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this research, the crew rescheduling approach will be explored in an attempt to tackle
the problems of UE related to crew members based on realistic situations.
3.2.2 Complete System versus Additional System
A choice has to be made to either to propose a complete system that can build schedules from scratch or make an addition to the system that can connect to the existing
scheduling system. The complete system means the system capable of finding optimum schedules and maintaining the schedules in everyday operation. However, an additional
system will only maintain the existing schedules produced by the existing system. For this research, we will concentrate on the additional system because of the reasons
discussed below. This research focuses on solving problems arising with UE that happen in everyday
operation on crew schedules, and not on finding optimum schedules. Thus, it is better to concentrate on solving this particular problem rather than widening the scope. From the
interviews, it can be seen that the management is satisfied with the scheduling system, but not when it comes to managing it. Wren et al. 2003 also suggest the same, that any
automated rescheduling system can rely on the data produced by TRACS II. In addition, research into finding optimum schedules began in the 1960s and has reached maturity.
So the best approach is to use the current method and concentrate on solving the unpredictable events problem.
3.3 The Proposed Automated Crew Rescheduling System
Before we describe the proposed approach, we model the process to understand the current practices at bus companies in London. The models are presented based on the
understanding from interviews as discussed in Chapter Two, and also informal discussions with crews and a supervisor.
3.3.1 Modelling the Current Practices
A scheduler is a person who is responsible for producing schedules for a garagedepot. One of the schedules is the crew schedule. The purpose of crew schedules is to show all
the duties on a routes and its activities with time and location. After crew schedules
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are ready, a scheduler will assign all duties to crews according to the agreement with trade unions. This process is called crew assignment. Then crews will work according
to their assignment duties. Figure 3.2 shows the ideal situation when no UE takes place. There is no need of supervisors to manage daily operation.
CREW SCHEDULES
CREW ASSIGNMENTS
CREWS
Figure 3.2: The Process in Ideal Situation
However, in reality UE take place almost every day, that is why supervisors are needed to manage them as discussed in Chapter Two. Supervisors are responsible for making
any necessary adjustment or changes to crew schedules and crew assignments when UE take place. Currently, it is done manually at garages. Figure 3.3 shows the function of
supervisors in managing daily operation.
CREWS CREW
SCHEDULES CREW
ASSIGNMENTS
SUPERVISOR
Figure 3.3: Supervisor Manage Daily Operation
One of the tasks of supervisors is to perform crew rescheduling whenever UE take place. Figure 3.4 shows the rescheduling process that currently happens in bus
companies in London. It starts when an event happens. Then supervisor who is in charge of the bus operation obtains details of the event and classifies it as to whether it
is possible or not to reschedule the crew. There are some events such as absent or
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unavailable due to accidents that do not allow for rescheduling. Then the supervisor’s decision is to straight away use a spare crew. However, in the case of events such as,
late, delay or unavailable for a short time, then it is possible to continue the rescheduling process. The supervisor will try to reschedule the crew and find a suitable
crew that could replace himher. If the supervisor can find a match to replace himher then the supervisor will make any necessary changes. However, when replacement is
not possible, spare crew is used to replace the unavailable crew. The proposed system is intended to automate the rescheduling process, so it will provide quick and optimum
solutions to the supervisor. The next subsection will explain the proposed system.
Reschedule Crew? Details and
Classify the Event
Use Spare-Crew No
Rescheduling Process
Yes
Any Match?
No
Change Crew Yes
Figure 3.4: The Rescheduling Process
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3.3.2 Overview of the Proposed Crew Rescheduling System
