Hello TOC

TOC in Project Management · Lesson 3 of 6

WIP control

The number of projects open at once decides how much the whole system delivers. Too few starves people; too many drowns them. Find the middle and hold it.

12 min · Not completed yet

Getting out of the vicious loop

If too many open projects cause bad multitasking, the obvious question is: how many should be open?

Plot the number of projects active in the system against what the system delivers, and you get an inverted parabola:

  • Too few projects: the zone of starvation. Resources sit idle waiting for work.
  • Too many: the zone of bad multitasking. Resources are stretched, tasks take longer, issues wait to be resolved, expediting is constant and rework grows. Output falls as more is started.

Most organisations live far to the right of the peak, and they push further right every time they start another urgent project.

Pause and think: a team is in the zone of bad multitasking. Management wants more output. What happens if they start two more projects?

  • Output falls further, and every project slows down
  • Output rises, because there is more to work on
  • Nothing changes
  • Only the new projects slow down

To the right of the peak, every extra project adds switching and waiting for everyone. The way to more output is to open fewer projects, not more.

How WIP control works

  1. Make a bank of all projects waiting to be worked on.
  2. Give each one a unique, fixed priority: 1, 2, 3, 4… No ties, no “all top priority”, and no re-ranking every week because someone shouted.
  3. Deploy only the top few, as many as the team can work on without multitasking. The rest wait.
  4. One out, one in. A new project starts only when an active one finishes.

It feels risky to let projects wait. But a waiting project isn’t losing anything: under multitasking it would have been crawling anyway. With fewer open, each one moves fast, finishes sooner, and the waiting ones start earlier than you’d expect.

Yes, but…

WIP control releases a lot of capacity, but it doesn’t fix everything. Even with few projects open, starting a phase of work without complete preparation, such as missing drawings, an unapproved spec or a contractor not yet hired, causes interruptions and rework in the middle of execution. That’s the next lesson.

Check your understanding

Answer all five. Get four right to complete the lesson.

1. Plotting projects open against system output gives…

  • A straight rising line
  • A flat line
  • A falling line
  • An inverted parabola

Output rises, peaks, then falls as multitasking takes over.

2. Many idle resources is a sign of…

  • Bad multitasking
  • The zone of starvation
  • Perfect balance
  • Too many projects

Too few projects open for the team.

3. In WIP control, project priorities should be…

  • Re-ranked every week
  • All equal
  • Unique and fixed
  • Set by whoever escalates

A clear, stable sequence is what lets people stop switching.

4. “One out, one in” means…

  • A new project starts only when an active one finishes
  • One person leaves for every hire
  • One task per day
  • One project per customer

That rule keeps WIP at its limit.

5. What problem remains even with good WIP control?

  • Too many idle people
  • No priorities
  • Too few projects
  • Work started without complete preparation still causes interruptions and rework

That’s what full kit addresses.