A presentation accompanying a paper on the subject of railway schedule optimisation and infrastructure optioneering. Presented before the Institution Of Railway Engineers in 2007 by author David Caldwell

1. IRSE 2007 Technical Conference- Brisbane
Application of Problem Space Search to Heavy Haul
Scheduling
Alex WARDROP & David CALDWELL

2. What is scheduling?
 “Scheduling” is a broad term and can include crew rostering,
maintenance scheduling and train planning (timetabling)
 Here the main interest is train planning
 Train plans may be developed around the constraints of crew rostering,
and in cooperation with maintenance scheduling
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3. Train Planning
 Train planning is placing a set of train requirements over a railway
network
 Train requirements are the trips that train operators want to operate
over a given period of time to meet commercial requirements (moving
stuff)
 The aim of the train planner is to move these trains to their required
destinations with as little delay as possible
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4. Train Planning
Train demand (e.g.
Network (e.g. running times, trains, origins, stops, Maintenance
loop lengths, safeworking, destinations) requirements
loader capacity) Train performance
and requirements
Crew rostering/
Other
industrial requirements
Constraints
Maintenance
Train planning
scheduling
Day of Operation
planning
Maintenance
Operations
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5. Developing a timetable
 In a manual process, the highest priority trains are “drawn” on the plan
first
 Lower priority trains are stopped for passes in preference to stopping
high priority trains
• Order of priority- “two legs, four legs, no legs”
 This means that passenger trains go through the route on the minimum
running times
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6. The heavy-haul problem
 While the most densely utilised heavy-haul lines are double track, the
majority of Australia’s heavy-haul track mileage is on single-track line
 A major challenge is figuring out how to stop and pass trains, and when
to admit them to the next section
 This has to be done with consideration for
both safeworking requirements and
refuging opportunities
 A train plan looks like this, showing the
train ID and stops
Distance
 Lines are coloured to represent an
important attribute, like train length,
running time, or priority
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7. What is Problem Space Search?
 Unlike a mathematical algorithm which seeks to find an exact solution,
Problem Space Search employs a heuristic (or trial and error
mathematical process) to develop many feasible solutions to a problem
 These solutions can then be scored against an objective function and
ranked
 Research undertaken jointly by the University of South Australia and
the former TMG International found that the technique was applicable to
rail scheduling
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8. Application of Problem Space Search
 By applying perturbations to crossing delays of trains moving through a
network, the order in which trains meet is varied, and so the orders of
crossings changed
 Thousands of different valid train plans can be generated in a matter of
seconds
 These valid solutions can then be evaluated and ranked for their
performance against criteria such as delays and cost
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9. Application of Problem Space Search
 Developing a timetable by manual techniques generally takes months
 An automated train plan optimising technique has obvious direct
benefits for train planning, reducing the time to produce a timetable,
and improving its “quality”
 The huge reduction in the effort required to develop a timetable means
that timetables can be quickly manipulated very close to the
implementation horizon, and still produce optimal results
 Timetables can also be easily developed for speculative purposes
(“what if…” scenarios)
 Software using Problem Space Search for these purposes has been
developed
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10. Information flow
TRAIN CHARACTERISTICS
RAIL NETWORK
DESCRIPTION Length
Track layout Running time class
Refuge locations Priority INPUT TRAIN REQUIREMENTS
Junction locations Nominal despatch times
Sectional running times Days of operation
Safeworking systems Dwell times
RailSched Dependencies between
services
Near-optimal Line Capacity
timetable report
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11. Typical Inputs
Track Infrastructure- links and nodes
Bi-directional line Refuge
Crossovers
Uni-directional line Station name
Crossing loop
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12. Output: optimised train plan
BW4 is a high priority train
MB3 is a low priority train
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13. Output: Capacity utilisation
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14. Application
 The Problem Space Search technique is applied for both timetabling
and strategic infrastructure planning
 An integrated scheduling system, ScheduleMiser ™ was developed for
BHP Billiton
 A more general scheduling tool, Rail//Sched ™ is the subject of
ongoing development for the Australian Rail Track Corporation
 In both cases the general data requirements and outputs are the same,
thought the interfaces differ significantly, according to specific
requirements
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15. Case study: ScheduleMiser
 ScheduleMiser was developed to represent BHP Billition’s iron ore
moving process, rather than looking at trains in isolation
Material at mine loader
Time it takes to load a rake
Time it takes to re-stack the
stockpile at the loader
Desirability of different rake
configurations
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16. Translating BHP requirements
 The user specifies production requirements, as well as other
operational variables like loader availability and rake locations
 ScheduleMiser builds trains of one, two or three rakes to satisfy
production
 Day to day operational conditions, like TSRs and track possessions, are
also configured
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17. The BHP requirement
Ore requirements at
Shipping port
Rolling stock, mine, Track availability
unloader and network (possessions)
configuration
ScheduleMiser
Dumper report Rake report
Optimised timetables and
train plan
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18. Typical schedule output
 The user configures all the requirements and runs the schedule
resolver
 A train plan, similar to the following, is resolved
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19. Planning close to the horizon
 Need to be able to rapidly review timetable for changing train
requirements, e.g. out of order running
 Developing amended timetables close to the event
 WorleyParsons, with the assistance of a Commercial Ready grant, is
currently integrating automated scheduling with real-time GPS train
location information
 Train locations can be continuously updated in the model, and a
timetable with minimum delay calculated almost immediately
 There is another significant application of automatic timetable
generation…
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20. Strategic Infrastructure Planning
 Why different scheduling scenarios need to be considered
• Which loops should be lengthened or moved?
• Will changing the safeworking system (i.e. eliminating token
exchange delays) have a practical effect on capacity?
• Will automating points (and reducing route-setting delays) and
improving turn-out speeds have a practical effect?
• What is the effect of running some longer trains which are excluded
from more loops?
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21. Considering the future
DEMAND
SCENARIOS
OPERATIONS SCENARIOS
SCHEDULING
INFRA - TRAINS
STRUCTRE
WHAT IS THE MOST COST -EFFECTIVE?
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22. Case Study: Rail//Sched
 The ARTC is developing its network for expected traffic growth
 Their 2005 Hunter Valley strategy anticipates that from 2006 to 2010,
tonnage between Musswellbrook and Antiene will approximately triple
from about 20MTpa to about 60MTpa
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23. 23
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From ARTC 2005 Hunter Valley Coal Network Capacity Improvement
Strategy, figure A, pii
Hunter Valley growth

