Drive Through Restaurant Back to simulation

Model name: Drive-Thru-1, available on Simulation-for-Education.

Based on Introduction to Simulation by R.G. Ingalls, in Proceedings of the 2008 Winter Simulation Conference

Copyright Gerd Wagner (CC BY-NC), created on 12/7/2016 with the Object Event Simulation (OES) framework OESjs, last modified on 1/9/2019 | OESjs Credits

Classification tags: business operations management, DES, next-event time progression, activity-based process modeling

System Narrative

As a car enters the drive thru from the street, the driver decides whether or not to get in line. If she decides to leave the restaurant, she counts as a lost customer. If she decides to get in line, she waits until the menu board is available. At that time, she gives the order to the order taker. After the order is taken, two things occur simultaneously:

the driver pulls forward if there is room, otherwise she has to wait at the menu board until there is room to move forward.
The order is sent back to the kitchen where it is prepared with some delay.

As soon as the driver reaches the pickup window, she pays and picks up her food, if it is ready. If the food is not yet ready, she has to wait until her order is delivered to the pickup window.

The objective of the simulation is to analyze performance during peak periods to see how long customers spend waiting in line, how often customers pass by ("balk"), and what the utilization of the kitchen is.

Model Description

The drive thru is modeled as a system with order processing activities performed at three service points with queues: the order taking at the menu board, the order preparation at the kitchen and the order pickup at the pickup window. The model includes four object types: MenuBoard, Kitchen, PickupWindow and Customer, one event type: CustomerArrival, and three activity types: OrderTaking, OrderPreparation and OrderPickup. NB: In a more realistic model, the order queue in the kitchen would be served by several kitchen staff members in parallel, such that they represent the resources of the OrderPreparation activity.

►Conceptual Model ^?

Conceptual Information Model ^?

There are three order processing activities: the order taking, the order preparation and the order pickup, all of which are performed by business units that have queues: the menu board for order taking, the kitchen for order preparation and the pickup window for picking up orders.

The potentially relevant object types are:

customers,
business units: menu board, kitchen, pickup window
service personnel: order taker, cook, pickup window staff

Potentially relevant types of events are:

customer arrivals,
customers queuing up at the order window,
order taking,
order preparation,
customers queuing up at the pickup window,
order pickups,
customer departures.

Notice that order taking, order preparations and order pickups are activities, which consist of a start and an end event.

Conceptual Process Model ^?

Event rules.
ON (event type)	DO (event routine)
customer arrival	If the order window is busy, then the newly arrived customer queues up, else a new order taking activity for this customer starts.
end of order taking activity	If the pickup window is busy, then the customer queues up, else a new order pickup activity for this customer starts. If there are still customers waiting in the menu board queue, the next order taking activity starts.
end of pickup activity	The served customer departs. If there are still customers waiting in the pickup window queue, the next pickup activity starts.

►Simulation Design Model ^?

Information Design Model ^?

A computational design for the purpose of computing the two statistics maximum queue length and utilization is obtained by modeling the following types of objects, events and activities:

Four object types:
1. MenuBoard with a (multi-valued) reference property waitingCustomers representing its queue, and two reference properties kitchen and pickupWindow for enabling the menu board to access the queues of the kitchen and the pickup window.
2. Kitchen with a (multi-valued) reference property waitingOrders representing its queue, a multi-valued reference property preparedOrders representing the set of prepared orders and a reference property menuBoard for enabling the kitchen to access the queue of the menu board.
3. PickupWindow with two multi-valued reference properties waitingCustomers representing its queue and preparedOrders representing the set of prepared orders, and a reference property menuBoard for enabling the kitchen to access the queue of the menu board.
4. Customer with an attribute arrivalTime for recording the customer's arrival time such that the time in system can be computed.
One event type: CustomerArrival with a reference property orderWindow having the class OrderWindow as range. As an exogenous event type, CustomerArrival has a recurrence function representing a random variable for computing the time in-between two subsequent event occurrences.
Three activity types:
1. OrderTaking has a resource association with the object type MenuBoard and a randomDuration function.
2. OrderPreparation has a resource association with Kitchen and a randomDuration function.
3. OrderPickup has a resource association with PickupWindow and a randomDuration function.

For all activity types the simulator computes the utilization of their resources.

Process Design Model ^?

Event rule design table.
ON (event type)	DO (event routine)
CustomerArrival( ow) @ t	INCREMENT ow.queueLength IF ow.queueLength = 1 THEN SCHEDULE ActivityStart("OrderTaking", ow) @ (t+1)
ActivityEnd("OrderTaking", a) @ t	SET cust = POP( a.orderWindow.waitingCustomers) SET ordPrepDuration = OrderPreparationEnd.randomDuration() SET pickupWindowQueue = a.orderWindow.pickupWindow.waitingCustomers SCHEDULE OrderPreparationEnd( cust.orderNo) @ (t + ordPrepDuration) PUSH cust TO pickupWindowQueue IF pickupWindowQueue.size = 1 THEN SCHEDULE ActivityStart("OrderPickup", a.orderWindow.pickupWindow) @ (t+1) IF a.orderWindow.waitingCustomers.size > 0 THEN SCHEDULE ActivityStart("OrderTaking", a.orderWindow) @ (t+1)
ActivityEnd("OrderPreparation", a) @ t	SET pickupWindow = a.kitchen.pickupWindow SET orderNo = POP( a.kitchen.waitingOrders) pickupWindow.preparedOrders.add( ordNo) PUSH orderNo TO pickupWindow.preparedOrders
ActivityEnd("OrderPickup", a) @ t	SET cust = POP( a.pickupWindow.waitingCustomers) IF a.pickupWindow.waitingCustomers.size > 0 THEN SCHEDULE ActivityStart("OrderPickup", a.pickupWindow) @ (t+1)

Drive Through Restaurant Back to simulation

System Narrative

Model Description

►Conceptual Model ?

Conceptual Information Model ?

Conceptual Process Model ?

►Simulation Design Model ?

Information Design Model ?

Process Design Model ?