cycle.
The following description of a non-limiting example of
implementation of a switch yard management process will be done
in connection with a hump switch yard 10 of the type described
earlier.
However, it should be expressly noted that the
principles of the invention apply equally well to a flat switch
yard. Accordingly, the invention should not be limited to a hump
switch yard but encompasses a flat switch yard as well. A flat
switch yard operates generally in the same way as described
earlier in that incoming trains deliver cars at the input side of
the flat switch yard, a switching device routes the individual
cars to classification tracks to assemble departure trains in
departure tracks.
CA 02835657 2016-05-06
Figure 2 illustrates a block diagram of a prior art control
system 28 for use in managing the operations of a hump switch
yard 10. Specifically, the control system 28 includes two main
components, namely the Service Reliability System (SRS) component
30 and the Hump Process Control System (HPCS) 32.
The SRS
component 30 is in essence a railway traffic management system
that keeps track of the rolling stock inventory throughout the
network. It is used to manage the flow of railway traffic over a
complete railway network or a portion thereof. The SRS component
30 is a computer based system that reflects the railway
operations by showing information on trains, schedules, waybills,
trip plans and train delays. The SRS component 30 has a number
of sub-systems that are integrated to one another. Some of the
sub-components are briefly described below:
= Waybill - a computer file that provides details and
instructions on the movement of cars. Cars and units cannot
move without a waybill;
= Service Scheduling - the service scheduling sub-component is
based on a trip plan that specifies the events a shipment
must follow from origin to destination.
A trip plan
identifies the train connections for each car and provides a
destination Estimated Time of Arrival (ETA). The
service
scheduling sub-component continuously monitors the movement
of each shipment and compares its progress to the trip plan.
If the service scheduling determines that a shipment will
not meet the established requirements, it triggers alarms;
11
CA 02835657 2016-05-06
= Yard Operating Plan/Daily Operating Plan (YOP/DOP) - the YOP
sub-component defines how assets (crews, cars, locomotives
and tracks) are allocated to support yard related
activities. The DOP is derived from the YOP and contains
instructions for industrial assignments;
= Yard, Industry and Train (YIT) - the YIT sub-component
allows users to report train and car movements such as train
arrivals and departures, yard switches, exchange of cars
with other railroads, and the placing and pulling of cars at
a customer sidings.
= Intermodal - this sub-component includes functions for
gating-in, gating-out, assigning, ramping, de-ramping as
well as maintaining inventories of Intermodal equipment.
The SRS component 30 includes a processing function that is
illustrated as a single block, but it can be implemented also in
a distributed fashion.
It should be expressly noted that the SRS component 30 is
merely an example of a railway traffic management system and
other railway traffic management systems can be used without
departing from the scope of the invention.
The HPCS component 32 operates the track switch in the hump
switch yard 10. Essentially, the HPCS component 32 is a car
switch control system that determines on the basis of inputs the
position of the track switch 24 such that a car, or a series of
cars over the hump, will be directed to the desired
12
CA 02835657 2016-05-06
classification track 16. Broadly stated, the HPCS component 32
has two main goals, namely:
= Deliver the cars to the correct classification track 16;
= Insure that the cars will arrive in the classification track
16 fast enough to reach the cars already in the track but
slow enough for a safe coupling (or reach the far end of the
track if it is empty);
As in the case with the SRS component 30, the HPCS component
32 is illustrated as a single block but it can be implemented in
a distributed fashion.
It should be expressly noted that the HPCS component 32 is
merely an example of a car switch control system and other car
switch control systems can be used without departing from the
scope of the invention.
As shown by Figure 2, a human intervention 34 is required to
interface the SRS component 30 and the HPCS component 32.
Specifically, the SRS component identifies the trains that are
scheduled to arrive at the hump switch yard 10 and the trains
that are scheduled to depart the hump switch yard 10. On the
basis of this information, a hump list is manually produced. The
hump list determines in which classification track the various
cars will go. The hump list is then loaded into the HPCS
component 32. The HPCS component 32 performs the switching as the
cars are humped according to the specific switching instructions
in the hump list.
13
ak 02835657 2016-05-06
In order to simplify the car switching logic, it is
customary to assign classification tracks 16 to destinations.
For instance there is the "Edmonton" classification track, the
"Montreal" classification track, etc. Cars that go to Edmonton
are switched to the Edmonton classification track, cars that go
to Montreal are switched to the Montreal track, etc.
Note the communication link 35 between the HPCS component 32
and the SRS component 30. This link 35 illustrates the exchange
of data between the two components, for instance the HPCS
component 32 notifying the SRS component 30 of events or
conditions occurring in the hump switch yard 10.
Figure 3 is a block diagram of control system 44 for use in
managing the operations of the hump switch yard 10, according to
a non-limiting example of implementation of the invention. The
control system 44 includes three main components, two of which
are shared with the prior art control system 28 described
earlier.
Specifically, the control system 44 includes the SRS
component 30, the HPCS component 32 and a Dynamic Track
Allocation (DTA) controller 46.
The DTA controller 46 is
responsible for allocation of cars to the classification tracks
16.
Figure 4 is a block diagram of the DTA controller 46 showing
the relationships with the SRS component 30 and the HPCS
component 32.
The DTA controller 46 has a computing platform
including a processor 47 that communicates with a machine
readable storage unit 49, commonly referred to as "memory" over a
14
CA 02835657 2016-05-06
data bus. Inputs and outputs (I/O interface) 51 allow the DTA
controller 46 to receive and send data to the SRS component 30
and the HPCS controller 32, via the SRS component 30.
In
addition, the I/O 51 communicates with a user interface 53 that
allows the DTA controller 46 to communicate information to the
yard master and receive commands or other inputs from the yard
master. In essence, the user interface 53 shows the yard master
the switching solutions that the DTA controller 46 is developing.
Those switching solutions can be implemented either
automatically, i.e. pending an input from the yard master that
stops the process, the proposed switching solutions are executed,
or they may require explicit confirmation from the yard master.
For instance, unless the yard master inputs at the user interface
53 a command to explicitly implement or authorize the switching
solution presented by the DTA controller 46 on the user interface
53, no action is taken by the system.
Note that, while the diagram at Figure 4 depicts the DTA
controller 46 as a single unit, it can also have a distributed
architecture without departing from the scope of the invention.
The functionality of the DTA controller 46 is software
defined. In other words, the logic that determines how cars are
to be switched is implemented by executing software by the
processor 47. The software in the form of program code is stored
in the memory 49. The software reads data inputs received from
the SRS component 30, and from the user interface 53.
On the
basis of those inputs, the DTA controller 46 generates outputs to
the user interface 53. The output to the user interface 53 is
intended to display information to inform the yard master on the
CA 02835657 2016-05-06
switching solutions the DTA controller 46 has reached.
Optionally, an output may also be directed to the HPCS component
32, which contains switching commands that determine the
positions of the track switch 24 and effectively implement the
switching solutions developed by the DTA controller 46.
It should be expressly noted that the present invention does
not absolutely require the generation of control signals to the
HPCS controller 32. While this option is considered
advantageous, variants can be envisaged where there is, in fact,
no direct command given by the DTA controller 46 to the HPCS
component 32. For instance, the DTA controller 46 can compute
switching solutions that are presented to the yard master or
another operator and manually implemented or manually authorized.
As indicated earlier, the DTA controller 46 determines how
the hump switch yard 10 will allocate cars in the classification
tracks 16. This is done on the basis of various parameters that
will be discussed below. In addition, the DTA controller 46 is
provided with some degree of flexibility in determining the make
up of train blocks such as, for example, collapse train blocks
when it is not appropriate to continue assembling them or
splitting big train blocks into smaller ones in order to make
better use of existing space in classification tracks 16.
Another feature of the DTA controller 46 logic is allowing a
dynamic car re-distribution. This is particularly suitable for
empty cars that need to be delivered by the railroad operator to
the customer or car owner.
