xmlns:atom="http://www.w3.org/2005/Atom"
21For the purposes of this Schedule measuring or testing apparatus, and any ballast necessary in connection therewith, drawn upon one wheel by a vehicle, when used solely for or in connection with testing or measurement purposes, shall not, if the wheel is fitted with a pneumatic tyre and does not transmit to the road surface a weight exceeding 2 hundredweight, be treated as a trailer.