Do you mean,
loading it while parked on the road, as opposed to
loading it while parked on private property, as opposed to actually
hauling it somewhere?
I can't imagine there'd be any difference at all, from a "DOT" standpoint. Once you get on the road and moving, it's going to have to comply with their rules (whatever they may be, as Mitch points out.) Now, the regular police may have some other concerns as far as your impact on traffic while you're loading, or something. I don't know.
Did you run into a specific problem?