The local Department of Motor Vehicles office (DMV) is designed so that people e
ID: 392895 • Letter: T
Question
The local Department of Motor Vehicles office (DMV) is designed so that people enter the office and go to a reception desk to retrieve a ticket number for service. There are two different services available, permit test and photo license. On average 85 people per hour enter the DMV and approximately 85% of the people renew licenses and 15% are there to take a permit test. The process flow diagram is below:
Assume a stable process and use the information above to determine the following:
1. How long does the average person wait in the buffer “Wait for Ticket”?
2. How many people are in the activity “Get Ticket”?
3. How long does the average person wait in the buffer “Wait for Permit Agent”?
4. How long does the average person wait in the buffer “Wait for License Agent”?
5. How long does the average person coming to renew a license spend in the DMV from the time they enter, to the time they leave?
6. How long does the average person coming to take a permit test spend in the DMV from the time they enter, to the time they leave?
7. How many people on average are in the activity of Take Permit Tests?
8. What is the average number of people in the DMV?
9. What is the average time for an average person to get through the DMV?
10.What is the Flow Unit?
Wait for Permit Agent 4 people Take Permit Test 40 min. 85 people/hr 15% 85% Wait for Ticket 3 people Get Ticket min Wait for License Agent 12 people Renew License 18 min.Explanation / Answer
(1)
WIP = 3 people
Throughput rate, TH = 85 per hour
From Little's Law, Flow time (i.e. the waiting time) = WIP / TH = 3 / 85 hours = 3*60/85 minutes = 2.12 minutes.
(2)
Flow time, FT = 1 minutes
Throughput rate, TH = 85 per hour = 85/60 per minute
From Little's Law, WIP = FT x TH = 1 x 85 / 60 = 1.42 people.
(3)
WIP = 4
TH = 15% of 85 = 12.75 per hour
Flow time (i.e. the waiting time) = WIP / TH = 4 *60 / 12.75 minutes = 18.82 minutes
(4)
WIP = 12
TH = 85% of 85 = 72.25 per hour
Flow time (i.e. the waiting time) = WIP / TH = 12 *60 / 72.25 minutes = 9.97 minutes
(5)
For 'Take permit test', FT = 40 minuties
Total Flow time in the entire system = FTwait for ticket + FTget ticket + FTwait for permit agent + FTtake permit test = 2.12 + 1 + 18.82 + 40 = 61.94 minutes
(6)
For 'Renew license', FT = 18 minutes
Total Flow time in the entire system = FTwait for ticket + FTget ticket + FTwait for license agent + FTrenew license = 2.12 + 1 + 9.97 + 18 = 31.09 minutes
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