In considering whether an operator’s licence is required, the first question is whether the operator is carrying goods or carrying passengers. For instance, a tractor unit is a goods vehicle. A tractor unit conveying empty trailers to and from the testing station amounts to the carriage of goods because ‘goods’ includes burden of any description.
The hauling of trailers by a tractor unit for the purposes of testing and repair as part of a trade or business requires an operators’ licence. A tractor unit is a separate vehicle from a trailer and can only fall within an exemption if it is proceeding to the testing station for the purpose of a test upon itself. (2002/134 WC Commercials Ltd, Booth v DPP [1993] R.T.R. 379) The Upper Tribunal has indicated that a strict approach should be taken when applying exemptions from the requirement for an operator’s licence.
Source - Introduction to operator licensing, the statutory guidance and statutory directions