In the example illustrated in Figure 4, the DTA controller
16
CA 02835657 2016-05-06
46 logically resides between the SRS component 30 and the HPCS
component 32.
As such, the DTA controller 46 receives
information from the SRS component 30 about:
= Incoming trains (trains to be received in the hump switch
yard 10), in particular:
o Identification of the train (Train ID)
o The Expected Time of Arrival (ETA);
o Point of origin;
o Destination;
o Identification of the train blocks that make up the
train;
o The number of cars in each train block;
o The identification of each car (car ID);
o The destination of the car;
o The route of the car;
o If the car carries cargo, the type of cargo; and
o If the car is empty the customer that has requested the
car to be moved.
m Departure trains (trains the switch yard 10 is expected to
assemble);
o Identification of the train (Train ID)
o The Expected Time of Departure (ETD);
o Identification of the train blocks that make up the
train;
o The number of cars in each train block;
o The identification of each car (car ID);
o The destination of the car;
o The route of the car;
17
CA 02835657 2016-05-06
o If the car carries cargo, the type of cargo; and
o If the car is empty, the customer that has requested the
car to be moved.
In order to make classification track assignments to
individual cars, the DTA controller 46 creates representations in
the memory 49 of the rolling stock that transits through the hump
switch yard 10 by using hierarchal objects.
Generally, three
types of objects exist:
= A train object. A train object is associated with each train
(arrival train or departure train) and it has properties
such as:
o A train identifier (train ID);
o Expected time of arrival (ETA);
o Origin;
o Destination;
o Route; and
o Identification of train blocks that make up the train.
= A train block object. A train block object is associated
with a block of cars and has the following properties:
o A train block identifier (train block ID);
o Number of cars making up the train block;
o Identity of the cars making up the train block;
o Destination of the train block; and
o Route of the train block from the origin to the
destination.
= A yard block object. A yard block object is associated with
18
CA 02835657 2016-05-06
a block of cars and has the following properties:
o A yard block identifier (yard block ID);
o Number of cars making up the yard block;
o Identity of the cars making up the yard block;
o Origin of the yard block;
o Destination of the yard block; and
o Route of the yard block from the origin to the
destination.
= Car objects. A car object is associated with a single car
and has the following properties:
o Car identifier (car ID);
o Car owner;
o If car carries cargo the type of cargo;
o If car is empty the customer identifier that has
requested the car to be moved;
o Origin;
o Destination; and
o Route between origin and destination.
Normally, train objects that represent incoming trains will
cease to exist when the train arrives at the hump switch yard 10
since the train is dismantled. An exception to this is a
situation where the incoming train transits through the hump
switch yard 10 in which case it remains intact. Departing trains
are represented by train objects that begin their existence at
the hump switch yard 10, having been assembled from cars that
originate from one or more dismantled incoming trains. Incoming
train block objects may cease to exist if the train block is
disassembled and the individual cars are used to make up other
19
CA 02835657 2016-05-06
train block objects. For example, a train block arriving at the
hump switch yard 10 may contain cars having different
destinations. For the sake of this example, say that half of the
cars need to be delivered to city A while the other half to city
B.
In such case, the train block is disassembled and the cars
that go to city A are switched to form, alone or in combination
with other cars from a different train, a new train block that
will travel to city A. The cars directed to city B are switched
in a similar manner. In this situation, two new train blocks are
created at the hump switch yard 10, from one or more incoming
train blocks.
Another possibility is for train blocks to be
modified, instead of ceasing to exist or beginning to exist. A
train block can be modified by augmenting the train block, such
as by adding to it one or more cars or diminished by removing
from it one or more cars.
Finally, a train block may remain
unchanged such as when it simply transits through the hump switch
yard 10. In such case, the train block is physically dismantled
into individual cars but the switching operation is conducted
such as to reassemble the original train block. Alternatively,
the train block can be routed directly to the departure tracks 17
such as to circumvent the switch 24.
As far as individual car objects, they remain unchanged as
they transit through the hump switch yard 10.
The DTA controller 46 receives from the SRS component 30
data that describes the incoming trains so that the DTA
controller 46 can determine the details of the rolling stock to
be processed. The DTA controller 46 also receives information on
the departure trains that the hump switch yard 10 is expected to
CA 02835657 2016-05-06
assemble.
In a specific example of implementation, the DTA controller
46 receives form the SRS component 30 the following information:
= The trains scheduled to arrive to the hump switch yard 10.
The SRS component 30 simply provides the identity of the
train (the train ID);
= The trains that the SRS system expects the hump switch yard
to make. The SRS component simply provides the identity of
the train (train ID).
Once the DTA controller 46 is made aware of incoming trains
and the requirement to build departure trains, the train ID
information allows the DTA controller 46 to determine all the
necessary information down to the individual car.
More
particularly, the train ID allows determining the properties of
the train object and the properties of the train block objects
derived via the train object and the properties of the car
objects derived via the train block objects. This data will then
allow the DTA controller 46 to compute switching solutions.
It should be expressly noted that the above description of
the manner in which information is provided to the DTA controller
46 is strictly an example and should not be constructed in any
limiting manner. Many different ways to deliver information to
the DTA controller 46 exist that allow characterizing the
incoming trains and the departing trains without departing from
the scope of the invention.
21
CA 02835657 2016-05-06
The various functions and features of the DTA controller 46
according to a non-limiting example of implementation will be
described below in conjunction with the process flowchart in
Figures 6 and 7. The flowcharts include a decision tree that
allows the DTA controller 46 to find car switching solutions
based on specific cases. It is to be expressly noted that the
following description is provided only as an example of the
operation of the DTA controller 46 and should not be used in a
manner to limit the scope of the present invention.
Generally speaking, the DTA controller 46 implements an
iterative process that periodically computes car switching
solutions. Those solutions are of temporary nature in the sense
that they are re-computed at each iteration cycle. The switching
solution is frozen in time when the car is committed for
switching. A car that is being pushed over the hump up to the
hump crest 18 is considered committed for switching. Generally,
a car is "committed for switching" when it is close enough to the
switch 24 such that the condition of the hump switch yard 10, in
other words the parameters that determine or influence the
switching solution computed by the DTA controller 46 are unlikely
to change significantly until the actual switching event occurs.
In other words, the latest switching solution in existence when
the car has reached a position in the hump switch yard 10 where
it is "committed for switching" is likely to remain valid until
the car is actually switched since the events and conditions in
the hump switch yard 10 are unlikely to change in an appreciable
manner during the time frame the car transits from the position
"committed for switching" to the switch 24.
22
CA 02835657 2016-05-06
_
The flowchart on Figure 6 illustrates generally the
iteration cycle. The process enters the decision block 600 where
the
DT A controller 46 determines if the car is committed for
switching.
In the affirmative, the previous solution (the
flowchart assumes that a previous solution has been computed) is
maintained. In such case, this solution can be presented to the
yard master of the hump switch yard 10 as being the final
solution.
If the car is not yet committed for switching, the process
continues to step 602 which computes a switching solution which
is either an updated solution or a first solution for this car.
The solution is stored by the DTA controller 46 and will be used
as a final solution if, during the next iteration cycle, the car
is found to be committed for switching. The process then loops
back to decision step 600 and it is thus continuously repeated.
When the switching solution computation step 602 is invoked,
it will process information to select a classification track 16
for each car or block of cars to be humped. Cars are humped in a
given sequence which typically is the sequence in which they
arrive at the hump switch yard 10.
In general, the track
assignment logic that is implemented by the switching solution
computation step 602 has the following characteristics. It is to
be expressly noted that the characteristics discussed below are
not to be considered limiting as they may change without
departing from the scope of the invention.
In particular, a
system that omits a particular characteristic, uses an altered
characteristic or implements a new characteristic should not be
23
CA 02835657 2016-05-06
considered outside the scope of the invention:
1. Expected switch time in computing switching decisions.
The switching solution computation step 602 uses as a
basis for finding a switching solution for a given car,
the expected switch time for that car.
