Case Study: Service Processes The following case about a local coffee shop explores the topic of service process design. As you read though the case, think about how the new drive-through process can be made into a positive experience for the shop's environmentally-minded clientele. Tree Frog Caf is a new coffee and sandwich shop that features organic products and ingredients. The owners value sustainable business practices and urban design and want to encourage their customers to walk or bike to their store, or at least to come in and spend some time with their neighbours (and of course, browse the product selection). One challenge the owners face is that the retail site they have chosen came with an existing drive-through window system and lane in the parking lot. At first, the owners blocked off and didn't use the drive-through system, but their customers have been asking about it, citing the busy parking lot and convenience of staying in their cars in poor weather. The owners of the Tree Frog Caf have decided to investigate the impact opening the drive-through might have on their business and on the environment. Consider a typical busy morning at the Tree Frog Cafe: about 60 customers arrive per hour (the number of arrivals is Poisson distributed). The Tree Frog Cafe uses mobile ordering and order kiosks, so that no customers wait before ordering. Instead, all the time they spend waiting and 'in service' is spent waiting for the baristas and kitchen to prepare their food and drink order. The caf can prepare one customer's order in an average of 45 seconds (service times are exponentially distributed), and only works on one customer's order at a time. Each customer buys some food and/or drinks, with an average profit margin to the caf of $3 per customer. Also, 10\% of customers will buy a non-food product, with an additional average profit margin of $S per purchase. If Tree Frog Caf opens the drive-through, they expect that their total number of customers in the morning will increase by 20%. Of this new total, they figure one third will use the drive-through. Assume that drive-through customers also use mobile ordering, order ahead of time, or that there are enough drive-through ordering stations that customers never have to wait to place their order. They only have to wait for the cafe to prepare their order. Service times for drive-through and walk-in customers will remain the same. Drive-through customers buy the same amount of food and/or drinks as walk-in customers, but The owners of the Tree Frog Cafe are considering two approsches to running the drive-through. The first is to treat all customers equally, serving them in the order they arrive at the restaurant regardless of whether they are drive-through or walk-in customers. However, they know that idling cars emit carbon dioxide, estimating that for every 10 minutes a car idles it emits 0.5kg of carbon dioxide. So the second approach they are considering is to (quietly) prioritize the drivethrough customers. In this plan, they would always serve a drive-through customer first, even interrupting the service of a walk-in customer. The internupted service of a walk-in customer can be resumed once there are no drive-through customers waiting. The owners believe this will reduce the idling cars' carbon dioxide emissions, without upsetting their walk-in customers too much. Help the Tree Frog Caf decide what to do with its drive-through. Which plan makes the most money? Which plan is best for the environment? Can a compromise be found with carbon offsets? 3. Perform the following calculations (see example. 7.1, pg.226 in text) - for both in-house and drive-through examples. Assuming Poisson arrivals and exponential service. Be sure to show your work. i. Utilization of the service ii. Average number in the waiting line iii. Average number in the system iv. Average waiting time in line