If it appears to the Traffic Director for London, or some person authorised by him, essential in the interests of the expeditious, convenient and safe movement of traffic, or of the provision of suitable and adequate parking facilities on the highway, or for preserving or improving the amenities of the area through which any road affected by this Order runs, and after consulting with the Commissioner of Police of the Metropolis, he may modify or suspend any provision of this Order, save that no modification shall make an addition.