This roughly
represents the time at which the switching solution
computation step 602 expects the car to be switched.
The switching solution will vary with the events and
conditions of the hump switch yard 10 at the expected
switch time. For example, if the expected switch time
is prior to the time the train is scheduled to depart,
then the switching solution will attempt putting the
car in a classification track such that it can be made
part of the train. On the other
hand, if the switch
time is after the departure time of the train, then it
will be plain that different options need to be
considered since that particular train is no longer
available.
The expected switch time is an approximation that takes
into account one or more factors, as it will be
discussed later in connection with a specific example.
2. Dynamic classification track assignment
Switching solution computation step 602 dynamically
assigns classification tracks to train blocks.
By
"dynamic" is meant that the classification tracks are
not constrained to certain destinations or trip plans.
In other words, at some point a classification track
24
CA 02835657 2016-05-06
may be assigned to a train block that goes to
destination A and sometime after the train block is
completed or pulled, the same classification track is
assigned to a train block that goes to destination B.
A consequence of the dynamic classification track
assignment is that a classification track may contain
two or more blocks having different destinations, in
other words, they are associated with different
departure trains.
In this example, the train blocks
are in order of their time of departure. The train
block farther from the hump 14 departs before or at the
same time as the train block closer to the hump 14.
Figure 5 shows this characteristic in greater detail.
The graph shows a single classification track having a
total of 50 cars capacity and the number of cars that
are assigned to the classification tracks at different
times. Initially, only cars that belong to train block
A are being assigned to the classification tracks.
Train block A is closed at 9:30.
The closure occurs
either because the train block is complete (all the
cars that originally form part of the train block have
arrived on time and are delivered to the classification
track) or closed prematurely by the DTA controller 46.
At about 9:30, cars from train block B are delivered to
the classification tracks. At 12:30, train block A is
pulled out of the classification tracks and only cars
from train block B remain. This example illustrates a
situation where cars that belong to different train
blocks simultaneously reside in the same set of
classification tracks. By adequately controlling when
CA 02835657 2016-05-06
the first train block (the one farthest from the hump
14) closes and the respective pull times of the train
blocks (the train block farthest from the hump 14 is
pulled at an earlier time than the train block closest
to the hump 14), the process can be adequately managed
without creating a conflict such that a car or a train
block in the classification tracks is prevented from
being pulled out by a car or a train block of cars
having a latter pull time.
In the above example, train blocks A and B are part of
a different train.
3. Car arrival time considerations
When determining if available space exists in a given
classification track, the DTA controller 46 will take
into account the arrival times (ETA) of the various
cars in the hump switch yard 10.
4. Pull time considerations
When determining if available space exists in a given
classification track, the DTA controller 46 will take
into account the time at which one or more of the cars
that are presently switched in the classification track
or scheduled to be switched therein will be pulled to
make up space.
5. Multiple classification track assignment modes.
Optionally, the DTA controller 46 has the capability to
accept static assignments in connection with one or
26
CA 02835657 2016-05-06
more of the classification tracks 16.
A static
assignment can be maintained permanently or semi-
permanently and it associates the classification track
16 with a departure train having a given destination.
Such static assignments, if used, would normally be
programmed in the DTA controller 46 in a manner to
allow the switching solution computation step 602 to
take this factor into account when computing switching
solutions. The static assignments can be specified to
the DTA controller 46 via the user interface 53 by the
yard master. For example, the yard master of the hump
switch yard 10 may decide that one or more specific
classification tracks will be dedicated for the next 12
hours to cars on the train going to Toronto.
Via
suitable inputs on the user interface 53, the track
identifier(s) is entered and the destination associated
with that track(s) as well or any other suitable
parameter.
When the switching solution computation
step 602 sees a car to be switched that is directed to
a destination other than Toronto, it automatically
discounts the statically assigned classification
track(s).
On the other hand, should a car present
itself that goes on the Toronto train, then the
switching solution computation step 602 will consider
the statically assigned classification track(s) for
that car. The system can be designed to handle static
assignments in a rigid manner such as for instance,
direct cars that go to a destination to which one or
more classification tracks 16 are statically assigned
only to those classification tracks. Another option is
27
CA 02835657 2016-05-06
to use some degree of flexibility in that the static
classification tracks are considered first and if no
space is available, then the cars are allowed to use a
classification track having a dynamic assignment. The
static assignment can be removed in the same fashion as
it was applied, namely through the user interface 53.
The DTA controller 46 holds in its machine readable
storage media a representation of the status of each
classification track 16. This may be
in the form of
any suitable machine readable file stored in the memory
49 (shown at Figure 4).
The file contains the
identifiers of the various classification tracks and a
reference for each classification track as to whether
it is to be used for dynamic assignment or for a static
assignment. When used for a static assignment the file
may also specify certain characteristics such as the
destination the classification track is to be assigned
to, and any other parameter that may be useful.
Another such parameter is the time frame during which
the static assignment is maintained. In such instance,
the yard master enters the end points of the time frame
during which the static assignment is to be maintained
along with any other suitable parameters.
The end
points would normally be the beginning of the time
frame and the end of the time frame. When the time
frame expires, the DTA controller 46 may automatically
switch the classification track 16 to the dynamic
assignment mode, may issue an alert to the yard master
or do both, in other words automatically switch the
28
ak 02835657 2016-05-06
assignment mode and issue a notification such that the
yard master is made aware of the event.
When the yard master changes classification track
assignments via the user interface 53, the changes are
reflected in the file such that during execution of the
switching solution computation step 602, the logic will
be made aware of the correct assignment of each
classification track 16.
Finally, note that assignments can be specified via the
user interface 53 on the basis of classification track
groups instead of being done on a single track basis.
For instance, referring back to Figure 1, the yard
master may simply specify the assignment of an entire
five classification track group.
6. Classification track grouping. This notion can be
implemented in hump switch yards 10 where the
classification tracks are physically arranged into
groups, as shown for example in Figure 1.
The logic
implemented by the DTA controller 46 is designed such
that a departure train that is to be assembled will be
assigned a most preferred group of classification
tracks 16 and a second most preferred group of
classification tracks 16.
In other words, the cars
that go in the train will be preferably put in the
classification tracks of the most preferred group. If
there is no space in the most preferred group, the
second most preferred group will be considered.
29
CA 02835657 2016-05-06
Optionally, a third most preferred group can also be
used such as to provide classification track space when
the second most preferred group is full.
The notion of a preferred group avoids scattering the
train blocks for a given departure train all over the
classification tracks.
The logic of establishing a
preferred classification track group is to try placing
as many of the train blocks as possible that belong to
the same train in the fewest possible classification
tracks that are physically close to one another. This
simplifies the train block pulling operation by
comparison to a situation where the train blocks are
scattered over many classification tracks that may be
physically remote from one another.
Preferably, the most preferred set of classification
tracks and the second most preferred set of
classification tracks are physically close to one
another such as to simplify the train block pulling
operations. The hump switch yard 10 shown in Figure 1
illustrates two groups of classification tracks and one
of those could be designated as a most preferred while
the other as the second most preferred. Thus, the most
preferred group and the second most preferred group are
immediately adjacent to one another.
The same logic
can also be followed in connection with the third most
preferred group, in that it can be selected such that
it is close to the most preferred and second most
preferred group and preferably immediately adjacent
CA 02835657 2016-05-06
thereto.
It is important to appreciate that the notion of
preferred groups is not restricted to switch yards,
either hump yards or flat yards that have physical
groups of the type shown in Figure 1. Even when the
classification tracks 16 are not physically grouped,
they can still be logically associated into groups. In
such case, groups can be defined by assigning two or
more adjacent classification tracks to a group, either
most preferred, second most preferred, etc.
Generally, groups of classification tracks are
associated with departure trains.
Once a preferred
group has been established, either a physical group or
a logical group, that group is maintained until all the
cars scheduled to depart have been delivered in the
classification tracks. After that, the association
between the classification track groups and the train
is dissolved, in other words groups can be assigned to
a new train to be built.
