Managing Waiting Lines

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Managing Waiting Lines
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(No Transcript)
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Lines and Waiting
Every day I get in the queue, that waits for the
bus that takes me to you Pete Townshend,
Magic Bus
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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

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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

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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).

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Laws of Service

• Maisters First LawCustomers compare
  expectations with perceptions.
• Maisters Second LawIs hard to play catch-up
  ball.
• Skinners LawThe other line always moves
  faster.
• Jenkins CorollaryHowever, when you switch to
  another other line, the line you left moves
  faster.

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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

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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

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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)

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The Art of Service RecoveryTo 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

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Essential Features of Queuing Systems
Renege
Arrival process
Departure
Queue discipline
Calling population
Service process
Queue configuration
No future need for service
Balk
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Arrival Process
Arrival process
Static
Dynamic
Random arrivals with constant rate
Random arrival rate varying with time
Facility- controlled
Customer- exercised control
Appointments
Price
Accept/Reject
Balking
Reneging
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Distribution of Patient Interarrival Times

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Temporal Variation in Arrival Rates

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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)
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Queue Configurations
Multiple Queue
Single queue

Take a Number

Enter
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4
2
8
6
10
12
7
11
9
5
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Queue Discipline
Queue discipline

Static (FCFS rule)
Dynamic
selection based on status of queue
Selection based on individual customer attributes
Number of customers waiting
Round robin
Priority
Preemptive
Processing time of customers (SPT rule)
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Outpatient Service Process Distributions

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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

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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?

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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.

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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.

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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 Pizzas performance and customer
  service?