Modification means any change to the original design and construction of a cargo tank or a cargo tank motor vehicle that affects its structural integrity or lading retention capability including changes to equipment certified as part of an emergency discharge control system required by 173.315(2) of this subchapter. Any modification that involves welding on the cargo tank wall must also meet all requirements for Repair as defined in this section. Excluded from this category are the following:
(1) A change to motor vehicle equipment such as lights, truck or tractor power train components, steering and brake systems, and suspension parts, and changes to appurtenances, such as fender attachments, lighting brackets, ladder brackets; and
(2) Replacement of components such as valves, vents, and fittings with a component of a similar design and of the same size.
49 CFR § 180.403
In addition to the definitions contained in 171.8, 178.320 and 178.345-1 of this subchapter, the following definitions apply to this subpart: