The Joy of Queueing Operations Management Dr. Mark P. Van Oyen

1. The Joy of Queueing Operations Management Dr. Mark P. Van Oyen Filename: queue-lec-1.ppt

2. 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

3. Queueing Picture: A quintuplet of quail, quietly queueing for quills

4. 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

5. 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.

6. 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.

7. RAISE YOUR HAND IF It depends… if you are the customer or owner! • You like queues  • You are indifferent to queues  • You hate queues 

8. 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)

9. And, while you wait to enjoy the feature presentation, we have a cartoon for you...

10. 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.

11. Prof. _____ What frustrates you most about queues? TIME LOSS/COST - people remember long waits! FAIRNESS, VARIABILITY BOREDOM

12. 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

13. 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 ;-)

14. 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

15. 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.

16. 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!

17. 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!).