If this sign is on the public highway, sounds like an illegal sign to me. If its for temporary works it should look like this http://www.opsi.gov.uk/si/si2002/023113ic.gif If he's just trying to reserve a bit of the public highway for himself, get onto your local Council. But be careful I had someone on the phone today who'd had paint stripper poured over their car during the night as someone took exception to them parking on 'their road'