In road transport, an oversize load is a load that exceeds the standard or ordinary legal size and/or weight limits for a truck to convey on a specified portion of road, highway, or other transport infrastructure, such as air freight or water freight. In Europe, it may be referred to as special transport or heavy and oversized transportation. There may also be load-per-axle limits. However, a load that exceeds the per-axle limits but not the overall weight limits is considered overweight. Examples of oversize/overweight loads include construction machines, pre-built homes, containers, and construction elements.

A hydraulic modular trailer (HMT) is a special platform trailer unit which feature swing axles, hydraulic suspension, independently steerable axles, two or more axle rows, compatible to join two or more units longitudinally and laterally and uses power pack unit (PPU) to steer and adjust height. These trailer units are used to transport oversized load, which are difficult to disassemble and are overweight. These trailers are manufactured using high tensile steel, which makes it possible to bear the weight of the load with the help of one or more ballast tractors which push and pull these units via drawbar or gooseneck this combination of tractor and trailer is also termed as heavy hauler.