Question

The local driver’s license center processes applications for driver’s license renewals through the following three steps. First, the customer registers with the receptionist, who updates the customer’s information in the database. This first step takes 3 minutes per customer. Then, the customer visits one of 1 cashiers to pay the associated fees for the license renewal. This takes 3 minutes per customer because several forms must be printed from the computer and signed by the customer. Finally, the customer visits one of 3 license processing stations where the customer’s picture is taken and the license is printed. This final step takes 12 minutes per customer.

A) Assuming limited demand, what is the flow rate of the process in customers per hour?

B) If Demand is 6 customers per hour, what is the utilization of the receptionist?

C) If Demand is 6 customers per hour, what is the cycle time (minutes) of the process?

D) If the system starts empty and operates worker paced, how long does it take to complete the processing of 8 customers?

E) Assuming unlimited Demand, what would the new flow rate be if the center added one server to the bottleneck resource?

Answer 1

Step	Description	# workers (N)	Processing time in minutes (P)	Capacity per hour = 60*N/P
1	Reception	1	3	20
2	Cash counter	1	3	20
3	License process	3	12	15

The capacity of the system = Min(20, 20, 15) = 15 customers per hr.

A)

If the demand is unlimited, Flow rate = Capacity = 15 customers per hour

B)

Demand = 6 customers per hr.

Flow rate = Min(Capacity, Demand) = Min(15, 6) = 6 per hr.

Utilization of the receptionist = Flow rate / Capacity of the receptionist = 6 / 20 = 30%

C)

Flow rate = Min(Capacity, Demand) = Min(15, 6) = 6 per hr.

Cycle time = 1 / Flow rate = (1/6) hours = 10 minutes

D)

Assuming unlimited demand,

Flow rate = 15 per hour

The first customer will take 3+3+12 = 18 minutes

The next 7 customers will flow according to the flow rate i.e. they take 7/15 hours = 28 minutes

So, total time required to service 8 customers = 18+28 = 46 minutes

E)

Step	Description	# workers (N)	Processing time in minutes (P)	Capacity per hour = 60*N/P
1	Reception	1	3	20
2	Cash counter	1	3	20
3	License process	3+1=4	12	20

The capacity of the system = Min(20, 20, 20) = 20 customers per hr.

If the demand is unlimited, Flow rate = Capacity = 20 customers per hour