The Bus Factor in Your Company: When Knowledge Lives in Only One Head

Many companies have workflows that depend on a single person, and in daily work it sounds quite familiar: "Ms. Berger handles that." The bus factor puts a number on this observation. It asks how many employees would have to drop out at the same time before a critical process stalls, and if the answer is "one," it stands at 1.

This article explains where the term comes from, how to calculate the bus factor for your core processes with a simple matrix, how to spot knowledge monopolies in everyday work and what knowledge loss really costs. The last part is about how you and your team can spread the knowledge across more heads.

What Is the Bus Factor?

The bus factor is the number of people who would have to drop out at the same time before a process or project can no longer continue. It is also called the truck number or truck factor - same idea, different vehicle.

The term comes from software development. Developers have long been asking: how many people can a project afford to lose at most (the "bus" being the drastic metaphor for it) before nobody understands the code anymore? A project with a bus factor of 1 hangs on a single person. If that person is gone, everything stops.

Software teams responded with code reviews, pair programming, and mandatory documentation, because experience had shown them how much can depend on individual people.

Small and midsize businesses have a bus factor too, it is just named less often. Instead of code, it's about processes: Who knows how to fill out the customs paperwork for the Switzerland shipment? Who knows the password for the main supplier's portal? Who knows why the invoice for the Müller account always has to be adjusted manually before it goes out?

In a software team, the code at least lives in a repository. In an SMB, process knowledge often sits in people's heads, in email inboxes used as filing systems, and in workflows that run smoothly on a word across the hallway, as long as the right person is sitting at the right desk.

Calculating the Bus Factor: A Matrix for Your Core Processes

You can count the bus factor instead of guessing it. Per process: bus factor = the number of people who can run the process end to end without asking anyone, in the real system, with real data, including the special cases. Someone who can only do it with instructions or a phone call to a colleague doesn't count, but is the obvious candidate for the deputy role.

The bus factor of your company (or of one department) is then the lowest value among the business-critical processes. A chain is only as strong as its weakest link: ten processes with a bus factor of 3 offer little security if the eleventh, customs handling, hangs on one name.

Which processes to look at in the first place is what a process map shows you. To start, the ten to fifteen workflows without which no order ships and no invoice gets paid are enough. You can copy this template directly:

How to fill it in:

1. List the processes. Describe them specifically enough that everyone knows what is meant, so "Customs handling, Switzerland" rather than "Shipping."
2. Rate how critical each one is. High means: if the process stops for two weeks, real damage follows in revenue, deadlines, customers or liability.
3. Collect the names from the people doing the work. The manager knows part of the answer, the people running the process know the rest. Ask them: "Who can do this while you're away for three weeks, without calling you?"
4. Count the bus factor and note the absence risk of the people named.
5. Sort: a bus factor of 1 on a highly critical process with a foreseeable absence goes to the very top.

The matrix only counts whether someone runs a process independently. If you want finer levels, from "knows the process" to "can train others", extend it into a skills matrix.

Worked Example: A Wholesaler With 40 Employees

A composite example with made-up names: a plumbing supplies wholesaler takes on six core processes. One hour with the team leads is enough, followed by a short check with each person named.

The result: the company's bus factor is 1, even though most processes are well covered. The order follows from the table: customs handling first (critical, bus factor 1, departure foreseeable), then month-end prep, price maintenance after that. The matrix also shows that Ms. Berger appears in three rows, so when she retires, supplier complaints drop to a bus factor of 1 as well.

Two tips from practice: count strictly and include only people who have actually run the process themselves, because "Schulz could probably do that too" is a guess. And review the matrix twice a year, before the summer holidays, for instance, when it becomes clear anyway whose vacation cover plan holds up.

How to Spot Knowledge Monopolies in Everyday Work

Knowledge monopolies are easy to recognize in everyday work once you pay attention to a few typical signals.

"Only Ms. X knows that"

If this sentence comes up regularly in your company, you already have a map of your knowledge monopolies. For one week, write down every topic where people point to a single person, and you will have a good first list for the matrix.

Vacation coverage fails

Ms. Berger is away for two weeks. Officially, Mr. Schulz is covering for her. In practice, the work piles up on her desk, because Mr. Schulz carries the title of "backup" but has neither the access rights nor the detailed knowledge. After her vacation, Ms. Berger spends three weeks working through the backlog. When work sits still during a vacation instead of moving forward, the cause usually lies in knowledge that only one person holds so far.

The resignation shock

An employee resigns, and the leadership team mainly wonders what knowledge will leave with him. The remaining weeks of the notice period become the handover, in which the departing colleague is supposed to capture in four weeks what he built up over fourteen years. That only partly works, because much of it is so self-evident to him that he no longer sees it as knowledge. What is still realistically doable in that situation is covered in the guide on knowledge transfer when employees leave.

More signals you should take seriously

• New hires need a long time to get up to speed, because they mostly sit next to a colleague and watch. A structured onboarding plan quickly shows which stations depend on a single person.
• The process manual dates from 2021 and was created for a certification. The workflows have evolved since then, while the manual has stayed at that earlier state.
• With certain people, nobody can imagine how things would continue without them, because their knowledge exists nowhere else.
• Questions always route through the same people. Anyone who gets interrupted constantly because "only he knows that" holds a knowledge monopoly and becomes a bottleneck for everyone else.