24. The effect of growth
 ARTC developed infrastructure improvement plans to satisfy this growth
 To verify that delay would remain at an acceptable level, ARTC
developed proposed infrastructure schemes (varying over time), and
then developed experimental future train requirements to meet
operators’ train requirements/ tonnages
 ARTC then used Rail//Sched to generate hypothetical timetables for the
increased network usage
 Once these timetables were generated, they were assessed for relative
changes in delay compared with current operations
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25. ARTC’s application
Develop input timetables
 Expectedly, when traffic (train types and despatch
times of projected traffic)
levels increase, but the Describe infrastructure
scenario (s)
network remains Pre-process (add noise to
despatch times)
unchanged, average
delay per train and travel
RAIL//SCHED
times increase
 The process applied to
assess infrastructure
improvements…
Optimised timetables Average Delays
Post processing (Excel)
Normalised
dimensionless delay
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26. ARTC’s application
 The types of network variables that are typically considered are
safeworking, loop lengths, loop locations and additional tracks
 One component of ARTC’s strategy to meet projected demand is the
Antiene to Grasstree duplication
 Duplication by 2008, proposed in the strategy, reduces delays to below
the levels in early 2006
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27. Modelling delay
Modelled Hunter Valley Network Performance
35
MUA
Expected delay per train
SLR
GTR
Delay per train reducing
(dimensionless time)
30
in first half of 2008
ANT
25
4th quarter 2006
DRJ
1st quarter 2007
20 2nd quarter 2007
3rd quarter 2007
4th quarter 2007
15 1st quarter 2008
2nd quarter 2008
NDC
10
NJM
Duplication of
Antiene -
ACS
Grasstree in
MOC
5 first half of
BNX
MBH
2008
BEL
WHM
MB1
MDX
SGL
CAM
KIY
0
NEWCASTLE MUSWELLBROOK
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28. Benefit for planning
 Being able to quickly generate these speculative train plans (and
calculate delay) is very helpful for considering
• Whether a proposed infrastructure plan is a going to satisfy
requirements
• Which projects should take priority
• Whether changing traffic demands will adversely effect delay (and
operators’ costs)
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29. Conclusion
 Scheduling is at the core of railway operations
 Train plans which reduce the amount of delay per train improve the
capacity and efficiency of the railway
 Optimisation of train plans by application of the problem space search
technique is much faster than manual techniques
 Computer generation of train plans makes it possible to experiment with
effects of train and infrastructure changes, and assess the usefulness
of capital projects
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