To further complicate matters, if some of the flasher lamps on the vehicle are burned-out, then it may appear that the vehicle driver is signalling a turn when they are not. When the amber 4-way emergency / hazard flashers are on, it also makes intentional use of the turn signals non-apparent. Additional rational for this can be found on the HazardsOFF web site.
In an effort to homogenize the use of flashers at the appropriate times, a group of UK event organizers have started a campaign to get uniform policies throughout the event work staff to NOT use flashers.
Visit the HazardsOFF web site of more information, window stickers, policy advice, and more.