HHG stand for House Hold Goods.It is a mileage calculating system to determine the miles between pick up and delivery locations. It is an old out of date mileage guide,because they determine mileage based on the absolutely shortest route between the cities involved.
They will use local and even county roads to save miles.
Most companies these days use the Rand Mcnally mileage guide which is the practical miles. HHG is usually much shorter but will take much longer. Roberts Express used to use HHG but after many minor rebellions they changed.Example is one guy I know was on a run going into Lansing Michigan. His pay was based on 320 miles of HHG routing.but his routing was on Rand Mcnally, when he came up on 320 miles, he stopped with 45 miles to go and refused to go any further.
Can you blame him? I think his action spread through the fleet and that started the change.