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Vishnu Haridas
Vishnu Haridas

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What is the "Bus Factor" of Your Project?

(Also posted in my personal blog. Cover photo by Haidan on Unsplash)


I came across the term โ€œbus factorโ€ a couple of years ago, and since then I always keep an eye on the bus factor of the projects or other mission-critical things in my life. I always try to keep the bus factor more than one whenever possible.

Wait, wait, whatโ€™s a โ€œbus factorโ€?

From Wikipedia, the bus factor is a measurement of the risk resulting from information and capabilities not being shared among team members, derived from the phrase "in case they get hit by a bus."

The term โ€œhit by busโ€ could be any event that causes a person to disappear unexpectedly โ€” from a medical emergency to an internet blackout.

For example, imagine Alice is a very critical member of a project. Alice is the only person who knows the really important information of the project like account passwords, customer contact details, etc., that no other project members are aware of. The bus factor of this project is 1. If Alice suddenly disappears one day, the project will get stopped because of the lack of critical information required to run the project.

Meanwhile if Bob also knew the said information, the bus factor would have been 2. In this case, even if Alice disappears suddenly, the project can continue with Bob (of course, now bringing the bus factor back to 1 because Alice is now gone).

So, never make the bus factor 1. The higher the bus factor, the lower the risk.

Here is a couple of examples from my life.

When working on software projects

I always ask the developers to keep a shared sheet with all the credentials and other important information consolidated in it. This will include:

  • Account details and passwords of tools, services, or websites used.
  • Special instructions to build and deploy the project.
  • Checklists and any other important information related to that project.

So if the person who regularly builds and deploys the project disappears suddenly (either due to an emergency, or an internet blackout during the delivery time slot) someone else can refer the documents and continue working on the delivery of the project.

A very recent experience

Very recently, there was a medical emergency in my family and I had to raise a good amount of money in a very short period. I contacted my friend, and he told me that he will arrange and send the money the next day.

I quickly realized that the bus factor is just one, and canโ€™t really depend on a single person for the money in such a critical situation. I contacted several other friends, and four more friends agreed to send the money if required. Now the bus factor is improved to 5.

Unexpectedly on the next day, the first friend got into an emergency situation where his car stopped working in the middle of the traffic, had to tow it to the service station, and his whole day got ruined. He was totally unable to arrange the money on time.

Luckily my bus factor was 5, so I had 4 more persons remaining. Finally the money was arranged and everything went smoothly.

Had I kept my bus factor to just 1 in this case, I would have been doomed that day!

Another experience from a friend

One of my friends kept all her childrenโ€™s tons of childhood photos in an external hard disk. One day the hard disk fell down and gigabytes of memory got destroyed instantly! The bus factor was just 1 here โ€” if the hard disk is gone, everything is gone. If she kept another backup in a DVD, another hard disk, or uploaded to Google Photos, she could improve the bus factor many times and reduce the risk of losing all her precious memories.


So, let me ask once again. Whatโ€™s your bus factor?

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