From wikipedia, a “Bus Factor” is:

an irreverent measurement of concentration of information in a single person, or very few people. The bus factor is the total number of key developers who would need to be incapacitated, as by getting hit by a bus, to send the project into such disarray that it would not be able to proceed

 

From my personal experience, I'd say that more than 70% of projects suffer from a bus factor of 1. It only takes one specific person in those teams to not be able to be there for the project to halt or slowly die in painful agony as people try to makeup for lost knowledge.

How do you recognize the bus factor?

in your mind, go through each person in your team and ask yourself if

the project could go on pretty much as usual if they were fired tomorrow. (fired is important because people who leave in good terms can still play ball and get you through tough stuff they worked on through phone conversations).

If you say “no” or even hesitate about the answer, you’ve found the bus factor in your team.

How do you get rid of the bus factor?

Most of the collaboration techniques you’ll find in many agile methodologies like XP try to solve the idea of the bus factor, but you don’t have to be agile to use those techniques.

 

• Use daily standups to share critical information
• program in pairs every once in a while, or at least on key components of the system
• do code reviews on every piece of code that gets checked in
• do weekly half hour or one hour presentations by team members about interesting stuff they did this week
• Ask the bus factor carrier to teach someone else from the team to do their work and vice versa. Tell them that next week they will be working alone on that material so they should get ready for that by working together on it.

The biggest bus factor is you

As a team leader, you might just be the biggest bus factor carrier of them all. What happens if you get fired tomorrow? can the team go on without you?

Your biggest challenge as a team lead, over a long period of time would be to make yourself dispensable – to make the team mature enough to continue on day to day things without needing you. Removing yourself as a bottleneck is one of the best things you can do for yourself and your team.