When I was a militaryTransportation fleet manager for a six hundred vehicle fleet, I ordered DLR be used 24/7 by all drivers everywhere except in tactical situations. In two weeks we cut the vehicle accident rate by half, mostly back-up accidents. Headlights are very important aids to visible detection by other drivers, coming or going. They also mitigate against highway hypnosis accidents, big time, on long-haul trips. 4-way flashers must NOT be used frivolously, however. It makes people swear and ignore them when there really is a hazard. I am absolutely convinced that DLR saves lives!...and fenders.
Grayhound figured it out in the 1930's.
Unless impaired, most people notice 3 things - light, colour, movement. There are no guarantees (plenty of EMS vehicles parked on the side of the road still get plowed into, despite being lit up like a fireworks display), but the more of those 3 factors you can combine, the higher your on-road visiblity will be.
One of the reasons that many people don't pay much attention to these issues is the safety of modern light-vehicles (cars, and more recently, trucks). Many people now routinely walk away from crashes that were often fatal in decades past.
Rgds, D.