The bus factor measures how many people in your corporation need to be run over by a bus before you go out of business. If you have a key player who’s indispensable, then your bus factor is 1.
To raise the bus factor, you must make sure that important knowledge is shared and accessible to whoever needs it.
Don’t document your processes to the brink of boredom or maintain an internal wiki the size of Wikipedia itself. Build a learning organization that encourages people to share with colleagues, allocates time for research, designs for change and accepts automation as documentation.