It should be noted that the classification track groups
do not need to be completely empty of cars before being
assigned to a new train. The
assignment process is
essentially a logical step and a re-assignment can
occur as long as there is space in the group to receive
cars for a new train. The two following situations can
arise:
31
CA 02835657 2016-05-06
o The group is closed to cars that belong to a new
train as long as no more cars that belong to the
current train are scheduled to arrive in the
group. Once all cars have arrived, the group of
classification tracks can begin receiving cars
associated with the new train.
o The group is open to cars from a new train as long
as there is space for the cars on any one of the
classification tracks that make up the group.
This implies that cars for the current train can
still be received in any other classification
track of the group.
Consider for example
classification track group made up of 10 tracks.
Track 9 holds a train block of cars that is
complete. The other tracks 1-8 and 10 hold train
blocks that are still incomplete.
The entire
group can now be assigned to a new train since
cars for the new train can be placed in track 9,
while cars for the current train are still
arriving in the other classification tracks of the
group.
In this example, the group is assigned
during a certain time period to two different
trains.
The DTA controller 46 holds in its machine readable
storage media a representation of the different
classification track groups, specifically, identifying
which classification tracks belong to which group and
which departure train is currently assigned to which
classification track group. In the case of a physical
32
ak 02835657 2016-05-06
grouping of the type shown in Figure 1, the
identification of the classification tracks with
relation to the groups will likely be the same as the
physical layout and unlikely to change over time.
However, in instances where no physical groupings
exist, the number and identity of the classification
tracks that make up the groups can dynamically change.
The assignment of a given classification track group
(most preferred, second most preferred, third most
preferred, etc.) can be done manually by the yard
master. This operation is effected via the user
interface 53 or can also be done automatically
7. Non-preferred classification track groups.
In selecting which classification track groups to
assign to a departure train as most preferred, second
most preferred, third most preferred etc, there is a
possibility, as discussed in the previous example, to
co-assign the same group of classification tracks to
different trains. In such, case consideration is given
to the relationship between the departure times of the
trains. Classification track groups will not be co-
assigned to trains that depart at times that are close
to one another in order to avoid a potential congestion
on the tracks. Such congestion is likely to arise if
train blocks for different trains are pulled at about
the same time from the same group of classification
tracks.
8.Rehumping for Fall time.
33
CA 02835657 2016-05-06
Cars to be switched to classification tracks may be
sent to the rehump tracks 26 when the departure time of
the train block to which they belong is far away. This
avoids a situation where a few cars may train block a
classification track for a long time period necessary
for all the other cars that belong to the train block
to arrive. In this case the buffering function of the
rehump tracks 26 can be put to use. The decision to
temporarily put cars on the rehump tracks takes into
account the following factors, individually or in
combination with one another:
a. The pull time of the train block. For example if
the train block is to be pulled many hours away,
it is a good candidate for rehumping;
b. The size of the train block. If the train
block
is small, say a few cars, it is possible to allow
all the cars that belong to the train block to
accumulate in the rehump tracks 26. Then the cars
of the entire train block are humped and placed in
the appropriate set of classification tracks;
c. The rate at which the cars of a given train block
arrive. Even if the train block is large and may
not be contained entirely in the rehump tracks, at
least some of the cars that arrive first can be
held temporarily in the rehump tracks until space
is available in any set of classification tracks.
At this point, the cars stored in the rehump
tracks can be humped in the selected set of
classification tracks and the remaining cars that
make up the train block are directed to the
34
CA 02835657 2016-05-06
selected set of classification tracks.
9.Rehumping for arrival rate.
Cars to be switched to classification tracks may be
sent to the rehump tracks 26 when they arrive at a very
slow rate. This could occur in connection with a given
train block and where the first few cars of the train
block arrive very slowly.
Those cars can then be
directed to the rehump tracks and held there until the
rate of arrival of the cars for that train block
increases, at which point the cars are switched into
classification tracks.
10.Preemptive closure of a train block.
If a train block is kept open for a long time period,
cars that belong to other train blocks may have to be
sent to the rehump tracks.
Rehumping cars consumes
resources which translates into additional operational
costs.
When a large number of cars may need to be
rehumped, it may make more sense to close the train
block and thus open space on the classification tracks.
When a train block is prematurely closed, the cars
arriving post closure that were intended for the closed
train block need to be handled somehow. For instance,
the late cars can be assembled into a new train block.
11.Empty car substitution.
Empty cars are associated with a trip plan as any other
railway car.
To improve the overall car switching
process at the hump yard 10, an empty car (a car that
CA 02835657 2016-05-06
does not carry cargo and is directed to a location to
pick up a shipment) substitution can be implemented
where a given empty car that is currently available for
switching can be substituted for another empty car that
may be late or unavailable for switching. In addition
to the physical car substitution, the records in the
SRS component 30 are updated to indicate that the first
car (the car that is available) has now taken the place
of the second car (the unavailable car) in the trip
plan of the second car.
The exemplary characteristics outlined above will be better
understood with relation to the following specific examples. It
should be expressly noted that characteristics are provided as
examples and should not be interpreted as being essential to the
invention in any way.
Figure 7 is a high level flowchart of the logic that is
implemented by the DTA controller 46 to switch cars, in
particular the step 602 shown at Figure 6.
The decision tree
represented by the flowchart is followed sequentially.
If at
anyone of the steps a switching solution is found, the car is
switched and the process terminates. If no solution is found at
a particular step, the process continues to the next step.
The process starts at 900. At that decision step, the DTA
controller 46 determines if the car is on "pull back". A car on
"pull back" is a car that is currently in position to be pushed
over the hump 14 (or being in position at the hump 14); therefore
it is committed for switching. Accordingly, if the decision step
36
CA 02835657 2016-05-06
900 is answered in the affirmative, any previous switching
solution computed for this car by the DTA controller 46 is
presented as final solution over the user interface 53 (step
901). If this assessment is answered in the negative, the
process continues at step 902 that determines if the yard block
to which the car is assigned exists. This is effected by looking
at the data made available to the DTA controller 46 from the SRS
component. This data includes information about the yard blocks
in the hump switch yard 10. If no yard block exists for the car,
in other words, the decisions step 902 is answered in the
negative, the car is sent to rehump at step 904. Once in the
rehump tracks, the car will be periodically rehumped and the
above described processing is done again. If at this time a yard
block for the car is found, then the process would branch to
decision step 906.
Decision step 906 determines if the yard block to which the
car is assigned is a static train block. A static train block is
a train block that is associated with a static classification
track. As discussed earlier, a static classification track is
one that may be assigned to cars or train blocks associated with
a departure train going to a predetermined destination.
Accordingly, if the decision step 906 is answered in the
affirmative, the switching solution is determined by consulting
the representation of the classification tracks in the DTA
controller 46. As previously indicated, this representation
provides information on the statically assigned classification
tracks and details about such assignment, in particular the
destination of the blocks put on those classification tracks.
37
CA 02835657 2016-05-06
As discussed earlier, a static classification assignment can
be done via the user interface 53.
If no static classification track 16 has been assigned for
the car, the process continues to step 910 that queries if a
train block exists for the car.
This determination takes into
account the expected switch time of the car.
If an outbound
train cannot be found that carries the train block, then it is
not possible to perform a dynamic track assignment. The car is
therefore directed to a rehump track 24 (step 912).
The computation of the expected switch time for a given car
is an approximation of the time at which the car is expected to
be available for switching.
Several factors can be used in
making this determination, for example:
a. The number of cars that are presently in the hump
switch yard 10 and that are yet to be switched;
b. The rate or arrival of cars in the switch yard;
c. The rate at which cars are switched;
d. Resources available to prepare the cars for switching.
Factor (a) and factor (b) allow determining, at any given
time, how many cars will be in the queue awaiting switching.
Recall that this information is readily available to the DTA
controller 46 from the SRS component 30.
