In this Part of this Act and Schedule 5 thereto, unless the context otherwise requires, the following expressions have the meanings hereby assigned to them respectively, that is to say—
" full licence " means a heavy goods vehicle driver's licence other than a provisional licence;
" heavy goods vehicle " means a vehicle of any of the following classes which is constructed or adapted for hauling or carrying goods or burden of any description, that is to say, a heavy locomotive, a light locomotive, a motor tractor, a heavy motor car and a motor car so constructed that a trailer may by partial superimposition be attached thereto in such a manner as to cause a substantial part of the weight of the trailer to be borne thereby;
" prescribed " means prescribed by regulations under section 119 of this Act;
" traffic commissioners " has the same meaning as it has for the purposes of Part III of the Road Traffic Act 1960.