Managing Waiting Lines. Lines and Waiting Every day I get in the queue, that waits for the bus that...
-
Upload
dale-dodgson -
Category
Documents
-
view
223 -
download
1
Transcript of Managing Waiting Lines. Lines and Waiting Every day I get in the queue, that waits for the bus that...
Managing Waiting Lines
Learning Objectives
• Describe how queues form.
• Apply Maister's two “laws of service.”
• Discuss the psychology of waiting.
• Describe the essential features of a queuingsystem.
• Explain the equivalence of Poisson arrivalrates and exponential time between arrivals
Lines and Waiting
“Every day I get in the queue, that waits for the bus that takes me to you …”
Pete Townshend, Magic Bus
Where the Time Goes
In a life time, the average
American will spend--
SIX MONTHS
Waiting at stoplights
EIGHT MONTHS
Opening junk mail
ONE YEAR
Looking for misplaced 0bjects
Unsuccessfully returning
TWO YEARS phone calls
FOUR YEARS Doing housework
FIVE YEARS Waiting in line
SIX YEARS Eating
Cultural Attitudes
• “Americans hate to wait. So business is trying a trick or two to make lines seem shorter…” The New York Times, September 25, 1988
• “An Englishman, even when he is by himself, will form an orderly queue of one…” George Mikes, “How to be an Alien”
• “In the Soviet Union, waiting lines were used as a rationing device…” Hedrick Smith, “The Russians”
Waiting Realities
• Inevitability of Waiting: Waiting results from variations in arrival rates and service rates
• Economics of Waiting: High utilization purchased at the price of customer waiting. Make waiting productive (salad bar) or profitable (drinking bar).
Laws of Service
• Maister’s First Law:Customers compare expectations with perceptions.
• Maister’s Second Law:Is hard to play catch-up ball.
• Skinner’s Law:The other line always moves faster.
• Jenkin’s Corollary:However, when you switch to another other line, the line you left moves faster.
Remember Me
• I am the person who goes into a restaurant, sits down, and patiently waits while the wait-staff does everything but take my order.
• I am the person that waits in line for the clerk to finish chatting with his buddy.
• I am the one who never comes back and it amuses me to see money spent to get me back.
• I was there in the first place, all you had to do was show me some courtesy and service.
The Customer
Psychology of Waiting• That Old Empty Feeling: Unoccupied time goes slowly• A Foot in the Door: Pre-service waits seem longer that
in-service waits• The Light at the End of the Tunnel: Reduce anxiety
with attention• Excuse Me, But I Was First: Social justice with FCFS
queue discipline• They Also Serve, Who Sit and Wait: Avoids idle service
capacity
Approaches to Controlling Customer Waiting
• Animate: Disneyland distractions, elevator mirror, recorded music
• Discriminate: Avis frequent renter treatment (out of sight)
• Automate: Use computer scripts to address 75% of questions
• Obfuscate: Disneyland staged waits (e.g. House of Horrors)
The Art of Service Recovery“To err is human; to recover, divine”
• Measure Cost of Lost Customer
• Listen Carefully
• Anticipate Need for Recovery
• Act Fast
• Train Employees
• Empower the Frontline
• Inform Customers of Improvement
Essential Features of Queuing Systems
DepartureQueue
discipline
Arrival process
Queueconfiguration
Serviceprocess
Renege
Balk
Callingpopulation
No futureneed for service
Arrival Process
Static Dynamic
AppointmentsPriceAccept/Reject BalkingReneging
Randomarrivals withconstant rate
Random arrivalrate varying
with time
Facility-controlled
Customer-exercised
control
Arrival process
Distribution of Patient Interarrival Times
0
10
20
30
40
1 3 5 7 9 11 13 15 17 19
Patient interarrival time, minutes
Rela
tive
freq
uenc
y, %
Temporal Variation in Arrival Rates
0
0.5
1
1.5
2
2.5
3
3.5
1 3 5 7 9 11 13 15 17 19 21 23
Hour of day
Avera
ge ca
lls pe
r hou
r
60
70
80
90
100
110
120
130
140
1 2 3 4 5
Day of week
Perc
enta
ge o
f ave
rage
dai
ly
phys
icia
n vi
sits
Poisson and Exponential Equivalence
Poisson distribution for number of arrivals per hour (top view)
One-hour
1 2 0 1 interval
Arrival Arrivals Arrivals Arrival
62 min.40 min.
123 min.
Exponential distribution of time between arrivals in minutes (bottom view)
Queue Configurations
Multiple Queue Single queue
Take a Number Enter
3 4
8
2
6 10
1211
5
79
Queue Discipline
Queue
discipline
Static(FCFS rule)
Dynamic
selectionbased on status
of queue
Selection basedon individual
customerattributes
Number of customers
waitingRound robin Priority Preemptive
Processing timeof customers
(SPT rule)
Outpatient Service Process Distributions
0
5
10
15
1 11 21 31 41
Minutes
Relat
ive fr
eque
ncy.
%
0
5
10
15
1 11 21 31 41
Minutes
Rela
tive
frequ
ency
, %
0
5
10
15
1 11 21 31 41
Minutes
Rel
ativ
e fre
quen
cy, %
Service Facility Arrangements
Service facility Server arrangement
Parking lot Self-serve
Cafeteria Servers in series
Toll booths Servers in parallel
Supermarket Self-serve, first stage; parallel servers, second stage
Hospital Many service centers in parallel and series, not all used by each patient
Topics for Discussion• Suggest some strategies for controlling variability in service
times. • Suggest diversions that could make waiting less painful.• Select a bad and good waiting experience, and contrast
the situations with respect to the aesthetics of the surroundings, diversions, people waiting, and attitude of servers.
• Suggest ways that management can influence the arrival times of customers.
• What are the benefits of a fast-food employee taking your order while waiting in line?
Interactive Exercise
The class breaks into small groups with at least one international student in each group, if possible. Based on overseas travel, each group reports on observations of waiting behavior from a cultural perspective.
Eye’ll Be Seeing You
• How are Maister’s First and Second Laws ofService illustrated?
• What good and bad features of a waiting processare evident?
• How should Dr. X respond to Mrs. F’s letter?
• How could Dr. X prevent future incidents?
• Should customers be rewarded for offeringconstructive criticism?
Pronto Pizza
• Draw a process flow diagram and identify the bottleneck operation.
• Calculate the expected waiting time in the order preparation queue. Compare this value with your simulation result.
• Use the ServiceModel computer simulation software and the Pronto.pkg file to determine the number of drivers that minimizes the total cost of salaries and guarantee discounts.
Pronto Pizza (cont.)
• Based on your simulation recommended staffing level, what is the probability of paying off on the guarantee?
• What do you think of this service guarantee policy?
• What other design or operating suggestions could improve Pronto Pizza’s performance and customer service?