Figure 1 [Günter Huber]

If we are talking about insulating a building, it may well be true that more is better, but there are other rules that need to be observed in the transportation industry. With this height, you only need to think of crosswinds. And a headwind will also present problems. While it is true that the boards would cause little damage if they fell onto the road, any driver following the truck would instinctively take avoiding action which would represent a risk to both the driver and any other road users.