Truck Factor / Bus Factor
Updated 2026-08-01
INTRODUCTION
English translation pending.
CORE DEFINITION
A risk metric from software engineering that counts how many people would have to become unavailable before a project can no longer continue. The name varies by country, with bus factor common in the United States and truck factor or lottery factor used elsewhere. The metric measures concentration of critical knowledge rather than team size, and a value of one signals a single point of failure in human form. It applies to code ownership, customer relationships, and any capability that lives in one person's head.
SCAFFOLDING EFFECT
Reduce cognitive load
- Dependency scan: count how many people hold knowledge the project cannot run without. - Single-point alert: treat a factor of one as an active defect, not an acceptable state. - Redundancy plan: rotate roles, pair on critical work, and write down what only one person knows.
Anchor fast decisions
Project continuity depends on the minimum number of removals that would halt it, so risk concentrates wherever knowledge is held by few people. Unlike a server, a person cannot be backed up without transferring the knowledge first, and informal knowledge stays invisible until the person leaves. Reducing the factor requires deliberate duplication of understanding, not just storing the artifacts.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Bus_factorverified
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