I note most of my previous cars manuals have said "At load/speed".
My car does 100 miles a day and 90+ of that is at (ahem) 70mph on the motorway, though there are rarely more than 2 people in the car and often only one.
My last set of tyres was noticeably worn at the outer edges, particularly on the front, though they were actually under-inflated for a while (when I checked them they were only 30psi).
I'm certainly going to put a bit more air in, but should I run it at the loaded recommendation, half way between, or what?