http://www.legislation.gov.uk/nisr/1981/352/madeThe Safety Signs Regulations (Northern Ireland) 1981Government Printer for Northern Ireland2016-12-22HEALTH AND SAFETY The Safety Signs Regulations (Northern Ireland) 1981RegulationsHealth and Safety (Safety Signs and Signals) Regulations (Northern Ireland) 1996Sch. 3 Pt. 1reg. 6reg. 1