11.—(1) Subject to the provisions of paragraph (2), and notwithstanding that such vehicles do not comply with the requirements of regulation 7 of the Construction and Use Regulations, the Department authorises the use on roads of—
(a)an agricultural motor vehicle;
(b)an agricultural trailer designed to perform functions, other than the carriage of goods, that necessitate an overall width of 2.55 metres being exceeded; or
(c)an agricultural trailed appliance,
if the relevant conditions specified in Schedule 2 are complied with.
(2) The authorisation specified in paragraph (1) applies only in so far as the width of a vehicle (including an agricultural implement which by virtue of Article 13 is treated as part of the vehicle) cannot, without undue expense or risk of damage, be reduced.