Real ITSM priority starts at zero and goes up
Why do most incident priority systems go from 4 (low) to 1 (high)?
What does zero mean? What does 5 mean?
Just when you thought you had seen the worst thing that can go wrong, something comes along that makes all past priority 1 incidents look mild. How can you communicate this?
Real ITSM does things differently to, say, ITIL.
Because Real Priority (also known as Care Factor) is measured by the number of metaphorical fans that are being hit by effluent, it starts at zero and goes up. What do you think of that idea?
This is much more logical than other systems where 1 is highest. Just when you thought you had seen the worst thing that can go wrong, something comes along that makes all past priority 1 incidents look mild. How can you communicate this? With Real ITSM, you simply assign it a priority that is one higher than any previous incident.
Extract from Introduction to Real ITSM
Just like fire brigades with their "three alarm" fires.
Made in New Zealand 
