For what it's worth, the US military often references MIL-STD-1472 [1] to frame general design requirements for pretty much anything that involves direct human interaction.
[1] http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=36...
[1] http://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=36...
Just glanced through it, and saw this:
5.4.2
Orientation.
Labels and information thereon (i.e., words and symbols) shall
be oriented horizontally to read from left to right. Vertical
orientation, reading from top to bottom, may be used only when
labels are not critical for personnel safety or performance and
where space is limited. Where vertical orientation is necessary,
the characters shall be readable in an upright orientation as
depicted on figure 31. Sideways text and text read from bottom
to top are unacceptable.
It is also amazing how much longer it takes me to read a label when letters are arranged vertically but not sideways. Sideways and vertical is quicker for me.
I imagine that alone would be quite useful in emergency situations, or even in general loading/unloading operations.
My wife works for a shipping company, and unless it's on a pallet, it is likely to be orientated incorrectly on at least one of the legs of its journey.
Great find!
ps I'm probably the only person here using safari, but the page to load the PDF didn't load for me so here's link to latest revision: http://quicksearch.dla.mil/Transient/72FC2386C1C2425E8298D6C... (2012).