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Table 8.2 Details of Autohaus diagnosis model
Arrival process issue
Resulting model structure
When do autos arrive?
1) Strictly before the ofﬁcial start
of service (9:00 am)?
2) All day long (5:00
Review of the choices available:
1) This is the simplest choice to deal with as a
simulation modeler, but maybe not very customer
2) This is a much more complex modeling situation.
Our choice—1) This assures that the days demand is
available prior to starting service.
How will the randomly arriving
autos be assigned to service
As an auto arrives, its demand for service must be
determined, and only one type of service will be
assigned per auto. Autos will be placed in one of 3
queues, each with a particular service demand type
(Engine/electrical Diagnostics, etc.). The autos will be
served according to a ﬁrst-come-ﬁrst-served service
discipline. The distribution of arriving autos will be
based on a Poisson (more on this later) distribution.
Our choice—Three service queues with
ﬁrst-come-ﬁrst- served service discipline; random
arrivals of autos; random service types.
What happens to autos not served
on a particular day?
This is also a relatively simple question to answer. They
must leave the facility by close of business since they
are there for diagnostic service only. This also
eliminates the need to track vehicles that already in
queues before the morning arrivals.
Our Choice—Cars are cleared from queues at the end
of the day.
Service process issues
Resulting model structure
How will service be initialized
A queue discipline of ﬁrst-come-ﬁrst-served suggests
that this is how service will be administered for the 3
types of service. Thus, we must keep track of vehicles
in queues. These queues will also represent the 3 bays
where a single mechanic is stationed.
Our Choice—In accordance to ﬁrst-come-ﬁrst served,
the auto at the head of the queue will receive service
How will service times be
determined: empirical data or
Empirical data is data that is recorded and retained over
time. Subjective opinion comes from experts that
supply their opinion. Wolfgang has a very good sense
of the time required to perform the three service types.
Our Choice—In the absence of empirical data, we will
use Wolfgang’s subjective (expert) opinion.
complex. The bays that are performing various types of service begin to operate on
the available queues of autos. This requires that autos requesting a particular type
of service be available (demand) and that service capacity (supply) for the service
also be available, as noted in the diamond Is Service Available for Next Auto? As
the mechanic in the bay administers service, the uncertain service time is eventually