Factor (c) can be a
rate computed on the basis of the operations in the hump switch
yard 10 that occurred in the past couple of hours. For example,
a car switching rate can be computed on the basis of the number
of cars switched in a given time frame, say the last two hours. A
car switching rate can also be computed theoretically by taking
38
CA 02835657 2016-05-06
into account resources available (factor d) in the switch yard to
perform the operations necessary to prepare the cars for
switching.
One such operation is the mechanical inspection of
the cars.
One such resource is the number of crews that can
perform the preparation for switching, namely the mechanical
inspection.
By considering the average number of cars that a
crew can mechanically inspect, it is possible to compute the rate
at which cars can be made available for switching.
Another
possibility is to take into account the rate computed on the
basis of switching activities that have occurred in the past
previous hours and adjust it to take into account variation in
the number of crews, for instance increase the predicted rate if
the number of crews increases or decrease the rate if fewer crews
will be available.
The DTA controller 46 can, on the basis of the above
factors, determine for a given car the number of cars that
precede it in the humping queue.
Then, on the basis of the
switching rate, an expected switching time for the car can be
computed.
Note that the expected switching time for the car can remain
static or can be periodically updated, such as at each iteration
cycle where a new switching solution is computed.
A static
expected switching time is a time that once computed is re-used
at every iteration cycle.
In contrast, the expected switching
time can be re-computed periodically as the car moves up through
the queue of cars that are to be switched.
In this fashion, a
more precise approximation can be obtained. The period at which
the expected switching time is re-computed can vary.
One
39
CA 02835657 2016-05-06
possibility is to do it at every iteration cycle at which a
switching solution is computed.
At decision block 914 the process determines if there is an
existing classification track for the train block to which the
car belongs. This query will be answered in the affirmative if
the car is not the first car of a train block. In other words, a
classification track has already been assigned to the train
block.
On the other hand, if the car is the first car of the
train block, then the query will be answered in the negative. If
this query is answered in the affirmative, in other words the car
is not the first car in the train block and a classification
track 16 has already been assigned to this train block, then the
process continues to step 916 shown at Figure 8.
Step 916
determines if the car will in fact fit the classification track
assigned to the train block. As it will be described below, in
principle, there should be enough space on the classification
track 16 assigned to the train block since when the first car of
the train block is switched, the switching solution that
determines which classification track will receive the car, not
only looks for space for that particular car, but also for space
for cars that belong to the train block and that will be
subsequently switched. This will be described later. So while in
principle space should be available, the step 916 still tests for
available space to take into account some special factors. For
instance, there may be situations when more than one
classification track may have been assigned to the train block in
which case the process will determine which classification track
is the best candidate for receiving the car. In such case, the
DTA controller 46 will determine the space available in each
CA 02835657 2016-05-06
assigned classification track 16. For the sake of this example,
assume that two classification tracks 16 have been assigned to
the train block. If not enough space is available in one of the
classification tracks 16 and space is available in the other
classification track 16, the DTA controller 46 will compute a
switching solution directing the car to the classification track
16 having the requisite space. On the other hand, if space is
available in both classification tracks 16, the DTA controller 46
will compute the best fit, in other words it will choose as a
solution the classification track 16 that will leave the least
amount of free space when the car is switched to it.
When the step 916 is executed, the classification track 16
that is tested for available space is retrieved from the memory
of the DTA controller 46. In other words, when a classification
track is assigned to the first car of a train block, the
relationship between the train block and the classification track
is stored in the memory of the DTA controller 46.
When
subsequent cars for that train block arrive and are to be
switched, the DTA controller consults this information to
determine which classification track 16 has been assigned to the
train block and will then test for available space there.
If the decision block 916 is answered in the negative, in
other words no space is available for the car in the
classification track(s) assigned to the train block, then the
processing continues with an overflow logic thread that aims to
find a place for the car on another classification track. The
logic overflow process is shown by block 917.
This logic is
generally similar to the process starting at step 922 and ending
41
CA 02835657 2016-05-06
at step 940.
Those steps will be described in greater detail
later.
If decision block 916 is answered in the affirmative, the
process continues with decision block 919 which determines which
departure train the car will be directed to.
Step 919 is an
option that is useful in circumstances when the car has an
expected switching time close to the pull time of the block. In
other words, it may not be fully known at the time the switching
solution is computed if the car can make the classification track
before the pull time of the block. By default, the logic of the
DTA controller 46 is designed such as to try fitting the car on
the earliest departure train.
So, the logic will compute
switching solutions that put the car in a train block having a
departure time close or slightly before the expected pull time
(the extent of what constitutes "close" or "slightly before" is
programmed in the DTA controller 46 and can be in its simplest
for predetermined time periods).
In some cases, the pull time
may be delayed and the car will in fact make the current train.
Similarly, the actual switch time of the car can occur slightly
before the expected switch time in which case the car will also
be able to make the current train.
In short, as long as the expected switching time is close
enough to the pull time of the current block the DTA controller
46 will compute switching solutions (step 921) that put the car
with a train block scheduled to depart shortly. Only when the
spread between the expected switching time and the pull time
exceeds a threshold or the current block is actually pulled or
for some other reason it becomes obvious that the car cannot make
42
CA 02835657 2016-05-06
the train scheduled to depart shortly, then a different switching
solution is computed (step 923) that puts the car in a train
block with a later train.
The label in Figure 8 "same day
train?" assumes that a departure train leaves every day. Hence,
if the car does not make the current train, it will be put at
step 923 on the next day train.
Referring back to Figure 7, if decision step 914 is answered
in the negative, in other words no classification track has been
yet assigned to the car because this is the first car of a train
block, than the processing branches toward a series of steps that
will first determine if it is suitable to buffer this car instead
of immediately switching it. The buffering process, identified
by the reference numeral 927 includes a first decision step 931.
That decision step assesses the desirability of temporarily
putting the car, and perhaps the following cars that belong to
the same train block, in the rehump tracks 26. Generally, it is
desirable to limit as much as possible the amount of time cars
from a train block reside on the classification tracks 16 since
the space that is occupied by the cars cannot be used for any
other purpose. This problem may arise when the cars that make up
a train block progressively arrive at the hump switch yard 10
over a long time period.
For instance, when a first car is
delivered, a switching decision is made and space is reserved for
the entire train block on the classification tracks 16.
That
space, therefore, cannot be used for other purposes until the
last car of the train block arrives which may be many hours away.
A possible approach is to use the rehump tracks 24 as a temporary
buffer and thus free space on the classification tracks 16. This
option can be implemented when certain conditions are met. Train
block size is one of those conditions.
It is desirable to put
43
CA 02835657 2016-05-06
the car in the rehump tracks 24 when the overall size of the
train block is small. If the determination at step 931 indicated
that the size of the train block to which the car belongs is
small, among other conditions discussed below, the DTA controller
46 will compute a switching solution according to which the car
is directed to the rehump tracks 26. Figure 10 is a flowchart of
the process steps that take place under step 931.
The process starts at step 800. At step 802, the Number of
Cars Remaining for the Next departing Train (NCRNT) for a given
train block is computed. The NCRNT is the number of cars for the
train block that have an expected switching time before the
scheduled pull time of the train block. NCRNT takes into account
cars that are presently in the hump switch yard 10 and also cars
that have not yet arrived but have an ETA such that their
expected switching time will still occur before the train block
pull time.
The DTA controller 46 receives information on the
various parameters necessary to compute NCRNT from the SRS
component 30, such as information on the identity of the train
block and its characteristics, as well as the ETA of the cars
that make up the train block. The DTA controller 46 can compute
the expected switching time for each car as described earlier
and, on the basis of the expected pull time of the train block
that is also available or derived from information in the SRS
component 30, the NCRNT value is computed.
At decision step 804, the DTA controller 46 determines
whether a car will be switched to classification tracks 16 or to
the rehump tracks 26.
The decision is based on the computed
value NCRNT and the pull time of the train block from the
classification track 16.
