Then list them in both categories...

But listing any pickup truck like a truck is an American way of listing things The vehicles sold as "pickup truck" (like Toyota or Nissan) only got that name in USA
It is very difficult to internationalize some things.
In the future, we'll probably organize categories differently, as we also have that kind of problems with small buses and motorhomes which are split between cars & buses categories.

Well, considering it's an international, not a European-only site, I believe "pickup truck" should be listed under "trucks"...

The truck section was for heavy trucks, it was made originally in european way of classifying vehicles, where there is a difference for vehicles under 3.5t and above that.

Why isn't "pickup truck" in the "trucks" section? Silly for it to be in the "cars" section when "pickup truck" has "truck" in its name...