Why managing queues is a key to accelerating your product development process. What are the causes of queues and how to reduce batch size to learn as well as launch earlier.

1. This work is licensed under a Creative Commons Attribution-NoDerivs 3.0 Unported License.
Queues and Batches
PLAYBOOK LEAN PRODUCT DEVELOPMENT SERIES
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2. PLAYBOOK LEAN PRODUCT DEVELOPMENT SERIES
This series is for anyone interested in Lean, Agile and team principles
and how they can be applied in new product development scenarios
to increase innovation, improve delivery times and create engaged,
happy, high-performing teams.
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3. Notes:
1. A queue is where the flow of anything stops to wait for something else to happen.
a. People waiting in line at the grocery store.
b. ECOs in an Approver’s inbox.
c. Parts waiting for inspection.
2. What examples did you think of?
a. ____________________________________________________
b. ____________________________________________________
c. ____________________________________________________
d. ____________________________________________________
3. There are many examples throughout product development.

4. Notes:
1. The majority of New Product Development time is spent in _______________.
2. Queue Time is typically _______________ than Server Time.
a. Does the image shown in the slide make sense?
b. Do you believe it?
c. Examples:
i.
ECOs sit in someone’s inbox waiting to be reviewed and signed.
ii. Information waits in someone’s head waiting to be shared with someone
that needs it.
3. What would happen if all of the top-priority project’s tasks were processed
immediately?
___________________________________________________________________.
4. The perceived problem is that every other project in the system would get
_______________. Is this really a problem?
a. Is it bad to delay a lower priority project in order to speed up a higher priority
project?
b. Where is the highest cost of delay? How will you make the most money?
c. What is the alternative?
5. Queues can be managed in ways that will speed up execution of all projects.
6. In order to better manage queues, you need to understand what creates them.

5. Notes:
1. In this example Arrival Rate = 2 items/unit time and Departure Rate = 1 item/unit
time.
2. Let’s say the items are Engineering drawings entering into Document Control for
release and the unit of time is days.
3. After 10 days, how many drawings will there be in the queue (i.e. WIP inventory)?
________.
4. Assuming nothing changes, how long would you expect to wait for Document Control
to release the drawings in the queue on Day 10 (i.e. Cycle Time)?
__________________.
5. What makes this queue go away?
______________________________________________.

6. Notes:
1. The first source of queues is when the system is _______________.
a. Too many shoppers in line at the grocery store.
b. Too many ECOs in Document Control’s or an Approver’s inbox.
2. System loading relates to how much the resources are utilized.
3. Capacity Utilization has a non-linear effect on cycle time.
a. Non-linear indicates a _______________ point.
b. Small changes can have a big impact (positive or negative).
4. When the arrival rate consistently exceeds the processing rate, a _______________
will form and never go away, and the system will be at 100% utilization forever.

7. Notes:
1. As the system becomes more loaded, it takes _______________ to get through it.
2. The image above shows the non-linear effect of capacity utilization on duration.
a. Wherever you are on the curve, go halfway to 100% and you
_______________ cycle time.
b. Increase utilization from 60% to 80% and double the time it takes to get
through the system.
c. Increase utilization from 80% to 90% and double it again.
d. Notice how quickly cycle time rises at high levels of capacity utilization.
e. What percent capacity utilization do you think Product Development is at?
_________.
3. The roads and highways are a good analogy…
a. At rush hour a highway is at high utilization.
b. By blocking 1 lane of 4, we further increase the “loading” of the remaining 3
lanes by 33%.
c. How far does a 33% increase move you if you were initially at 20% loaded?
_________.
d. How far does a 33% increase move you if you were initially at 75% loaded?
_________.
e. What’s the relative difference in the cycle time of the system in each case?
______________ and ______________.

8. Notes (continued):
4. Duration = Work/Availability
a. How long something takes (Duration) is determined by how much work is
involved (Work) and how much time you have to perform that work
(Availability).
b. The more utilized you are, the less available you are, and therefore it will take
longer.
5. What happens to Duration as Availability goes to 0?_______________.
6. This is one of the keys to Lean Product Development…
a. _______________ is more Profitable than Efficiency!
b. If you want to get projects done faster and be more profitable, keep resource
utilization low!
c. The increase in profit from faster projects more than pays for the extra
capacity.
d. You cannot make more profit by working on more things!
e. Everything takes longer!

