Back when I was in high school, I was mystified and very annoyed when school bus manufacturers started installing very bright strobe lights on top of their buses. Here you have a vehicle that is eight feet wide, thirty-five feet long, ten feet high, has lights all over, and is painted BRIGHT YELLOW. Anybody who manages to run into a school bus probably doesn't deserve a driver's license in the first place. Do they honestly think that adding a strobe light is going to significantly increase its visibility? In the early morning hours, when other drivers' vision is adjusted to the darkness, the strobes aren't just bright, they're blinding.
Now, apparently, the trend has spread. I first noticed it on garbage trucks. Now, I can understand the need for flashing yellow lights on the back of a garbage truck. While they move around their routes, they stop and go a lot, which can create a legitimate risk for surrounding drivers. As I drive down the highway on the way to work at 70mph+, I see garbage trucks (also barreling along at 70mph) with their lights flashing away.
Similar, but even more annoying flashers have now appeared on run-of-the-mill semis. Why does a semi need a bright, flashing yellow light, when it already has six tail lights, plus all the other decorative lights?
I understand the desire to ward off rear-end accidents. However, I can count on one hand the number of rear-end accidents I have seen in my life that involve a semi. Why? Because truck drivers tend to give themselves a lot more following room, which means that they rarely make sudden stops. The people who are following too closely behind generally have enough warning to slow down in time.
I wonder as well whether such lights are creating more risk than they are averting, by creating a distraction for drivers. Sure, that flashing yellow light might slightly increase safety for the one person directly behind the semi. But what about the couple dozen other drivers who are three lanes over, and are only distracted and annoyed by it?