Touch Time vs. Lead Time: How to Find the Optimal Workflow Control
Flow Theory of Constraints
Touch Time vs. Lead Time: How to Find the Optimal Workflow Control
July 27, 2025
Wolfram Müller - 2024-07-27 - CC-BY-SA
Last week, someone challenged me. He said, "You talk a lot about touch time and lead time. But honestly... I don't get it. What's the point?"
Fair question. And I must admit, it got under my skin a little. Not because he questioned the idea, but because he was right. I hadn't explained it well. In practice, this concept works beautifully. But if people can't understand it, it's useless.
That night, I sat down to figure it out. What's really behind this "touch time vs. lead time" thing? How can I make it clearer?
What Is Touch Time vs. Lead Time, and Why Does It Matter?
Let's start simple.
- Touch Time is the actual time someone is working on a task.
- Lead Time is the full time from when the task, order, or project is started to when it's delivered. That includes waiting, delays, handovers, etc.
To make it even clearer:
For this article, I want to be even more specific. I talk about the Execution Lead Time - this is the internal view of the lead time. A task, order, or project may have to wait in a queue to ensure that the constraint is not overloaded. I call this Queue Waiting Time.
Then the task, order, or project starts, and the Execution Lead Time begins. During execution, you cannot always work on the task, order, or project, so the Touch Time is shorter than the Execution Lead Time.
From the customer's perspective, the lead time is:
Queue Waiting Time + Execution Lead Time
In the following, I use "Lead Time" to mean "Execution Lead Time."
The ratio between these two is touch time divided by lead time. It's a powerful indicator of the characteristics of your workflow and which workflow-control approach is best.
For example:
- If your ratio is under 10%, you're typically in a production environment.
- If it's over 20%, you're getting into project territory.
And all current agile methods are based on production controls - just a side note.
Sounds clean, right? But here's where the confusion starts...
Wait... What If Agile Teams Show High Touch-Time/Lead-Time Ratios?
That was the second challenge I got. Someone said, "But in Agile, we often focus hard on one story at a time. That means our touch time and lead time are almost the same. So aren't we near 100%?" And I had to admit - they had a point.
The same applies to projects: when a project sits in a backlog for months before starting, its ratio drops.
So is it really a production or project issue?
It turns out that we're missing a key variable.
The Hidden Ingredient: Do You Have a Due Date?
Here's what I'd overlooked for years because it felt so obvious: This entire discussion only makes sense when due dates exist.
If you don't have a due date - if no one is waiting for something by a specific time - then the touch-time/lead-time ratio doesn't matter. You're free to use whichever workflow-management approach you want, provided that you work with focus.
But in the real world, most organizations do have due dates:
- Customers want something by a certain time.
- You're preparing for a trade show.
- You're aiming to beat a competitor to market.
- Even "ASAP" is a due date in disguise.
So the first big question is:
👉 Do you have due dates?
If yes, the ratio tells you a lot, and things get interesting.
If not, be happy!
Simply select the items that promise the highest value with the shortest lead time, focus on them, and be happy!
What If You Don't Have a Due Date? Are You Truly Free?
Let's say you're working on a product or innovation, and you can "release when ready." No deadline. Sounds great.
But here's the next question:
👉 Are you truly autonomous? And be honest!
- Do you share people or suppliers with other teams?
- Are you dependent on a shared company budget or shared funding?
- Is your profitability compared with that of other products?
- Do you compete for decision-making capacity?
If you answered "yes" to any of these, then you're not fully free.
You're coupled with others. And where there's coupling, there's usually...
👉 A constraint.
Why Constraints Automatically Create Due Dates
When multiple teams depend on the same resource - whether it is a person, a supplier, decision-making capacity, or a budget - a queue forms. You have to wait for your turn.
Even if no external deadline exists, the constraint creates a de facto due date. Your place in the queue determines your start time and finish time - and therefore your due date.
Suddenly, you're not in the "release when ready" world anymore. You're back in the world of due dates, even if you created them yourself through prioritization.
Now That You Have a Due Date - What's the Right Control Method?
Once you're in the due-date world, you can start thinking intelligently about how to control work.
Here's where the touch-time/lead-time ratio comes back in:
- If your touch-time/lead-time ratio is below 10%, you're in a production-style flow. Use controls such as Drum-Buffer-Rope (DBR) or one of its variations: simplified Drum-Buffer-Rope (sDBR), or even super-simplified DBR. These approaches are simple, low-overhead, and highly effective.
- If you're above 20%, welcome to project management. You'll need tools such as Critical Chain Project Management (CCPM) or an agile approach at the team level with a project-level critical chain on top - agile CCPM, also known as aCCPM.
- If you're between 10% and 20%, you're in a mixed zone. A hybrid approach might fit best: DBR with a lightweight buffer system that is monitored closely.
A simple rule of thumb:
👉 The lower the touch-time/lead-time ratio, the more production-like the control. The higher the touch-time/lead-time ratio, the more project-like the control.
So What About Scrum and Kanban? Where Do They Fit In?
Great question. Scrum and Kanban are early-generation production-control methods. They work well in stable contexts, but they're often too weak for flow optimization when the system becomes larger, more coupled, or more dynamic.
Drum-Buffer-Rope, from the Theory of Constraints, is a third-generation production-control method. It enables less work in progress and is much more flexible. It is stronger - especially when you want lead-time reliability, not just "velocity" or "throughput."
Overview of the full decision tree...
Back to the Beginning: Did We Solve the Riddle?
Let's revisit the challenges:
- Can Agile have a near-100% touch-time/lead-time ratio? ✅ Yes - but only in rare, fully autonomous teams with no due dates or constraints. That is not the norm at all. If you look more broadly or assess the situation honestly, you are very seldom fully autonomous.
- Can projects have a low touch-time/lead-time ratio? ✅ Yes - with waiting times before they start. Once they're active, they should run quickly and with full focus. However, long waiting times should not be the norm in multi-project environments. You should take action to make better use of the constraint or add capacity so that the waiting times disappear. Waiting times before a project starts are therefore also a sign that the constraint requires attention.
- When is the touch-time/lead-time ratio meaningful? ✅ When due dates - external or constraint-driven - are involved. I assume that this applies in 99% of cases!
And now, you know what to do with it.
Final Question: Do You Know Your Ratio?
If you're leading a team, a product, or a portfolio, start by checking your touch time vs. lead time. Then ask:
- Do we have due dates?
- Are we truly autonomous?
- If not, what's our constraint? How do we determine priorities and due dates?
- Based on the ratio, are we running projects or running production?
Get those answers right, and you'll find that the optimal workflow control almost takes care of itself.
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