9. Notes:
1. Variability has many impacts on queues.
2. Variability can be from…
a. ________________ rate
b. ________________ time
3. Product development has a lot of variability….
a. How long will it take to determine a requirement?
b. How long will it take to complete a design?
c. How long will it take to troubleshoot a circuit board?
4. Variability makes it more difficult to optimize a system.
5. Techniques for reducing variability include…
a. _______________ processes
b. _______________ designs
c. _______________ tools and processes
d. _______________ batch sizes
6. Variability causes the Capacity Utilization curve to rise sooner, which means you
have to run the system with even more spare _______________.
7. Not all variability is bad… you can’t create new and innovative products without
variability…
8. What are examples of bad variability? _______________.

10. Notes:
9. There’s uncertainty in the amount of Work. How accurate do you think your Work
estimates are (plus or minus %)?
10.There’s uncertainty in your Availability. How certain are you in your Availability (plus
or minus%)?

11. Notes:
1. One source of variability AND queues are large batches. Examples:
a. Baking cookies.
b. A long line of cars trying to enter the highway.
c. A large number of drawings on one ECO.
2. A batch can load that part of the system to _______________ utilization.
a. The system will remain overloaded until the batch has been completely
processed.
b. Any hiccups (i.e. additional variability) can cause major slowdowns.
c. This will result in batches piling up into a _______________ queue state which
takes a long time to clear.
3. The positive effect of small batch size is one of the reasons for the metering lights at
highway on-ramps.
4. Items in a batch typically spend time in two queues.
a. Inbox queue
Example: for ECOs with multiple drawings, all drawings except the first have
to wait while the first one is being reviewed by the approver.
b. Outbox queue
Example: for ECOs with multiple drawings, once the first drawing has been
completed, it must wait for all of the others to be completed .
5. And every queue ____________ the flow! And time is again wasted waiting in line.
6. One piece flow is the ultimate goal of Lean Manufacturing. In Product Development
easy to use tools and systems that utilize smaller batch sizes must be developed and
implemented.

12. Notes:
1. Remember: If the arrival rate slope = 2 items/unit time and the departure rate
slope = 1 item/unit time, then after 10 units of time, how many will I have in my
queue? _______________.
2. What happens if suddenly, someone puts a large batch of work into the system?
___________________________________________________________________.

13. Notes:
1. We can manage and reduce the queues, and increase the flow (throughput) as a
result.
2. Let’s look at each of these in more detail.
a. Increase Capacity
i.
Very _______________
ii. _______________ cost
iii. The work in the system will expand to fill it unless active limits are put in
place.
b. Manage Demand
i.
This can reduce customer offerings or increase risk by eliminating tasks.
ii. Be careful not to batch to create _______________ efficiencies. They
hurt much more than they help.
c. Reduce Variability
i.
You cannot eliminate all variability and still develop _______________
new products.
ii. Variability reduction can be expensive.
d. Use Control Systems
i.
This option is very effective, but can require active management and
attention.
e. Batch size _______________ is the most effective, least cost option.

14. Notes:
1. Throttling Demand controls the cadence at which work is put into the system.
2. Highways throttle demand at times of high capacity by slowing the rate at which
vehicles can enter the highway at on-ramps using metering lights.
a. Decreases congestion and breaks up ‘platoons’ of vehicles.
i.
Platoons are groups of vehicles traveling in close proximity to each other,
such as a group released by a traffic signal changing from red to green.
ii. Platoons are an example of _______________.
b. Improves _______________ through the bottleneck prone region.
3. Work in Progress (WIP) constraints limit the amount of work in any part of the
system.
a. The total number of vehicles allowed on the highway at one time could be
limited. Once the limit is reached, on-ramp gates could be closed until a certain
number of vehicles exited the highway at which time the on-ramp gates could
re-open and allow more vehicles to enter the system.
b. Companies could limit the number of active projects in Development to a fixed
number of projects. Future projects can begin only when a previous project has
been completed (i.e. as resources are available).
c. To be effective, WIP Constraints require everyone’s discipline from Senior
Management down.

15. Notes:
1. When reorganized as shown, Projects A & B have the benefit of an early completion,
thus increasing their profit potential.
2. Projects C & D have the benefit of a late start… information learned by completing
Projects A & B is applied.