In the specific example of
44
CA 02835657 2016-05-06
implementation, if NCRNT is relatively small, less than 5 cars
and the pull time of the train block is more than 7 hours away,
then a switching solution is computed to put the car in the
rehump tracks 26 (step 806).
Otherwise, the DTA controller 46
proceeds to step 933 in Figure 7.
The specific parameters in
this example should not be interpreted in a limiting manner since
those parameters can widely change without departing form the
scope of the invention.
Specifically, for instance, the NCRNT
parameter can be increased to more than 5 cars when the rehump
tracks 26 have a lot of space and can accommodate a significant
number of cars.
The period of 7 hours can also be altered
without departing from the scope of the invention.
Decision step 933 tests for another condition that may
result in the car being sent to the rehump tracks 26.
This
condition is the rate of arrival of cars at the switch 24. If
the rate is low, i.e. the cars making up the train block will
have respective expected switching times spread over a long time
period, then it is advantageous to temporarily place the car on
the rehump tracks before switching the car in any one of the sets
of classification tracks 16.
The flowchart of Figure 11
illustrates this process.
The process starts at step 1100. At step 1102, the rate of
arrival of cars for the train block is computed. This rate is
established by determining the number of cars that will be
present in the hump switch yard 10 over a predetermined time
period, say the next 5 hours. The number of cars is the sum of
the cars presently in the hump switch yard 10 and those that are
scheduled to arrive within the predetermined time period.
As
with the previous example, this information is made available to
CA 02835657 2016-05-06
,
the DTA controller 46 from the SRS component 30. Decision step
1104 determines if the rate of car arrival is above or below a
threshold. For example, the threshold may be five cars. So, if
the rate is five cars or more in the next five hours, step 933 is
answered in the negative. Otherwise, if the rate is less than
five cars in the next five hours, then a switching solution to
rehump the car is issued (step 1108).
It will be appreciated
that the specific values provided are merely examples and they
can widely vary without departing from the scope of this
invention.
Note that the rate of arrival factor may also be refined by
computing the expected switching times of the cars making up the
train block instead of looking only at the number of cars of the
train block presently in the hump switch yard 10 and the ETA of
the cars that have not yet arrived.
Assuming now that the decision step 933 is answered in the
negative, in other words the conditions that would trigger a
rehumping solution have not been met, the process continues with
decision step 920.
In most cases, when the processing reaches
this step, the car for which a switching solution is being
computed is the first car for a train block.
Generally, the
computations for finding a solution are more complex than in the
case when subsequent cars are switched since the DTA controller
46 is not only looking for space for the first car but is also
reserving space for the subsequent cars of the train block.
Step 920 first looks for an empty classification track in
the preferred group.
When several empty classification tracks
46
CA 02835657 2016-05-06
are available within the preferred group, one option is to
randomly choose one.
This is suitable when all the empty
classification tracks have the same capacity, in other words each
empty classification track can accommodate the same number of
cars. When empty classification tracks with different capacities
are available, an option is to choose the one that best fits the
train block. In this context, "best fit" means a classification
track that will contain the least amount of empty space when the
entire train block will be delivered in the classification track.
The "best fit" computation can be done for each empty
classification track by subtracting the train block size from the
track capacity. This computation can be made in terms of number
of cars or in terms of cumulative car length to take into account
cars having different lengths. If an empty classification track
is found at step 920, a switching solution is computed (step
935).
Otherwise, the process continues at decision step 922
which is the same as decision step 920 except that the search for
an empty classification track is done in the second most
preferred classification track group. Again, if no solution is
found at step 922, step 924 performs the same operation, this
time looking for an empty classification track in the third most
preferred classification track group.
If anyone of the decision blocks 920, 922 or 924 is answered
in the affirmative, in other words an empty track is found for
the train block, the DTA controller will make an entry in the
records in its memory 49 such as to associate the selected
classification track with the particular train block. Such
association is made by marking the selected empty classification
track as "opened" and marking all the other classification tracks
47
CA 02835657 2016-05-06
as "closed" as far as that train block is concerned.
As
indicated above, this is done by writing the appropriate data in
the computer files or records that the DTA controller 46
processes to perform its management functions. Accordingly, when
switching solutions are computed for any subsequent cars of that
train block, all classification tracks that are marked "closed"
are disregarded and the search for switching options is
constrained to the "opened" classification track.
Referring back to step 914, which is looking for an existing
track for a train block, the "closed" or "opened" status of the
classification track allows the DTA controller 46 to identify the
correct classification track that is to receive the car.
Once a classification track is marked as "opened" in
connection with a certain train block, that classification track
is also marked as "closed" for any other train block.
This
ensures that the classification track will receive only cars for
the relevant train block.
The "open" status of a classification track is negated when
the switching solution for the last car of the train block has
been computed. In other words, the train block is now complete.
Similarly, the "closed" status of the classification track with
regard to any other train block is also negated, thus allowing
cars of another train block to be directed to the classification
track.
If no switching solutions have been found at anyone of the
steps 920, 922 and 924, indicating that no empty tracks for the
48
CA 02835657 2016-05-06
train block are available in anyone of the preferred
classification groups, the DTA controller 46 continues with
decision step 926 that tries to find space for the train block in
an already occupied track.
The process will try to find space first in the most
preferred group, then the second most preferred group, then the
third most preferred group before considering other options. The
decision step 926 tries to determine if an occupied
classification track 16 exists in the most preferred group that
can accommodate the train block or a portion thereof.
As
discussed previously, the DTA controller 46 will consider only
those classification tracks 16 that have train blocks marked
"complete", hence the track is open to receive a new train block.
All the other classification tracks 16 in the most preferred
group that hold cars but where the train blocks are not yet
complete are from a logical process point of view marked
"closed". Assuming that the process locates a single occupied
track with a closed train block, hence available to receive a new
train block, the process will then determine if enough space
exists for the new train block on the track.
In a specific and non-limiting example of implementation,
the available space in the classification track equals not the
currently available space on the classification tracks but the
space that is made available to the new train block considering
that train blocks currently occupying the set of classification
tracks will be pulled at certain times in the future (train block
pull profile vs. car arrival profile).
49
CA 02835657 2016-05-06
More specifically, the computation of the available space
takes into account the pull time of the train block that
currently occupies the track and the ETA, or expected switching
time of the cars that make up the train block for which space is
being sought.
For instance, assume a classification track 16
having a 50 car capacity. Train block A made up of 30 cars that
occupies the classification track 16 is scheduled to be pulled at
noon (current time is 10:00 AM). The DTA controller 46 needs to
determine if there is available space for departure train block B
that is made up of 40 in the same classification track 16. The
arrival profile of the cars making up train block B in the
classification track 16 is such that 19 cars will arrive at 11:00
AM, 5 at 3:00 PM and 16 at 3:30 PM.
The computation of the
available space in the classification track 16 is done at
different points in time that generally coincide with the arrival
of the cars making up train block B. For instance, the available
space at the following times will be:
= 11:00 AM - one car;
= 12:00 AM -19 cars, considering that train block A was
pulled;
= 3:00 PM - 24 cars;
= 3:30 PM - 10 cars.
By checking if available space exists at the ETA, or
expected switching time of each car in the new train block, the
process can determine if enough space will exist for it in the
classification track 16. The train block B is deemed to "fit" in
the classification track 16 if for every train block B car that
arrives, space exists to receive it.
CA 02835657 2016-05-06
In determining the time at which cars arrive in the
classification track 16, one option is to use only the ETA of the
cars available from the SRS component 30.
The ETA provides a
rough estimate of the time the cars would be present in the
classification track since it does not take into account the
preparation time for switching such as the mechanical inspection.
Nevertheless, in some applications the ETA can provide a
reasonable indication of the time the cars will arrive in the
classification track 16 such as to make the assessment. Another
more refined option is to use the expected switching time of the
cars which is computed as described earlier.
