Definition
Bus Factor
Bus factor is the number of people who would have to leave a project before it stalls for lack of knowledge. A low bus factor signals dangerous knowledge concentration. The raw number is only meaningful with team size as context.
What bus factor measures
Bus factor, sometimes called truck factor, is a risk measure. It asks a blunt question: how many people would have to be hit by a bus, or more realistically quit, before a project loses the knowledge it needs to keep moving. A bus factor of one means a single person holds critical knowledge nobody else has.
The lower the number, the higher the risk. It is a measure of how concentrated knowledge and ownership are across the people who do the work.
How to measure it
The signal lives in git history. Look at who authors and reviews the code in each area of the codebase. When a single contributor accounts for the large majority of changes to a critical module, and no one else reviews it, that module has a bus factor of one.
File ownership concentration, review participation, and the spread of commits across contributors all feed the estimate. The output is per area, not a single global number, because risk is local: one service can be dangerously concentrated while the rest of the codebase is well shared.
Where the raw number misleads
Bus factor is only meaningful with team size as context. A solo founder has a bus factor of one on everything, by definition. That is not a finding, it is a tautology. Reporting it as a critical risk is noise.
A useful bus-factor signal compares concentration against the number of people who could realistically share the load. The question is not "is this owned by one person" but "is this owned by one person when it should not be." Without that context, the metric generates alarms a leader cannot act on.
How InteliG uses it
InteliG resolves contributors into one identity per person first, so bots and duplicate logins do not distort ownership. It then reads file ownership and review patterns against the actual size of the team, so bus-factor risk surfaces where it is real and stays quiet where it is structural. The result points at the modules worth de-risking, not every place one person happens to work.
Related terms
- Execution Intelligence — reading risk in the context of how the whole organization executes
- Atomic Code Linking — the attribution that makes ownership measurable per contributor