16. Notes:
Push vs. Pull Systems
1. A traditional Push system is one in which work is pushed or loaded on the resources
as soon as it exists.
2. Pushing work slows down the system as it:
a. Overloads the resources
b. Creates queues
c. Encourages multitasking
d. All of which result in higher cycle times (lower throughput).
3. In Pull systems resources pull work from a limited, small backlog of prioritized work
as they have spare capacity.
a. In order to give someone work, other work has to be completed or removed
first.
b. In this way Pull systems naturally constrain WIP
4. As a result Pull systems:
a. Don’t overload resources
b. Minimize queues
c. Don’t encourage multitasking
d. All of which result in lower cycle times (higher throughput).
5. This is one principle of Lean Manufacturing that has great benefit in Product
Development.

17. Notes (continued):
Push vs. Pull Systems
6. For Example, back to our cafeteria:
a. Even if people arrive at predefined times, lines (queues) will form due to
variability in processing time.
i. John arrived on schedule but he ordered lunch for the 4 other people in his
meeting…
OR
ii. The cash register runs out of receipt paper or needs to get change or the
credit card machine breaks down…
iii. As a result Bill arrives at his predefined time to find there’s a line and he
has to wait to place his order and get his lunch
iv. A push system lacks active monitoring of the system’s capacity and
continues to unknowingly load the system
b. In a Pull system the number of people in line at any time would be actively
monitored and demand managed
i.
A text message or other form of notification would be sent to the next
person to be served lunch when the cafeteria can handle more people
ii. This would keep lines shorter and processing times shorter

18. Overview
1.
The game represents stages of any process.
2.
Players receive a batch of items, process that batch, and pass the batch to the
next person in the process.
3.
A roll of a die will determine how much work each person gets done each day.
Setup
1.
Organize into groups of 4 players.
2.
Each group assigns each player one of the following roles:
Engineer, Document Control, Approver I, and Approver II (for groups of 3,
Approver I & Approver II are the same player).
3.
Arrange players in the following sequence:
4.
Each player has an Inbox and an Outbox.
5.
The Engineer places 30 Drawings in his Inbox, i.e. 3 stacks of 10 poker chips.
6.
Approver II plays and keeps track the of team’s progress on the Score Sheet.

19. How to Play
1.
On Day 1 the Engineer roles the die and moves the rolled amount of drawings from
his Inbox to his Outbox. On the Score Sheet Approver II notes in the Day 1 row on
the number of drawings moved.
2.
If the Engineer doesn’t have a batch of 10 drawings in his Outbox, he continues his
work on Day 2 by rolling the die and moving the rolled amount of drawings from
his Inbox to his Outbox. Approver II notes in the Day 2 row on the Score Sheet
the number of drawings moved.
3.
When the Engineer has a batch of 10 drawings in his Outbox, then, and only
then, he moves 1 stack of 10 drawings to Document Control’s Inbox.
4. On the same day Document Control rolls the die and moves the rolled amount
from his Inbox to his Outbox. Approver II notes in the appropriate Day row the
number of drawings moved.
5.
If Document Control doesn’t have a batch of 10 drawings in his Outbox, play
continues on the next day starting again with the Engineer.
Note: Each player plays, one at a time, in sequential order only, not in parallel
(i.e. No playing while others are rolling their die).
6.
When Document Control has a batch of 10 drawings, then, and only then, he
moves 1 stack of 10 drawings to Approver I’s Inbox.
7. On the same day Approver I rolls the die and moves the rolled amount from her
Inbox to her Outbox. Approver II notes the number of drawings moved.
8.
If Approver I doesn’t have a batch of 10 drawings in his Outbox, play continues on
the next day starting again with the Engineer, followed by Document Control, then
Approver I. Play continues until all 4 players are processing drawings.
9.
When Approver II has a batch of 10 drawings in his Outbox, then, and only then,
he notes it as a Completed Batch on the Score Sheet on the same day.
10. The game is over when all of 30 drawings, 3 batches of 10, have been completed.
11. Each group will play two games:
Game #1: Drawings = 30, Batch size = 10
Game #2: Drawings = 30, Batch size = 2
12. Complete Game #1 before starting Game #2.
13. Compare and contrast the games and be prepared to discuss with everyone.

