Non-trucking liability policies (see separate article) cover you when you deviate from business.  If, for example, you take a route home that is slightly longer than “necessary”, you do any personal business, no matter how minor, along the way, you visit someone along the way, you take longer to make the trip than the insurer believes you should have taken, or you pulled your own trailer to the point of delivery (and thus are not owed a ride home by any trucking company), non-trucking liability is appropriate.  Bobtail insurance, on the other hand, covers you while you are on “business” but not covered by a motor carrier’s policy because you are not actually pulling one of its trailers.