The scope and purpose of this SAE Recommended Practice is to provide a classification system for deformation sustained by trucks involved in collisions on the highway. Application of the document is limited to medium trucks, heavy trucks, and articulated combinations. The TDC classifies collision contact deformation, as opposed to induced deformation, so that the deformation is segregated into rather narrow limits or categories. Studies of collision deformation can then be performed on one or many data banks with assurance that data under study are of essentially the same type. Many of the features of the SAE J224 MAR80 have been retained in this document, although the characters within specific columns vary. Each document must therefore be applied to the appropriate vehicle type. It is also important to note that the Truck Deformation Classification (TDC) does not identify specific vehicle configurations and body types. The TDC is an expression, useful to persons engaged in vehicle safety, to appropriately describe a collision-damaged truck with conciseness in oral and written communications. The TDC is also a research tool; however, it has not been designed for use in impact energy computation. The research community is cautioned not to attempt direct conversion calculations from the TDC to energy equivalents required to duplicate the damage. The system consists of seven alphanumeric characters arranged in a specific order to form a descriptive composite of the vehicle damage (see Figure 1). The characters describe the principal force direction, location, specific area, type, and extent of damage. The individual character positions are referenced by column number for identification. The definition of each classification is provided in subsequent sections.