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Waiting Lines & Simulation
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Waiting Lines &
Simulation
by-
Navitha Pereira
Vijay M V
Navya G Nayak
Adarsh K V
Sanath Bhaskar
4. Waiting Lines
Waiting Lines are commonly found wherever customers arrive
randomly for services
• Waiting lines are non-value added occurrences
• Customers regard waiting as something negative
• For businesses, the costs of waiting come from lower productivity and
competitive disadvantage
• Service Designers and Managers needs to consider the impact of waiting
lines
5. Waiting Lines
Managerial Implications of Waiting lines:
Cost of waiting space
Possible loss of business from
waiting customers
Possible loss of goodwill
Possible reduction in customer
satisfaction
1
2
3
4
Disruption in other business
operations/customers
5
6. Waiting Lines
Goal of Waiting Lines:
• Minimize total cost.
Total Cost = Customer
waiting cost +
Capacity cost
• Balance the total cost of
service with the cost of
customer waiting for
service.
7. Waiting Lines
Characteristics of Waiting Lines:
• Population source:
1) Infinite-source situation
2) Finite-source situation
• Number of servers (channels):
1) Single channel
2) Multiple channels
• Arrival and Service patterns
• Queue disciplines (order of service)
8. Waiting Lines
Measures of Waiting Lines:
Average number of customers waiting
Average time
customers wait
System
utilization
Implied cost of given
level of capacity and its
related waiting line
The probability that an
arrival will have to wait
for service
9. Waiting Lines
Case of Walt Disney
Key Issues:
• Walt Disney realised that customers waiting in lines doesn’t add to their
enjoyment.
• Waiting lines will not generate revenue.
Solution:
• Used a reservation system called FastPass.
Result:
• Customers are happier.
• Hence the park’s potential for additional revenue increased.
11. Capacity Planning
A
B
C
D
Capacity - ability to achieve,
store or produce.
In OM - output rate of a
production or service facility.
Capacity planning - process of
establishing the output rate that
may be needed at a facility.
E.g. Indian Railways Capacity planning will
consider number of booking counter to be
made available for the Public.
12. Capacity Planning
fewer booking counter -> long queues
-> more waiting time for customers.
Capacity decisions in service
systems made on the basis of
impact on the customers
Waiting time determines service
quality in service systems.
13. Basic structure of Queuing system
• Customer requiring service are generated
over time from a calling population(source).
• Customers enter the queueing system and
join the waiting line (queue.)
• Queue discipline used to select a member.
• Service performed by servers.
• Customer leaves the queueing system.
14. Basic elements of waiting line model
Routing
Infinite
Finite
Calling Population
Pattern
Rate
Stages
Servers
Single, bulk, special group
Capacity
Queue length, waiting time, utilization, cost-based
Single, multiple
Single, multiple
Single serial network
FCFS,LCFS,random
Markovian, general distribution, deterministic
Finite, infinite
Markovian, General Distribution, deterministic
System Structure
and Parameter
Queue Parameter
Arrival Parameters
Performance
Metrics
Service Parameter
15. System configuration in queuing systems
Single server single stage Single server multiple stage
Multiple server single stage Multiple server multiple stage
18. Simulation
Simulation is a descriptive technique in which a model of a process is
developed and then experiments are conducted on the model to evaluate its
behavior under various conditions.
• Many situation are too complex to permit development of a mathematical
solution.
• Simulation models are fairly simple to use and understand.
• It enables the decision maker to conduct experiments on a model.
• It can be used for a wide range of situation.
• There have been numerous successful applications of these techniques.
19. Steps in the simulation process
01 02 03 04
Identify the problem
and set objectives
Develop the
simulation model
Test the model to be
sure that it reflect the
system being studied
Develop one or
more
experiments
05 06
Run the simulation and
evaluate the results
Repeat steps 4 and 5 until you
are satisfied with the results
21. Computer Simulation
• Most real-life simulations involve the use of a computer.
• Computers offer relatively quick and easy means of obtaining
results.
• Simulation Languages – GPSS/H, GPSS/PC and RESQ
• Some simulation packages have narrow focus on queuing or
network problems.
A computer simulation is the usage of a computer for the
imitation of a real-world process or system.
25. CAST Summary
The simulation describes the key elements
of SESAR Airport Operations Plan (AOP)
and Airport Performance Monitoring.
CAST is a fast time simulation model developed by
Airport Research Centre (ARC) Germany.
CAST (Comprehensive Airport Simulation Tool) is applied for Airport
Collaborative Decision Making Concept(ACDM) to develop the quality
of Airport and Network Operations through sharing of accurate
information.
26. CAST Summary
CAST improves the situational awareness
among airport partners with a feature called
ATV (Airport Transit View) to identify the
trajectory performance and re-enforce the
collaborative decision-making process.
When the agreed thresholds are
exceeded, CAST raises an ALERT to all
the connected centers. This Alert is sent in
the form of a warning to the AOP to
improve the overall operations
predictability.
