LTL or Less Than Truckload shipping is the transportation of relatively small freight. The alternatives to LTL carriers are parcel carriers or full truckload carriers. Parcel carriers usually handle small packages and freight that can be broken down in to units less than 150 pounds. Full truckload carriers move freight that is loaded into a semi trailer. Semi trailers are typically between 26 and 53 feet and thereby require a substantial amount of freight to make transportation economical.
Less Than Truckload shipping is a thin-margined business, so costs must be minimized. Two of the biggest costs for Less Than Truckload shippers are fuel and labor. Many Less Than Truckload shippers have unionized labor, therefore labor costs are relatively fixed, and so minimizing fuel usage is a significant goal. This translates to maximizing the utilization of every trailer for every mile driven. Ideally, every trailer carrying freight would contain a maximum level of freight by both weight and volume. The weight and volume characteristics of a set of freight is referred to as freight mix.