In the case where the process finds a single classification
track 16 that can accommodate the new train block, then the
process terminates by issuing the switching solution. However,
in the instance where several classification tracks exist in the
most preferred group of classification tracks that can all hold a
complete train block, and that can accommodate the new train
block, hence the new train block "fits" two or more
classification tracks in the most preferred group, then a number
of options arise that are considered by the DTA controller 46 to
find the best solution.
This situation is illustrated in the
flowchart at Figure 9. The process starts at 700. At step 706,
the process will compute the degree of "fit" in each
classification track that can hold the new block. The degree of
"fit" is represented by the Left Over Room (LOR) for each
classification track option. The LOR is the free space in the
classification track that will remain after all the cars of the
new train block cars have arrived. In the above example, the LOR
51
CA 02835657 2016-05-06
at 3:30 will be of 10 cars.
In Figure 9, the DTA controller 46 will select at step 710
the classification track that has the lowest LOR and thus
provides the best "fit". Since LOR is space that is difficult to
use in practice, selecting the classification track with the
lowest LOR results in most cases in a better utilization of the
available space.
When a classification track has been found to accommodate
the new train block, then the records of the DTA controller 46
are marked such that:
= For every car of the new train block all the
classification tracks 16 will be seen as "closed",
hence not available, with the exception of the selected
classification track 16.
This ensures that the
subsequent cars of the new train block will be
constrained to go to the selected classification track
16.
= The selected classification track 16 will appear as
"closed" for every car that belongs to a train block
other than the new train block.
Again, this ensures
that only cars from the new train block are directed to
the selected classification track 16.
The selected
classification track will be released from the "closed"
status only when the new train block is completed, in
other words all the cars from that train block have
been delivered in the selected classification track 16.
52
CA 02835657 2016-05-06
Now assume, for example, that the process under step 926 in
Figure 7 fails to identify an occupied track in the most
preferred track group that can hold the entirety of the new train
block.
The next step is to terminate process step 926 and
initiate process step 928.
Process step 928 is similar to
process step 926 with the exception that it looks for space for
the new train block in the second preferred group of
classification tracks. Similarly, if no space can be found for
the new train block in the second preferred group of
classification tracks, the process continues to step 930 that
will consider the third preferred group of classification tracks.
If no space is available in anyone of the preferred groups
then the process will look for space outside the preferred
groups.
The same pattern described earlier will be repeated.
More specifically, the step 932 will search for an empty
classification track but outside the preferred groups (most,
second and third).
If such an empty classification track is
found, then a switching solution is issued.
Otherwise, the
process continues with step 934 that will consider all occupied
tracks with closed train blocks outside the preferred groups.
If no space for the train block has been found so far, the
process continues with step 936 which is described in greater
detail with reference to the flowchart on Figure 12. This point
in the overall process indicates that no classification track 16
exists that can accommodate the entire train block.
The DTA
controller 46 will now try identifying a classification track 16
that can accommodate most of the train block but not all of it.
53
CA 02835657 2016-05-06
The process starts at step 1402.
At step 1404, the DTA
controller 46 will compute the available space on each set of
most preferred classification tracks 16 with closed train blocks
(i.e. classification tracks 16 that can receive cars from another
train block).
Classification tracks 16 with train blocks that
are still open are disregarded. The computation of the available
space takes into account the pull profile of the existing train
block(s) and the arrival profile of the cars of the current train
block as described earlier.
The result of the available space
computation essentially determines how many cars will fit in each
classification track with a closed train block.
The DTA
controller 46 retains in memory the classification track 16 that
can hold the largest number of cars.
The same computation is performed in connection with the
classification tracks 16 in the second preferred group (step
1406), in the third preferred group (step 1407) and then for
classification tracks (step 1408) other than those in the most
preferred, the second preferred group (step 1406) and the third
preferred group (step 1407).
The results of the four computation operations are compared
at decision step 1410. Generally, the selection logic is designed
to favor a classification track according to the following order
of preference:
= the most preferred group of classification tracks;
= the second preferred group of classification tracks;
= the third preferred group of classification tracks;
54
CA 02835657 2016-05-06
= Tracks that are outside the most preferred, second preferred
and third preferred groups of classification tracks.
This order of preference is applied unless a classification track
at a less preferred level can hold significantly more cars.
One example of decision thresholds is to select a
classification track in the most preferred group unless the
available classification track from the second preferred group
can hold at least 5 more cars. The same or different threshold
can be applied to other preference levels as well. For example,
the classification track returned by step 1407 (third preferred
classification track) is selected if it can accommodate 10 cars
or more than the classification track in the second preferred
group.
Once the decision on which classification track 16 to use is
made and the appropriate records in the DTA controller 46 are
marked to open that classification track only to cars of the new
train block and similarly close the selected classification track
16 to cars from any other train block, then processing is
initiated to determine how to handle the overflow.
Several
options exist:
= Direct the excess cars to rehump tracks 26. This
option is suitable if the number of excess cars is low.
So, for instance, a threshold could be set such that if
the number of excess cars is at or below the threshold
they are directed to the rehump tracks 26.
In a
specific and non-limiting example of implementation,
CA 02835657 2016-05-06
the threshold could be five cars. The DTA controller
46 will then mark its records that the cars which make
up the overflow are to be sent to the rehump tracks 26.
For instance, each car object of the train block can be
marked by the DTA controller 46 to the effect that it
has only two switching options, one being the rehump
tracks 26 and the other the selected classification
track 16.
Since the classification track 16 is full
when the car arrives at the hump, the logic will direct
the car to the rehump tracks 26. When the cars in the
rehump tracks are humped, then the logic is run one
more time and, if space is now available in the
selected classification track, then the switching
solution to direct one or more cars in that
classification track 16 is issued.
= Place the cars of the train block in two separate
classification tracks. In other words, the overflow is
sent to a different classification track 16 instead of
waiting for space to be available in the selected
classification track 16. Under this option, the train
block as far as its processing by the DTA controller 46
is concerned is handled as two separate train blocks,
which are to travel on the same departure train.
In
other words, the selected classification track 16 that
holds the initial part of the train block is considered
to hold a closed train block, in other words no further
cars are expected in that classification track 16 for
the same train block. At the same time, the overflow
is considered from the point of view of the DTA
56
CA 02835657 2016-05-06
controller 46 logic to become a train block and it is
treated as such. The logic starting from step 920 is
performed to find a suitable location for that "new"
train block. Since it will not be desirable to locate
the overflow physically remote from the initial part of
the train block, the logic may be constrained to look
for space only in the most preferred classification
track.
Finally, the logic also needs to take into
account constraints that arise at train block pull time
due to the train block splitting. In
particular, it
would be highly desirable to synchronize the train
block pulling operation on the two classification
tracks such that the train block parts are physically
joined to one another in the departure train.
= Pre-empt the selected classification track (step 938 in
Figure 7). This option is an extension of the second
option above, the exception being that two train blocks
are being created out of a single train block. Recall
that in the previous case, the train block splitting
was only an operation internal to the DTA controller 46
and the result was still a single train block, as far
as the departure train is concerned.
Here, a single
train block creates "officially" two separate train
blocks. The new
train block that is made up of the
overflow has essentially the same properties as the
original train block, such as destination, etc, with
some differences such as the number and identity of
cars that make up the new train block. Moreover, the
original train block also needs to change in that now
57
CA 02835657 2016-05-06
it has fewer cars. Finally, the departing train object
also needs to be updated, since it now contains one
more train block.
Those changes are handled by
modifying the records in the DTA controller 46. Since
the DTA controller 46 is aware of the identity of the
cars making up the overflow, it will:
- Create a new train block object to encompass the
overflow by also copying relevant properties from
the prior train block object (such as destination,
etc.);
- Modify the existing train block object by adjusting
for the cars that have been excised and are now part
of the newly created train block object;
- Update the train object to add to it a new train
block object.
All those changes must also be communicated to the SRC
component 30 such that the railway operations, once the train has
left the hump switch yard 10 can be conducted by taking into
account the existence of a new train block.
