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The Joy of Queueing Operations Management Dr. Mark P. Van Oyen. Filename: queue-lec-1.ppt. POP QUIZ ;- ). WHAT IS A QUEUE? A. The rod (or end of a stick) used in billiards/pool B. A prompt or signal to do something C. A braid of hair worn down the back (pigtail)
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The Joy of Queueing Operations Management Dr. Mark P. Van Oyen Filename: queue-lec-1.ppt
POP QUIZ ;- ) WHAT IS A QUEUE? A. The rod (or end of a stick) used in billiards/pool B. A prompt or signal to do something C. A braid of hair worn down the back (pigtail) D. A waiting line or inventory buffer E. C and D. It’s not the same as “cue” Queueing Picture: A quintuplet of quail, quietly queueing for quills
Queueing Picture: A quintuplet of quail, quietly queueing for quills
Queuing Systems • Queue is a line of waiting customers who require service from one or more servers (service providers represent service capacity - machines, tools, workers, etc.). • Queueing system = waiting room + customers + server + workstations ArrivalsQueue Server(s) Departures
Queueing Happens … But Why? • Queues form whenever current demand (temporarily) exceeds existing capacity to serve. • Variability of Demand: patterns are irregular or random (measure: Std. Dev of job interarrival times) • Service times vary among “customers” or “jobs” (measure: Std. Dev of job service times) • Managers try to strike a balance between efficiently utilizing resources (which comes at the price of high WIP and long cycle-times) and keeping customer satisfaction high (which usually requires lower utilization levels). • Waiting increases when the variability of arrival times and/or service times increases.
How many examples of queues can you think of? (REAL WORLDand atLUC) LUC • elevators • registration • counselors • office hours • Flapjaws • parking gar. • graduation • “Simple” … waiting in line for • Lunch/dinner at cafeteria • Video rental • Banking • Buying groceries • Complex • Service at sit-down restaurant • Amusement parks (network of queues) • Waiting for train/bus ride • Traffic congestion & waiting for traffic signals • ordering a Harley Davidson, then waiting for it to come.
RAISE YOUR HAND IF It depends… if you are the customer or owner! • You like queues • You are indifferent to queues • You hate queues
OTHER QUEUES • Parts on an assembly line (with random arrival/production times) • Planes waiting to land/take off/load/unload • Rides waiting to load/unload at Disney World • Trucks/trains/ships waiting at loading docks • Orders waiting to be handled • Payments waiting to be mailed • 30% off sale at your favorite department store What country has the #1 practitioners of queueing? What company is the “genius of queueing”? (managing wait at the park or in the theater)
And, while you wait to enjoy the feature presentation, we have a cartoon for you...
Where Did All the Time Go? In a lifetime, an average U.S. Citizen will spend… • 0.5 years sitting at stoplights • 0.67 years opening junk mail • 1 year looking for misplaced objects(triple that if you are unlucky enough to be a professor ;-( • 2 years unsuccessfully returning phone calls • 4 years doing housework • 5 years waiting in line(E-commerce to the rescue??, or just more time waiting on-line!) • 6 years eating Source: US News & World Report 1-30-89, p. 81.
Prof. _____ What frustrates you most about queues? TIME LOSS/COST - people remember long waits! FAIRNESS, VARIABILITY BOREDOM
WHAT WASYOUR WORST QUEUEING EXPERIENCE ? E.g. Being late to the session you chaired due to a 15 minute elevator experience WHAT MADE IT SO BAD ? -length of wait -conditions of wait -fairness -impact on subsequentdependent events
Who Cares About Queueing? • Service Operations • random customer arrivals • service time variability • Manufacturing/Production Systems • variability in machine processing times, routing • variability in customer demand • Can you think of a business which does not care about queueing? The government is not a business ;-)
Psychology of Waiting • Fill waiting time in positive way: • improve waiting environment with better furnishings, music, mirrors. • air commercials, allow people to wait in bar at restaurants, provide beverages or toys for children. • Convey sense while waiting that service has started: • hand out menus, water, & bread to waiting diners • have waiting patients fill out medical forms • moving patient from waiting room to examining room
Psychology of Waiting • Develop strategies for easing waiting anxieties(This line isn’t moving! … Have I been forgotten?) • acknowledge waiting customer’s presence periodically, tell customer expected waiting time. • Develop strategies for maintaining perceptions that waiting is fair: • avoid violations of first-come, first-served (FCFS) queuing policy when customers are viewed as being equal.
Physics & Psychology of Waiting • Waiting behaviors: • Jockeying. • reneging. • balking. • Innovate the process: Can the customer serve herself/himself? • Self-serve gas, fill-your-own-soda-pop, Automatic Teller Machine, bag-your-groceries • Web sites • FAQ’s (frequently asked questions) • Online Diagnostics - give users the decision support (artificial intelligence) that in-house trouble-shooters use!
Laws of Service • Law of expectation vs. perception: if customer receives better service than expected, customer is satisfied, and business may benefit from “trickle-down effect” of good word-of-mouth. • It’s hard to play “catch-up ball” law: first impressions influence rest of service experience, so making wait period as pleasant as possible is crucial (otherwise, customers may not come back!).