There is some info on this on the DFT website on "Safety at Streetwirks and Road works" - briefly, that vehicles must: 1. be of a conspicuous colour 2. have one or more roof mounted beacons operating 3. display a keep Right/Left sign must be displayed for drivers approaching on the same side of the carriageway, indicating which side that they should pass (this sign should be removed or covered when not required) pm me if you want more on this

My interest is roadside vehicle breakdown, hence the bias in the following response: I recommend you look at PAS43:2008 "Safe working of vehicle breakdown, recovery and removal operations. Management system specification" http://shop.bsigroup.com.../?pid=000000000030165343 In this document you will find a lot of good advice for vehicle markings, aimed at people working at the side of the road. It is useful not just for breakdown operatives, but also for anyone working in a high risk roadside operation. Another source of information is "Safety at Street Works and Road Works: A Code of Practice" (Paperback) by Transport & Regional Affairs Committee Environment (available from Amazon if nowhere else). Jointly compiled by the Scottish Executive, National Assembly for Wales and Department for Transport, Local Government and the Regions, the revised edition of Safety at Street Works and Road Works aims to ensure a consistent and safe approach to signing, lighting and guarding of works. The Institute of Vehicle Recovery (IVR) has published a series of videos to help train roadside technicians, including "Life on the edge 6. Roadside Technicians:It’s your call". This deals specifically with the safety of people involved in roadside recovery operations. (Available from Tel: 01895 436426 email:mail@theIVR.com.)