"There are no cashiers on duty" 23 Jul 2007

Usable Help has a nice little anecdote that demonstrates why stating the facts isn't always enough:

"The other day I visited The Art Institute of Chicago and parked my vehicle in the Grant Park underground parking garage...As I removed the entrance ticket from the automated dispenser, I experienced a problem that reminded me of a lot of software documentation.

"As soon as I removed the ticket a recorded voice said 'There are no cashiers on duty.'

"'Um, OK,' I thought to myself, 'So what?' It took me a few seconds to surmise that the point of the announcement must really be that I should pay for the parking before I get in my car to leave, because there is [no] person at the exit whom I can pay."

What an unhelpful message. Sure, it's factually accurate, but it is also extremlely unhelpful in that it requires the listener to work out why this information is being offered and what to do with it thereafter. As Usable Help points out "Pay at the automated kiosks before returning to your car" is a much more informative alternative.