The HSE endorse the HazOff campaign
"Health and safety law requires you to carry out a risk assessment and to do what is ‘reasonably practicable’ to protect people from harm. The use of a vehicle's hazard warning lights on event sites may be appropriate in some instances eg when stationary to warn that it is temporarily obstructing traffic. However, other measures such as the combination of dipped headlights and warning beacons are often more appropriate when the vehicle is moving as they ensure pedestrians and other drivers are able to see the intended movement of the vehicle via its indicators."
Adrian TinsonHMI Health and Safety,Health and Safety ExecutiveEntertainment & Leisure sector