Regulation 113 Stopping of engine when stationary
(1)
Subject to paragraph (2), the driver of a vehicle shall, when the vehicle is stationary, stop the action of any machinery attached to or forming part of such vehicle so far as may be necessary for the prevention of noise or of exhaust emissions .
(2)
Paragraph (1) does not apply—
(a)
when the vehicle is stationary owing to the necessities of traffic;
(b)
so as to prevent the examination or working of the machinery where the examination is necessitated by any failure or derangement of the machinery or where the machinery is required to be worked for a purpose other than driving the vehicle; or
(c)
in respect of a vehicle propelled by gas produced in plant carried on the vehicle, to such plant.