waiting lines (queuing)
INFO300
TEAMASSIGNMENT 3: Waiting Lines (Queuing)
Starbucks Downtown
Koby Alonelle, manager of the downtown Starbucks, has requested your assistance on a queuing issue to improve the customer service at the coffee shop. Koby is considering how to restructure the waiting lines to reach an optimal level of staff efficiency and customer service. Observation of arrivals during the morning coffee rush of 7:00AM to 9:00AM shows that an average of 80 customers arrive in the shop each hour. It takes an average of 3 minutes to “process” each customer.
Despite the typical Starbucks recommended service structure, Koby is considering various alternatives to improving customer service by reducing the length of time that customers spend waiting / being served.
PLAN 0: (Current)
: At present, the Starbucks has five baristas on duty, each with a separate waiting line. In other words, currently the store is set up with five separate lines one in front of each of the baristas who take and fulfill the customer order on their own.
PLAN I. The first proposal would designate one employee as a quick-service barista for customers ordering just a standard cup of coffee, a market segment that fills about 30% of all morning sales. Because of their standard order, the barista in the “quick service” line takes an average of just 2 minutes to service a customer. With these customers separated from the rest of the clientele, the average time for registering a typical customer would climb to 3.4 minutes. Under this plan, non-“quick service” customers would choose any of the remaining four lines.
PLAN II. The second plan is to implement a single-line system. All customers could form a single waiting line to be served by whichever of five baristas became available. (The only difference between the current scenario (Plan0) and this proposed Plan II is the line formation – currently it is set up with five separate lines one in front of each of the baristas, this plan II proposes a single line that wraps around with a corral and the next customer will go to the next available barista). This option would require sufficient space for what could be a substantial queue.
PLAN III. The use of an automated coffee machine to custom make your self-serve orders. This automated coffee machine would provide about the same service rate as would a barista, however, since the machine is automated, the service time would be a
constant
(every service time would be exactly the same) 3 minutes. Because some customers may be skeptical of the new self-service, Koby estimates that 20% of customers, primarily frequent customers, would be willing to use this machine – hopefully this percent will increase in the future. Koby would set-up a single queue for customers who prefer the baristas to take the order and make the drink (the remaining 80% of the customers). This line would be served by only four baristas, because of the space requirement for the self-serve kiosk and the extra expense of the technology.
INSTRUCTIONS:
i. For each plan (and subplan – ie. Plans 1 and 3 have two subplans), identify the correct model to use, determine lambda and mu, and number of servers. Create a summary table and include this in your write-up.
ii. For each plan, identify the important performance measures — the average number of customers and the average amount of time that a customer spends waiting and in the system (Lq, Ls, Wq, and Ws) under each of the stated options and compare to existing set-up. HINT: for Plans with multiple “systems” (eg. 30% express customers, 70% regular customers) determine total number of customers (in line, in system) and calculate a weighted average for the time (in line, in system) so you can easily compare performance measures to the other plans. You should include a summary table of for the performance measures for each plan.
iii. Based on your analysis, which option do you recommend? Why?
iv. If you were able to devise a queuing system for this Starbucks, provide 3 specific recommendations that you would implement to improve the overall customer service.