22. What did you notice?
1. After Game 1 (batch size = 10)
a. How long did it take to get the 1st batch through the system?
b. How long did it take to get the last batch through the system?
c. How did you feel?
d. Let’s say there is a problem with drawing #2 that only Approver II can identify.
i.
How long did it take to find out there was a problem (i.e. how long is the
learning delayed)?
ii. How long would it take to get drawing #2 back through the process to
where you were assuming it had to go through the same process (i.e.
Engineer diagnose/correct, Document Control process, Approver I reviews,
Approver II reviews)?
e. What’s the impact of Approver II waiting to go through Approver I?
f.
What happens if either Approver only had 30 min on a day to review drawings?
2. After Game 2 (batch size = 2)
a. How long did it take to get the 1st batch and last batch through the system?
b. How long did it take to get the last batch through the system?
c. How did you feel in comparison to Game 1?
d. Let’s say there is a problem with drawing #2 that only Approver II can identify.
i.
How long did it take to find out there was a problem? How long is the
learning delayed?
ii. How long would it take to get drawing #2 back through the process to
where you were assuming it had to go through the same process (i.e.
Engineer diagnose/correct, Document Control process, Approver I reviews,
Approver II reviews)?
e. What’s the impact of Approver II waiting to go through Approver I?
f.
What happens if either Approver only had 30 min on a day to review drawings?

23. Notes:
1. Each game simulates a different approach to increasing the throughput of a system
(i.e. reducing system cycle time).
2. Use the same guidelines to play each game.
3. Print the score sheets for each and record your results.
4. Compare and contrast the games and be prepared to discuss with everyone.

27. What did you notice?
1. Increase Capacity (Batch size = 10; Add 1 to each roll to increase capacity 33%)
a. How long did it take to get the 1st batch through the system?
b. How long did it take to get the last batch through the system?
c. How did you feel? Did you feel less overloaded?
d. Let’s say there is a problem with drawing #2 that only Approver II can identify.
i.
How long did it take to find out there was a problem (i.e. how long is the learning
delayed)?
ii. How long would it take to get drawing #2 back through the process to where you
were assuming it had to go through the same process (i.e. Engineer diagnose/correct,
Document Control process, Approver I reviews, Approver II reviews)?
2. Manage Demand (Batch size = 10; #drawings reduced by 33% to 20)
a. How long did it take to get the 1st batch through the system?
b. How long did it take to get the last batch through the system?
c. How did you feel? Did you feel less overloaded?
d. The main benefit of managing demand is that you would most likely not work on one stack
of drawings at a time, instead you’ll multitask and further slow down the system.
Therefore, managing demand helps minimize multitasking.
3. Reduce Variability (All rolls ≤ 3 = 3; All rolls ≥ 4 =4)
a. How long did it take to get the 1st batch through the system?
b. How long did it take to get the last batch through the system?
c. How did you feel? Did you feel less overloaded?
d. Should this have done us any good?
e. Time Blocking promotes the same benefit (details in the Visual Work Management class).
4. Reduce Batch Size & Increase Work (Increase Work 20% to 36 drawings; Batch size = 2)
a. How long did it take to get the 1st batch through the system?
b. How long did it take to get the last batch through the system?
c. How did you feel? Did you feel less overloaded?
d. We got 20% more work done in the same amount of time (or less) than the baseline game
(Game 1).
e. Some of the added work is in the form of transaction cost, not only the drawings.
f. Was the cost of operating higher or lower than the baseline game?
5. Flexible Resources (When there are 7 or more drawings in your Inbox, roll twice. Except for the
Engineer.)
a. How long did it take to get the 1st batch through the system?
b. How long did it take to get the last batch through the system?
c. How did you feel? Did you feel less overloaded?
d. What do you need to have in place in order to be able to utilize flexible resources?
e. Was the cost of operating higher or lower than the baseline game?

28. Notes:
1. The Total Cost Curve (U-shaped) applies to ___________________ batches.
2. Cost of Delay rises with ___________________ size.
3. You don’t have to be perfect because the bottom of the total cost curve is fairly
___________________.
4. If you approach the sharp incline on the left, your total cost ___________________
dramatically.
5. Most companies are too far to the ___________________ in most areas.
6. We try to save a little ___________________ by batching things, but we lose
___________________ than we save from the delay that the batch causes.
7. Focus on reducing ___________________ and you will reduce costs
8. If you reduce costs, you increase _______________.

29. Key Takeaways
1. A queue stops the flow
– Slows the development process
– Find and reduce the queues and you will speed up
development
2. Duration varies greatly with resource availability
–
–
You lose more time when a resource’s availability goes
down than you gain back when it goes up by an
equivalent amount.
Keeping availability above 50% will ensure much more
accurate task duration estimates.
3. What’s the most effective, least expensive way
to reduce queues? Reduce Batch Sizes!
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30. THANK YOU!
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