1 Tons and weigh station check points

A friend of mine owns a trucking company and has their own personal tractor trailer cab to tow their 5th wheel. This cab is not commercial registered as they don't use it to tow anything in the business and only the 5th wheel. They don't go through weight stations since the truck does not have DOT numbers on it.

I asked them and they said unless the truck is registered as a commercial vehicle and has DOT numbers it does not have to stop at weigh stations.

So only commercial vehicles have to go through.