A bus factor in simple terms is the number of people who would need to get hit by a bus in order for the project to be in serious trouble.

a three quarter fish eye view of a yellow city bus

For example, a bus factor of five means that five people would have to disappear before the project is at risk. A bus factor of one means that if one person knows everything, once they’re gone, you’re project is in critical condition.

The lower the bus factor, the more risky the project. If one person holds all the critical knowledge, then losing that person would cause delays, errors or even complete failure.

How to Avoid It

To avoid a bus factor of one, an organization should commit to knowledge sharing such as:

  • Code Reviews
  • Pair Programming
  • Documentation
  • Cross training
  • Mentoring