Age bin

I think the average Australian would have a better idea of what was signified by the various threat levels if the idea was brought more into the mainstream of everyday life - if, for example, it suggested what you should put on when you woke up in the morning.
Threat level one  - White trousers - god's in his heaven and all's right with the world
Threat level two - Black trousers - occasional episodes of pissing yourself with fear, but manageable
Threat level three - Brown trousers - sphincter-disabling terror
Threat level four - Nothing - running naked through the streets howling and envying the dead
It's disability-friendly, too, in that the blind could navigate the whole system simply by smell.