Free tool
What breaks when people are out?
The bus factor is how many people your team can lose before something gets stuck. Tick who can handle what, see your single points of failure, then put the team on a calendar and find the days nobody who covers an area is in.
Your team's bus factor, area by area.
Rename the people and the areas, tick who can handle each one, and the bus factor updates as you go. Nothing leaves your browser.
| Who can handle… | |||||
|---|---|---|---|---|---|
| Bus factor 2 | Bus factor 1 | Bus factor 3 | Bus factor 2 |
Your team's bus factor is 1
- When Ana is out, nobody covers iOS releases.
A bus factor of 2 still breaks in December.
Two people covering payments sounds safe until both take the week between Christmas and New Year. The count tells you who can handle an area. The calendar tells you when they're actually in. This board has time off and public holidays on it, and the summary at the top names the days an area has nobody.
- Each person lists what they cover
- The summary names the first day nobody covering an area is in
- Public holidays count, per person's country
- Drag across a row to add time off and watch the gaps move
What the bus factor means, and why vacations matter more than buses.
The name comes from a grim question: how many people would have to be hit by a bus before the project stalls? Nobody plans for buses. But every team plans, or forgets to plan, for the ordinary version: vacations, sick days, parental leave, public holidays in another country, and people leaving for another job.
An area with a bus factor of 1 has a single point of failure, often shortened to SPOF. It doesn't mean the person is doing anything wrong. Usually they're the one who built the thing, and nobody else has needed to touch it. It only becomes a problem on the days they're out, which is why it's worth checking against the calendar instead of the org chart.
Three areas to check first: whatever is on call (infrastructure, payments, security), whatever has a release coming up, and whatever has a promised response time to customers. For those, aim for a bus factor of at least 2, and make sure the two people aren't out the same week. The weeks around Thanksgiving, Christmas and New Year are when that happens most. See who works between Christmas and New Year for planning that week.
How to raise it without a reorg.
Pair on the scary parts
One afternoon a sprint with someone else at the keyboard on the area only one person knows.
Rotate releases and on-call
If the same person always ships, they're the only one who can. Put a second name on the rotation.
Write the runbook
The steps someone else would need at 2 AM: where the logs are, how to roll back, who to call.
Stagger the coverers' time off
Two people who cover an area shouldn't take the same week. Check before approving the second request.
Questions
What is the bus factor?
The bus factor is the number of people who would have to be unavailable before a piece of work gets stuck. If only one person can deploy the payments service, its bus factor is 1. It's also called the truck factor or lottery factor.
What does a bus factor of 1 mean?
It means one person is a single point of failure: when they're on vacation, sick or leave the company, nobody else can handle that area. Every day that person is out, the area has no cover.
How do you calculate a team's bus factor?
List the areas your team owns and who can handle each one. An area's bus factor is how many people can handle it. The team's bus factor is the lowest of those numbers, because that's where the team breaks first.
What is a good bus factor?
At least 2 for every area that matters, and 3 for anything on call. A bus factor of 2 still fails when both people take the same week off, so check vacations and public holidays too, not just the count.
What does SPOF mean?
SPOF stands for single point of failure: one part of a system, or one person on a team, that stops everything when it fails or is away. A bus factor of 1 is a SPOF.
How do you increase the bus factor?
Pair on the risky areas, rotate who does releases and on-call, write runbooks, and make sure the two people who cover an area don't take the same weeks off. Review it before the holidays, when people are most likely to be away at the same time.