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  • claremayell

What's the Bus Factor for your Projects?

Updated: Mar 4, 2021

This week we are considering the concept of a project's 'bus factor'.

‘Bus factor’ is derived from answering the following question for each member of a project team:

  • what would happen to the project in the event that they get hit by a bus

It acts as a measure of the minimum number of people who could disappear before a project was so badly impacted it could not continue. A slightly harsh definition from a Silicon Valley website is:

  • the number of people that need to be hit by a bus before their project is dead

A bus factor of one, is not ideal at all – it implies a single person lost to the project could cause it to stall or stop. The lower the number, the more at risk your project is of being impacted.


The ‘bus factoris not a new concept. Its origins are in software development but essentially applicable to any project.

It provides a scale of the risk resulting when members of project teams do not share information and capabilities. This lack of sharing puts the reliance disproportionately with a small number of key people - causing a disproportionate impact if those people disappear.

In reality, events far less dramatic than vehicular impacts cause issues. Common situations such as someone on an extended holiday, unexpected absence due to health, family situations, getting a new job apply. Often the rest of the team struggle to identify what that person was working on, how far they have got or where to find the key information.

Why is this? Often there is no centralised repository, details stored on an individual’s local files or even are just in team members’ heads or maybe. Processes are not robust or enforced also contribute. Examples include critical components, documents or work that are undocumented, never shared, encrypted, obfuscated, unpublished, or otherwise incomprehensible to others.


It is uncomfortable to think about your team members disappearing, but a high bus factor is considered a must for resilience. Many individuals need to know enough to carry on with the project and make it succeed even in very adverse events.

So how can this be achieved:

  • SHARING: Consider how you can share information more widely across the entire team. Understand how data and information could be stored more centrally

  • DOCUMENTING: Consider how anything key to the project can be fully documented, kept up to date and stored in a location that can be accessed by others

  • SIMPLIFYING: Standardising processes can increase the bus factor

  • UPDATING: regular briefing style meetings for team members decreases the risk and can increase collaboration and sharing

  • KNOWLEDGE: spreading knowledge more widely avoiding silos of information will help to increase the bus factor

  • CONTINGENCY: identifying the key roles or capabilities that could really hurt the progress of your project. Ensure there is some contingency is available in both personnel and skills

Overall, the start point of increasing the bus factor is understanding exactly what the key areas of your project are to ensure its resilience. You will then be ready to minimise the impact of any accidents if that bus does come rolling by!


Additional reading here:

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