Depending on speed, road curvature and vehicle properties, Heavy Goods Vehicle (HGV) combinations exhibit a phenomenom called High Speed Outside Offtracking. This means that the rearmost axle of the trailer/trailers does not follow the lateral path of the truck tractor unit / lorry, but may travel significantly (up to one or a few meters) away from the curve center. Hence, narrow lanes on sharp curves are / should* be designed a few meters wider than on straight road.