What Knowledge Loss Really Costs

There are no credible blanket figures here, and studies claiming "knowledge loss costs X euros per employee" are best read with caution. You can, however, run the numbers for your own company quite well yourself. The costs come from four line items:

1. Rebuilding the knowledge. When knowledge leaves with a person, it has to be rebuilt from scratch. The successor experiments, makes mistakes, asks suppliers and customers things that were settled internally long ago. Do the sober math: how many months does a successor need to reach the predecessor's level? For specialized knowledge, that is often several months, during which the full salary runs while output only grows gradually.

2. The mistakes in the meantime. The incorrectly filled-out customs declaration, the missed deadline on the framework agreement, the customer whose special terms nobody remembered. A single one of these mistakes can be expensive, and they happen precisely during the time when the knowledge that would have prevented them is missing.

3. The everyday bottleneck. Knowledge monopolies cost something every day, even without a resignation: decisions wait until the one person has time, projects slip because a single calendar sets the pace, and the knowledge holders themselves barely get to their actual work because of all the questions.

4. The dependency. Someone who is irreplaceable negotiates differently. That's human, and the people involved are often not even aware of it, yet a company that depends on individual heads has less room to move in salary negotiations, during change, and in conflicts.

The exact amount differs from company to company. Often, knowledge lost to a resignation turns out more expensive than prevention would have been. Often the most expensive share of it is tacit knowledge: the rules of thumb that appear in no file.

Raising the Bus Factor: Breaking Up Knowledge Silos in Brief

If you want to raise the bus factor, a focused approach takes you further than the resolution to document everything at once. It fits into four points:

• Make the situation visible. The matrix above is the first step. The org chart adds the positions, while the matrix shows where the knowledge sits.
• Prioritize by risk. A critical process whose knowledge holder is likely to leave comes first.
• Spread the knowledge across more heads, with real deputy arrangements in which the backup runs the process themselves. Which handover formats work is compared in the guide on knowledge transfer methods.
• Keep the documentation alive. Living process documentation or a knowledge base stays current when it has a named owner and fixed update triggers.

The full guide with five strategies, typical mistakes and success criteria is Knowledge Silos: 5 Strategies to Break Them Up. One piece of advice up front: start small, with one department, its five most critical processes and the two biggest knowledge monopolies. One dismantled monopoly helps you more in daily work than a concept covering everything. How these individual steps fit together into a lasting system is covered in the guide on implementing knowledge management.

Making it visible is where tools like wissa.ai come in: an AI conducts short interviews with your employees, around 15 to 20 minutes per conversation, via chat and whenever it suits them. If someone says "Max and Hanne handle the complaints," the AI suggests inviting both next, and the invitation goes out once you approve it. The system works its way from one knowledge holder to the next and flags as a knowledge risk which workflows, according to the interviews, only one person describes, each with the underlying statements as evidence. That gives you a good basis for filling in your bus factor matrix.

Conclusion: The Bus Rarely Comes, Change Always Does

Thankfully, the bus from the metaphor almost never actually hits anyone. Employees do resign, retire, fall ill, or move into different roles, though, and every company experiences this sooner or later. If you are prepared, the knowledge stays in the company when the time comes. One hour with the matrix shows you where you stand today.

If you would like to see where your knowledge monopolies sit, each person can describe their work in a short AI interview, with hosting in Germany and AI processing in the EU. You can start right after sign-up, and a free trial package to start with (10 credits, once per company, terms) usually covers a first interview. Try one interview for free

FAQ

What does a bus factor of 1 mean?

A bus factor of 1 means the loss of a single person paralyzes a process or an entire project, because only that person has the necessary knowledge. The higher the bus factor, the more people would have to drop out at the same time before things get critical. The target for every business-critical process: a bus factor of at least 2.

How do you calculate the bus factor?

For each process, count the people who can run it end to end without asking anyone - that is its bus factor. Someone who can only do it with instructions doesn't count. The company's bus factor is the lowest value among the business-critical processes. In practice, a matrix does the job: core processes in the rows, plus criticality, names, bus factor, absence risk and next step.

What is the difference between bus factor and truck number?

The terms mean the same thing. Truck number and truck factor are synonyms for the bus factor. All three terms describe the number of people who would have to drop out before a process or project stalls.

How do I find out where knowledge monopolies exist in my company?

Listen for sentences like "only Ms. X knows that," check which topics sit still while individual people are on vacation, and ask the employees themselves as well as the management level. The systematic way is structured interviews with everyone involved, from which you can read off which processes hang on exactly one name.

Isn't a handover from departing employees enough?

A handover helps, but in the final weeks of a notice period it can only capture part of the knowledge that grew over many years, because much of it has become second nature to the departing colleague. Securing knowledge works best while the person is still working in the company calmly and without the pressure of leaving.

What does knowledge loss cost when someone resigns?

There is no credible blanket figure. Run the numbers for your own case: months until the successor reaches full productivity, mistakes and missed deadlines during the transition, projects left sitting. With specialized knowledge, the total can add up considerably, and prevention is often the cheaper option.

Don't knowledge holders resist sharing their knowledge?

Sometimes, but often something else is behind it: many knowledge monopolies arise from lack of time, because in daily work nobody ever asked. Many knowledge holders are relieved when they no longer have to answer every question themselves and can take a vacation without worrying. What matters is the framing: voluntary participation, a respectful conversation and no assessment of individual performance or behavior.

Sources

• ISO 9001:2015, clause 7.1.6 "Organizational knowledge": the organization shall determine the knowledge necessary for the operation of its processes, maintain it and make it available.
• ISO 9001:2015, Annex A.7: explicitly names safeguarding the organization from loss of knowledge, for example through staff turnover or failure to capture and share information.