The necessary
information can be communicated to the SRS component 30 manually.
This can be done by an operator that will access the system and
make the necessary changes. Another possibility is to allow the
DTA controller 46 to communicate directly with the SRS component
such as to change the records of the SRS component 30.
If the step 938 is answered in the negative, in other words
a switching solution is not possible, the final option is the
58
CA 02835657 2016-05-06
step 940 that issues a switching solution to send the car to the
rehump tracks 26.
In the above examples, the DTA controller 46 is designed to
compute a switching solution and tell the yard master or any
other operator where the car should go. In this embodiment, the
DTA controller 46 assists with the switching process and it is up
to the yard master to validate the choices made by the DTA
controller 46 and then authorize their implementation.
In a
possible variant, not shown in the drawings, the DTA controller
46 can be designed such as to communicate switching commands
directly to the HPCS component 32.
In this fashion, the DTA
controller 46 will cause the HPCS component 32 to implement the
switching solutions, bypassing the human operator. This system
would require a communication link between the DTA controller 46
and the HPCS component 32 over which commands and data can be
exchanged between both entities.
A possible variant to the general process described earlier
in connection with Figures 8 and 9 is to provide a special
treatment of empty cars in order to take advantage of the
inherent flexibility they possess in terms of being substitutable
for one another. Cars that carry goods have to be switched in a
way to reach the destination of the goods. In contrast, a given
empty car does not need to comply with the preset trip plan.
What matters from a customer's perspective is to receive an empty
car; it is far less critical which specific car is being sent
since any empty car (that matches the customer requirements) will
do.
59
CA 02835657 2016-05-06
In summary, the process described in Figures 8 and 9 treats
the empty cars as any other car and they are switched as per the
parameters establishing which train block they go to. Figure 13
shows a variant where the specificity of the empty cars is
recognized by the DTA controller 46 such as to perform
substitutions, wherever possible.
The process starts at 1300.
At step 1302, the DTA
controller will identify all the empty cars in the hump yard 10.
In essence, the DTA controller 46 maintains in the memory 49 a
list of all the empty cars that are currently in the hump switch
yard 10 and that have not yet been switched.
This list is
continuously being updated to take into account cars that are
being switched and cars that are arriving with inbound trains.
Every time an empty car is switched and placed in a
classification track 16, the list is updated to remove that car
from the list.
Similarly, every time a new train arrives, if
that train contains empty cars, they are added to the list.
The DTA controller 46 is capable of distinguishing between
empty cars and cars that are not empty by inspecting the records
associated with the respective car objects available from the SRS
component 30.
The DTA controller 46 computes at step 1304 the expected
switching time of each empty car in the dynamic list maintained
by the DTA controller 46.
The expected switching time is an
information that can be added to the list or it can be cross-
referenced on the basis of the car ID information.
In other
words, the DTA controller 46 can be designed such that it
CA 02835657 2016-05-06
computes the expected switching time for all cars in the hump
yard 10 yet to be switched and the expected switching time for
the empty cars can be extracted on the basis of car ID
information.
At step 1306, the DTA controller 46 will identify all the
train blocks that the switch yard 10 is to make (departing train
blocks) that have not yet been pulled and that contain empty
cars. Again, this identification is made based on the records
provided by the SRS component 30. The inquiry made at step 1306
will essentially produce a list of train blocks that contain
empty cars.
Those departure train blocks are either in the
process of being assembled or will be assembled in the future.
Note that the train blocks identified at step 1306 are defined in
the DTA controller 46 records in terms of specific cars making up
the train blocks. In other words, a train block containing one
or more empty cars specifies unique car ID numbers, not just any
empty car.
At step 1308, the DTA controller 46 will determine if anyone
of the specific empty cars required for the train blocks to be
assembled will be available on time.
Available on time means
that the particular empty car has an expected switching time
prior to the pull time of the block. Step 1308 is expected to
produce a shorter list of blocks containing empty cars where at
least one empty car specified for each block will not be
available on time. This may be caused by the arrival train that
brings the empty car being late. Since the DTA controller 46 is
made aware of the ETA of each car via the SRS component 30, it
61
CA 02835657 2016-05-06
can determine for any given car if it can be switched before the
pull time of the departing train block.
Decision step 1310 determines if an empty car substitution
is possible. Once a block has been identified where an empty car
will be late, the DTA controller 46 looks for other empty cars in
the hump switch yard 10 that can be substituted to the late car.
Since a list of all the empty cars in the hump switch yard 10 has
been compiled at step 1302 and their respective expected
switching times are known, then the DTA controller 46 can
determine by searching that list if there is an empty car having
an expected switching time before the pull time of the block,
hence available to be substituted for the missing or late car.
If a substitution is possible, then the substitution is
performed.
This entails switching the car ID numbers in the
records associated with the two cars.
Specifically, the ID of
the car that is currently available in the hump switch yard 10
replaces the ID of the car that is late in all the records of the
DTA controller 46 and also in the records of the SRS component
30. Similarly, the ID of the car that is presently in the hump
switch yard 10 is replaced by the ID of the car that is late.
Hence, when the car that is late actually arrives it will be
directed to the train block that was to receive the other car.
If no substitution is possible, in other words the decision
step 1310 is answered in the negative, the DTA controller 46 does
nothing and the situation is handled as per the process described
in connection with Figures 8 and 9.
62
CA 02835657 2016-05-06
A variant of the process illustrated in Figure 13 is shown
at Figure 14. The process starts at 1400.
At steps 1402 and
1404, a list is made of the empty cars available in the hump
switch yard 10 and their respective expected switching times.
Those steps are identical to steps 1302 and 1304 described
earlier.
Next, step 1406 identifies the train blocks to be
assembled that contain empty cars, similar to step 1306. At step
1308, the DTA controller 46 will compute a best fit map, trying
to match the available empty cars to the demand, i.e. the empty
car slots in the departure train blocks. The best fit algorithm
can match an empty car to an empty car slot in a departure train
block when the expected switching time for the empty car has not
exceeded the pull time of the departure train block. As a match
is found, the DTA controller 46 will write at step 1410 the car
ID number in all the electronic records of the empty car that is
part of the departure train block. Specifically, the records of
the DTA controller 46 that issue switching solutions will
indicate the particular empty car is to be directed to the
classification track that contains other cars of the block and
also data is communicated to the SRS component 30 such that the
SRS component 30 is made aware of the association of that
specific empty car with the train block.
The embodiment in Figure 14 is different from the embodiment
in Figure 13 in that at the onset a pool of empty cars is created
and as an empty car is needed for a departure train block, then
an empty car is taken from the pool, the choice as to which car
to take is made on the basis of the expected switching time of
the car and the pull time of the departure train block.
63
CA 02835657 2016-05-06
,
,
A possible refinement of the empty car substitution process
is to perform the substitution as described earlier but to
classify the empty cars according to type, style or category. In
many cases, not all empty cars that are placed on the railroad
network can be substituted for one another.
For example, an
empty box car to carry dry goods is not likely to be
substitutable to an empty car to carry liquids, for obvious
reasons.
Accordingly, the above substitution process is
performed in the same manner but for specific car categories.
This allows performing substitution only among cars that can
perform similar or identical functions. Specifically, if a car
to carry liquid goods is late or missing only a similar category
car will be allowed to substitute the missing or late car.
The manner in which this refinement is implemented is to
create car categories in the records of the DTA controller 46.
In a given category, one car can be substituted in terms of
functionality to any other car in the same category. The number
of categories can vary and will depend on the number of different
types of cars in circulation on the railroad network. For each
car category, the substitution logic described earlier is run.
This ensures that, in the case of a substitution, the customer
will receive a car that will match his/her requirements.
Although various embodiments have been illustrated, this was
for the purpose of describing, but not limiting, the invention.
Various modifications will become apparent to those skilled in
the art and are within the scope of this invention, which is
defined more particularly by the attached claims.
64
